Growing For Quality. A Good Agricultural Practices Manual for California Avocado Growers Version 1.0

Transcription

1 Growing For Quality A Good Agricultural Practices Manual for California Avocado Growers Version 1.0

2 The California Avocado Commission (CAC) received funding and other support for this project from several sources including: The Governor s Buy California Initiative; the California Department of Food and Agriculture; the U.S. Department of Agriculture; and the University of California. We gratefully acknowledge the contribution of all of these organizations.

3 California Avocado Commission Grower Best Practices Manual Contents Fruit Quality and Safety... 1 Common Avocado Quality Problems... 2 Orchard Management... 3 Fruit Rot Management... 3 Disease Management... 4 Insect Management... 5 Vertebrate Pest and Snail Control... 7 Nutrition... 8 Irrigation... 8 Harvesting and Field Handling... 9 Hygiene and Food Safety Appendix 1: Disease Management Appendix 2: Insect Management Appendix 3: Vertebrate Pest And Snail Control Appendix 4: Harvesting and Field Handling Appendix 5: Hygiene and Food Safety Good Agricultural Practices Self-Audit... 67

4

5 California Avocado Commission Grower Best Practices Manual FRUIT QUALITY AND SAFETY Premium quality fruit is vital if California is to retain its leading position in the market. As an industry, we want to deliver: Quality fruit that consumers will want to buy again and again because they are so impressed by the look and taste. Fruit that is safe to eat without any perceived threat of foodborne illness. We want to deliver quality fruit to our consumers that they are not just happy to buy, but that they will want to buy again. Since fruit quality and safety are at least to some extent predetermined in the orchard, these general guidelines will help growers manage and improve fruit quality in the market. 1

6 Common Avocado Quality Problems Fruit is extremely sensitive to the environment in the orchard, particularly during handling at harvest time. While, in general, California avocados may have a quality advantage over their counterparts imported from other countries, poor orchard practices can make fruit SUSCEPTIBLE to these common quality problems: 1. External blemishes caused by orchard pests, sunburn, wind, and limb-rub. 2. Mechanical damage caused by rough handling by pickers, packers, produce workers, and customers. 3. Rots caused by decay organisms entering through injuries in the skin or stem end of fruit. 4. Pulp injury resulting from excessive storage duration, mineral imbalances, or improper storage temperatures. 5. Off flavors resulting from sunburned fruit, excessively late harvest, high temperatures during harvest or handling, and/or excessive holding periods after harvest. The Best Management Practices described in this manual will help growers avoid these problems and will help maintain California s position as a leader in fruit quality. The California Avocado Commission is developing similar manuals for the packing and retail sectors of our industry, to achieve a seamless system of fruit quality improvement and food safety assurance. Avocados ready for harvest 2

7 ORCHARD MANAGEMENT Fruit Rot Management Fruit rot diseases are a serious problem to the avocado industry. These diseases are usually caused by fungi and are often carried over from year to year on dead or infected plant parts (stems, twigs, leaves, and fruit). While the current crop can be infected at any time after set, infections may not be visible until after the fruit is harvested and ripens. To reduce the source of fruit rot infections it can help to: Remove dead fruit, branches, and leaves trapped in the canopy. Use a mechanical chipper to speed the breakdown of excessive pruning wood and leaves into mulch, and dispose of excessive windfall fruit on the orchard floor. Whole dead branches and fruit left in the tree and on the orchard floor produce spores which may lay dormant on fruit surfaces. These spores are the main source of fruit rot organisms on fresh avocado fruit after harvest. 3

8 Disease Management 1 It is important for growers to manage the following avocado diseases which directly impact fruit quality: Disease Damage Caused Treatment Options Phytophthora Root Rot 1 Avocado Stem Canker or Collar Rot 1 Avocado Sunblotch Disease 1 Leaf loss and/or small, pale leaves; heavy crop of small fruit, increased sun damage; possible tree death. Leaf loss, heavy crop of small fruit, increased sun damage, cankers usually at or below soil level. Small or distorted fruit, thinning of canopy; trees may appear stunted and sprawling. Site selection and soil preparation, good drainage, certified disease-free nursery stock, disinfect orchard equipment, coppersulfate boxes or baths at orchard entrances, chemical treatments. Certified disease-free nursery root stock, avoid severe pruning in infected orchards, disinfect tools, remove fruit lying on ground. 1 Treat pruning, cutting, and injection tools with 15% bleach solution between trees; run lab test to detect sunblotch viroid before grafting. 1 See Appendix 1 for more information regarding disease causes, symptoms, and treatments. 4

9 Insect Management 2 It is important to maintain good pest control in the orchard, especially for thrips, persea mite, and avocado worms (lepidopterous larvae). Consult a qualified Pest Control Advisor or University of California (UC) Farm Advisor before applying pesticides. Choose the least harmful material available so as not to disrupt natural enemies and biological control. Note: Provide employee pesticide safety training and proper apparel. 3 Follow all preharvest intervals on the pesticide label. Photo: Thrips can cause severe external damage to fruit, resulting in downgrade at packing. Insect Damage Caused Treatments Thrips Persea Mites Avocado Worms (Lepidopterous Larvae) Cause external, cosmetic damage to fruit that detracts from quality. Tree stress, small fruit, sunburned fruit, poor fruit quality. Superficial skin damage that may allow rot organisms or food-borne illness pathogens to enter the fruit. Franklinothrips adults or green lacewing larvae, Veratran D, Success 2 SC, or Agri- Mek +NR415 oil. Predatory mites, NR415 oil. Monitor moth flights with pheromone traps. 2 See Appendix 2 for more information regarding insect control. 3 See Worksheet 10 Acknowledgement of Pesticide Safety Training. 5

10 Insect Damage Caused Treatment Options Omnivorous Looper Avocado Amorbia (Amorbia cuneana) May damage leaves and fruit; young fruit becomes distorted; surface of larger fruit is scarred, providing entry point for rots. Larvae feed on fruit skin and cause scarring. Trichogramma platneri wasps, Bacillus thuringiensis (Bt) sprays. Trichogramma platneri wasps, tachinid flies, Bacillus thuringiensis (Bt) sprays. Omnivorous Looper Avocado Amorbia Photos by Max Badgely 6

11 Rats Ground Squirrels Gophers Deer and Rabbits Vertebrate Pest and Snail Control 4 Pest Damage Caused Treatment Options Brown Garden Snails (Helix aspersa) Chew fruit; may transmit diseases to humans or livestock. Gnaw on bark, eat leaves, burrow around roots, may gnaw on plastic sprinkler heads and irrigation lines. Damage roots on young and old trees. Damage leaves and bark of young trees. Scar immature fruit, attack leaves of young trees, may kill small grafts. Clear brush and woodpiles in/near orchard; remove fallen fruit; thin or remove climbing hedges; store pet food in rodent-proof containers; do not leave leftovers in pet dishes; cover garbage containers tightly; seal cracks and openings in buildings; use snap traps indoors and bait blocks outdoors. Remove brush piles and debris; destroy burrows; use anticoagulant baits; fumigate in spring (gas cartridges); trap with box traps or Conibear traps. Use traps; bait tunnels with specially formulated baits. Spray leaves with deer repellant; use 1 mesh chicken wire to protect trunk for first year only; fence in the grove. Decollate snails (Rumina decollata); chemicals (iron phosphate or metaldahyde). 4 See Appendix 3 for detailed information on vertebrate pest and snail control. Contributor: Terry Salmon 7

12 Nutrition 5 Try to achieve high fruit calcium levels through judicious fertilizer management, avoiding tree stress and alternate bearing. Be cautious of having excessive nitrogen and potassium levels in trees. Excessive levels of these nutrients may result in poor fruit quality and rot susceptibility. See your UC Farm Advisor or commercial field consultant for recommendations for your grove. Irrigation 6 Ensure adequate irrigation over the flowering period, during fruit set, and while the fruit matures on the tree. This can be done by monitoring soil water levels or using water budget irrigation scheduling based on CIMIS data and avocado crop coefficients, available from your local farm advisor. Stress conditions during any of these periods can produce fruit with inferior postharvest characteristics. Good irrigation practices also reduce the development of ring-neck necrosis (death of fruit stems), which may be associated with small fruit, poor quality, and the entry of rots. Ring-neck necrosis 5 Contributors: Ben Faber, David Crowley, Carol Lovatt 6 Contributors: Ben Faber, Laosheng Wu, David Goldhammer 8

13 Harvesting and Field Handling 7 If pesticides were used during crop production, doublecheck orchard treatment records before picking fruit to ensure that all preharvest intervals (chemical withholding periods) required by law have been adhered to. When harvesting and handling fruit, it is essential to minimize weight loss, field heat in fruit, and damage to fruit. 1. Wet Fruit: To prevent fruit from developing unacceptable levels of rots, avoid handling wet fruit at harvest. Do not pick fruit until after any rain or dew has dried on the surface of the fruit. The fungi that cause stem-end and body rots on avocados spread their spores during rain by water splashes. Take extra care to minimize handling damage to fruit, especially during harvesting after heavy rain. 2. Temperature: If possible pick fruit when the air temperature is below 90 F and avoid picking 1-2 hours either side of midday peak temperatures if it is expected to exceed 90 F. If the temperature forecast for the day exceeds 90 F, hang a thermometer in a shaded area of the orchard and monitor the temperature during picking. As temperatures approach 90 F, pick shaded fruit and use bin covers to reduce sunlight on fruit. During very warm weather, transport fruit to the packing facility as quickly as possible. 7 See Appendix 4 for more information on harvesting and field handling. Contributor: Mary Lu Arpaia 9

14 3. Picking Method: Fruit should be picked using hand clippers or picking poles. Clip the stem to leave a button of 1/8 inch or less. Snap-picking of fruit may be considered during part of the season and in certain areas. Solicit advice from your fruit handler. 4. Ground Contact: Fruit which has been in contact with the ground should be handled separately (see Hygiene and Food Safety). This includes windfalls and fruit on lower branches that have touched the ground. 5. Damaged Fruit: Select-pick fruit and do not place fruit with fresh, visible damage into field bins as this fruit will produce excess ethylene gas and may be a food safety hazard. Pay particular attention to separating and dumping rodent-damaged fruit as this fruit poses a high food safety risk. 6. Picking Bags and Equipment: Keep clippers and bags clean and in good working order. Minimize the distance that pickers have to walk with a full bag by placing field bins close to the pickers. Sanitize equipment before moving into a new grove. Use equipment and picking bags that are clean and in good working order. Minimize the distance between pickers and field bins. 10

15 7. Field Bins: Bins should be rigid enough to prevent flexing and consequent peel damage caused by fruit rubbing together. Be sure your handler keeps bins clean and free of protrusions such as nails. Place bins in a cool, shaded area with good air movement, or construct a covered area in a shaded part of the orchard using a tarpaulin or shade cloth stretched between poles. Cover bins to reduce water loss. 8 Rigid bins prevent peel damage caused by fruit rubbing together during handling and transportation. 8. Transport: To avoid water loss and a decline in fruit quality, do not hold fruit too long after harvest. If possible, transport fruit to the packinghouse twice daily, but at least daily. Ideally, do not leave bins in the orchard for more than 8 hours and do not store full bins overnight in the field. Inspect trucks/trailers before loading fruit. Covering bins during transport can help minimize water loss and exposure to direct sunlight. Maintain access roads to minimize fruit damage during transport. 8 See Good Agricultural Practices Self-Audit Form. 11

16 Harvested fruit should be transported to the packinghouse as quickly as possible to prevent high temperature buildup and subsequent deterioration of quality. 12

17 HYGIENE AND FOOD SAFETY 9 Every year in the United States foodborne illnesses result in deaths and economic losses. The key to preventing foodborne illnesses is preventing food contamination. Once fruit is contaminated, pathogens are very difficult to remove. 1. Control wildlife in the grove. Keep pets out of the grove and fruit handling areas. 2. Minimize fruit contact with the ground. 3. Prevent fruit contact with water that has been contaminated by human or animal waste. 4. Use properly composted manure Prevent fruit contamination by workers. Teach and enforce proper handwashing techniques. Prevent anyone with an infectious disease, diarrhea, or open lesion (boil, sore, infected wound) from having direct contact with fruit. Provide adequate toilet and handwashing facilities for ALL workers. Clean toilets, sinks, and handwashing stations regularly Ensure safe disposal of waste from toilet facilities. 7. Promote cleanliness at U-Pick fruit operations. 8. Keep field bins, picking bags, and harvesting tools clean Contributors: Mike Villaneva, Mary Lu Arpaia. See Appendix 5 for more information on Hygiene and Food Safety. 10 See Worksheet 1 for more information on properly composted manure. 11 See Worksheet 2-4, Field Sanitation and Worker Hygiene logs. 12 See Worksheet 5, Harvest Tool Cleaning Checklist. 13

18 14

19 APPENDIX 1 DISEASE MANAGEMENT It is important for growers to manage avocado diseases that have a direct impact on fruit quality. Phytophthora Root Rot 13 Phytophthora root rot (PRR) caused by Phytophthora cinnamomi Rands is very common in California orchards. PRR is considered the most important and most widely distributed disease of avocados in California. It has been estimated to affect between 60-75% of the orchards and causes losses in excess of $40 million annually. If not controlled it will cause tree decline accompanied by leaf loss (defoliation). When in decline from this disease, trees may have significant foliage (leaf) loss and may set a heavy crop of small fruit, much of which may be sun damaged. Symptoms The first signs of PRR are manifested in the tree canopy. The leaves are small, pale green, often wilted with brown tips, and drop readily. In contrast to Phytophthora stem canker (next section), new growth is usually absent. During early infection trees may flower profusely in spring and set a large crop of small fruit. Eventually shoots die back from the tips and the tree is reduced to a bare framework of dying branches. Tree death may take from a few months to several years depending on soil characteristics, cultural practices, and environmental conditions. The small feeder roots on diseased trees may be absent in the advanced stages of decline. When present, they are usually dark brown, brittle and decayed, in contrast to healthy trees, which have an abundance of creamy-white feeder roots. 13 Contributors: John Menge, Lawrence Marais, Gary Bender, Ben Faber 15

20 During early Phytophthora cinnamomi infection, trees may flower profusely in spring and set a large crop of small fruit. Eventually, shoots die back from the tips, leaf cover becomes sparse, and the tree is reduced to a bare framework of dying branches. The remaining fruit is highly susceptible to sunburn. Healthy feeder roots of avocado (left) are mostly creamy white versus Phytophthora cinnamomi infected roots (right), which are often dark brown, brittle, and decayed. 16

21 Causal Organism and Epidemiology Soil moisture is the primary environmental factor influencing PRR development. High soil moisture stimulates the development of fungal fruiting structures called sporangia and the release of zoospores (swimming infectious agents) in the soil. However, low moisture and excessive soil salt can injure avocado roots causing them to exude substances which attract zoospores and may also cause infection. Where P. cinnamomi is not native to an area, the primary method of introduction of the disease into orchards is by infected nursery trees. Once in the orchard, PRR can be spread by infected soil on shoes, tools, vehicles, picking boxes, ladders, and storm water. Disease Management Since no definitive measures have been found to completely control PRR, an integrated approach to managing the disease has been found to be most effective. This approach includes prevention, cultural practices, and chemical treatment. These aspects are discussed below. Site Selection and Soil Preparation Orchard soil should be prepared well in advance of planting. Severe PRR is associated with soils that have poor internal drainage, are less than 3 feet deep, have hard pans, clay pans, and high clay content. These soils are conducive to inoculum build-up and infection of roots and should be avoided. Less hazardous soils with a clay-loam texture and depth of 3-5 feet should be deep ripped and provision should be made for drainage. Saline soils and soils with high salinity potential should also be avoided, since not only does salinity retard growth and reduce yield, but it may exacerbate avocado root rot. On sloped land, the construction of interception and diversion drainage ditches or provision of water-tight drain pipes which drain rain water away from the orchard will help prevent the introduction of P. cinnamomi into lower lying areas. 17

22 In heavy clay soils, trees can be planted on mounds or ridges. This practice has been found to increase the survival rate of young trees. Ridges and mounds gather and incorporate surrounding topsoil, improving topsoil depth and drainage. The addition of organic material, mulches, and gypsum to the soil may increase the soil s suppressiveness of PRR. Disease-free Nursery Trees Historically, diseased nursery stock was the major source of spread of PRR in California. Now, commercial nurseries have certification programs which ensure that growers can purchase PRR-free trees. Irrigation and Irrigation Water The avocado tree is extremely sensitive to water-logging due to the high oxygen requirement of its roots. With excessive soil moisture, root growth ceases and the stage is set for large-scale destruction of feeder roots. The use of tensiometers or other tools to schedule irrigation is advised. Water from deep wells is unlikely to be contaminated with P. cinnamomi, while water from reservoirs and canals can be a source of infection. If contamination is known or suspected, water from these sources should be treated with chlorine to eliminate inoculum. When an infected area is identified in an orchard, the diseased trees and the trees at the margins of the diseased area should be irrigated with caution, avoiding over-irrigation. Careful irrigation can retard the spread of the disease and will often prolong the life of affected trees. Orchard Sanitation The most economical method of controlling P. cinnamomi is to exclude the disease from clean avocado orchards. Movement of soil and water from diseased orchards into healthy ones should be avoided at all costs. The fungus readily moves from orchard to orchard in moist soil on tools, vehicles, bins, ladders, shoes, domestic and wild animals, etc. 18

23 To prevent this from occurring: Place fences and warning signs between uninfected and infected orchards. Place boxes containing copper sulfate at the property entrance and require all foot traffic to dust shoes before entering the grove. Shallow, chlorinated, or copper sulfate-treated water baths may also be placed at the entrance for vehicles to drive through when entering the premises. Always disinfect equipment after use in a diseased orchard. Dip shovels, soil augers, and trowels in 70% ethanol or rubbing alcohol before reuse. Remove severely affected trees. Resistant Rootstock A great deal of research has been conducted on detecting and developing resistant rootstocks, particularly in California, South Africa, and Israel. Clonal rootstocks such as Duke 7, Thomas, Barr Duke, and Toro Canyon exhibit a degree of tolerance to PRR compared to traditional Topa Topa seedling rootstocks. Not all of these rootstocks yield as well as the traditional PRR sensitive ones in non-infected groves. Field trials are showing that a new generation of rootstocks (Dusa, Zentmyer, and Uzi, to name a few) may offer a greater degree of root rot resistance, along with good yields, compared to currently available clonals. Trees on resistant rootstocks will survive under disease pressure when used in conjunction with the other control measures mentioned above. While clonal rootstocks have different levels of tolerance/resistance to PRR and may be expensive, they can provide a degree of insurance against devastation by PRR. Chemical Control In the 1970s and 1980s, systemic fungicides with specific activity against species of Phytophthora and related fungi revolutionized control of diseases such as PRR. The first of these compounds were metalaxyl (Ridomil ) and fosetyl Al (Aliette ). 19

24 The phosphonates, including fosetyl Al and its active breakdown products, phosphorous acid and potassium phosphite, have been effective in research trials when applied as foliar sprays, trunk paints, trunk injection, or soil application. Trunk injection, first developed in South Africa, has given good results in many avocado-producing countries. In South Africa and Australia, salts of phosphonic (phosphorous) acid, particularly potassium phosphonate (potassium phosphite), have been registered for foliar and trunk injection. A similar product has been registered for use in Israel. In most countries, trunk injection of these chemicals is the preferred method of application and is the best way to rejuvenate trees severely affected by PRR. Fosetyl Al injected into severely affected trees has resulted in nearcomplete recovery in many cases. In South Africa 1 ml of a 50% neutralized (buffered) phosphonic acid (neutralized with potassium hydroxide) is injected per meter square (10 feet square) of tree drip area; this equates to 0.5 g (0.02 oz) active ingredient per meter square of tree drip area. Injections are applied twice annually, once following the hardening off of the spring flush which occurs during and after flowering, and the second application following the hardening off of the summer flush. These two applications coincide with peak root flushes. A combination of foliar and soil applications of Aliette or phosphorous acid is often used to suppress PRR in relatively healthy groves. The current recommended treatment for healthy and lightly infected trees in South Africa, New Zealand, and Australia is a foliar application of 0.8-1% buffered phosphorous acid 4-6 times annually. Metalaxyl (Ridomil ) applied as a granular, a drench, or injected into the irrigation water has been found to be effective in some cases. However, Aliette has been found to be more effective than metalaxyl in mature orchards in California. 20

25 Avocado Stem Canker or Collar Rot 14 Avocado stem canker and collar rot are caused by Phytophthora citricola. This disease affects fruit quality much like root rot, with an abundance of small, sun-damaged fruit. In some areas P. citricola will directly infect fruit during wet winter weather, causing a rot that discolors the skin and extends into the fruit flesh. Trunk, collar and crown canker on avocado trees is generally caused by Phytophthora citricola Sawada and is especially prevalent in the cooler coastal production areas of California. P. citricola is present in approximately 90% of California avocado orchards, while disease expression itself occurs in only around 5% of these orchards. Overall appearance of canker infected trees is often similar to P. cinnamomi with heavy set of small fruit and sparse leaf cover resulting in a high proportion of sun-damaged fruit. 15 Symptoms Trunk cankers caused by P. citricola are normally found at the base of the trunk extending to a height of approximately 18 inches. The pathogen infects the crown, lower trunk, and sometimes the main structural roots of avocados of all cultivars. Cankers usually originate at or below soil level but can be found higher up in the tree if bark damage has occurred. This is because the pathogen can enter through wounds caused by pruning tools, mechanical damage caused by pickers, or even limbs rubbing against each other during wind. Canker lesions are discolored and produce a red, resinous, watersoluble exudate through cracks in the bark. This exudate often dries to form a white crystalline deposit on the bark. Cutting into a canker reveals an orange-tan to brown-pigmented outer layer of wood with a fruity odor, instead of the normal white or creamcolored tissues. Cankers have distinct reddish-brown margins from which the fungus can readily be isolated. 14 Contributors: Lawrence Marais, John Menge, Gary Bender, Ben Faber 15 See Common Avocado Quality Problems. 21

26 Foliar symptoms are similar to those caused by Phytophthora root rot (PRR), however there is usually an abundance of healthy, cream-colored feeder roots in the area of the root crown. In the case of collar rot, there always appears to be more leaf litter on the orchard floor than with root rot because collar rot-affected trees tend to develop a great deal more new flush during the growing season than do root rot-affected trees. Moderately affected trees often appear quite healthy and may persist this way for several years until the canker progresses to a stage where it starts killing the cambium tissues around the trunk. Unless the trunk is inspected for lesions (and tell-tale signs of white powdery exudates), the tree generally appears healthy. In some cases the disease can progress very rapidly, killing the tree in a few months by killing the cambium and girdling the trunk. Sometimes trees have the disease without any above ground signs of a canker. In these cases, cankers may girdle trees a few inches below the soil level before the disease is detected. P. citricola cankers usually originate at or below soil level (left), but can be found higher up in the tree if bark damage has occurred (right). Mechanical damage to the tree from pulling suckers is thought to be a major point of entry for this disease. Often there is sugary exudate (bleeding) with a distinct pocket of wet dead tissue below the damaged bark. 22

27 Typical P. citricola infection symptoms on fruit include a distinct circular brown/black area on the lowest part of the fruit. Photo: H. Ohr P. citricola may infect fruit during prolonged wet weather, particularly in northern growing regions. Fruit on the tree may be infected particularly if near or touching the soil surface on lower branches. Most damage occurs within 3 feet of the soil surface. Diseased fruit have a distinct circular black area that usually occurs at the lowest part of the fruit. While most infections occur at the bottom of the fruit, they can occur anywhere on the surface. Internally, the rot extends into the flesh, darkening it in the same pattern as the affected area on the surface. Causal Organism and Epidemiology P. citricola has been recorded on a wide range of hosts such as walnut, cherry, cherimoya and fir trees. Phytophthora canker disease is favored by excess moisture, which is essential for dissemination of the spores. Stress factors resulting from water deficit, salinity, excess fertilization, and root disease caused by P. cinnamomi are also conducive to infection by P. citricola. One of the primary ways in which the disease is spread is through infected nursery stock. Nurseries that do not disinfect irrigation water, sterilize potting media, or keep containers off the ground may be responsible for disseminating the disease. 23

28 Phytophthora canker differs from the root rot pathogen in that it infects through wounds created by gophers, sucker removal, wounds made during staking, and cold injury. It has been reported that severe pruning of canker infected trees increases their rate of demise. The pathogen can also be spread by contaminated pruning tools, harvesting equipment, and vehicles, by the shoes of pickers climbing in trees, and by rodents feeding on the roots. Disease Management The measures recommended for the control of Phytophthora canker diseases are similar to those described for Phytophthora root rot (see previous section). The use of certified disease-free nursery stock cannot be over-emphasized. Unlike root rot-infected trees that can be treated successfully to a state of near-total remission, it is very difficult to cure trees once they become infected with P. citricola. Some clonal rootstocks resistant to Phytophthora root rot, such as Thomas, may be susceptible to P. citricola. Current rootstock research in California looks simultaneously for resistance to both diseases. Chemical Control: Research results on chemical control of Phytophthora cankers caused by P. citricola have not been conclusive in California. Scraping and Painting: Greenhouse experiments at the University of California Riverside indicate that cutting away cankerous lesions on seedlings and applying Aliette as a trunk paint will arrest the infection. Scraping off cankerous tissues and painting the area with copper Bordeaux has been used in the past, but some growers have reported an increase in the spread of the disease after this treatment. Preliminary research shows that if tree surgery is followed up by treatment with Aliette or neutralized (buffered) phosphorous acid, disease spread is arrested. In much the same way, removing rootstock suckers in the field by cutting them above the ground and treating the cut surface with Aliette or neutralized (buffered) phosphorous is likely to reduce potential infection. 24

29 Pruning: Avoid severe pruning of canker affected trees. Pruning tools should be disinfected before moving to the next tree. It is important to remove leaf litter from crotches of trees and from around the base of the trunk. Water Exposure: Cankers may frequently develop on the side of the trunk exposed to sprinklers. Avoid letting sprinkler irrigation wet the crotches of trees or spray directly onto the trunks. Preventing Infection: Preventing infection is challenging because a cause is splashing of Phytophthora spores from the soil surface onto the fruit during rainy weather. Any mechanism that helps reduce splash, such as a layer of leaves or mulch, may help. Where P. citricola is a problem, fruit lying on the ground should be removed because the fungus can grow and sporulate there, providing an abundant source of new infection. Avocado Sunblotch Disease 16 Avocado sunblotch disease can also adversely affect fruit quality. Fruit from infected trees may show overall distortion, sometimes with sunken yellow and red depressions on the surface. These fruit are graded as standards and receive lower returns from the packinghouse. Sunblotch-infected trees should be removed and replaced with healthy stock. Avocado sunblotch disease is caused by an infectious ribonucleic acid (RNA) known as a viroid and has been recognized in California for over 60 years. Infected trees may have abnormal tree growth and a high proportion of small or misshapen fruit. Specific symptoms may be observed on fruit, leaves, and stems. Fruit may show overall distortion, sometimes with sunken yellow and red depressions on the surface. These fruit are graded as standards and receive lower returns from the packinghouse. 16 Contributors: J. Allan Dodds, Deb Mathews, Mary Lu Arpaia, Guy Witney 25

30 Foliar symptoms can include a general thinning of the canopy, with individual leaves showing bleaching (white patches), variegation (yellow and green patches), and distortion. Stems may also show discoloration with yellow, white, or pink streaks and in extreme cases may be completely yellow. Infected trees often appear stunted and somewhat sprawling. Fruit from avocado sunblotch-infected trees may show overall distortion, often with sunken yellow or red depressions on the surface. Foliar symptoms can include a general thinning of the canopy, with individual leaves showing bleaching (white patches), variegation (yellow and green patches), and distortion. 26

31 It is possible for trees to recover from avocado sunblotch disease. The recovered tree will have no apparent visual disease symptoms, but still carries the viroid. These trees are termed symptomless carriers. Such trees typically have very low fruit yield or at times may set heavy crops of small fruit. If symptomless trees are topworked with disease-free material, the topworked material will become infected and can exhibit classical sunblotch symptoms, thereby revealing the presence of sunblotch. If a symptomless tree is subject to a stress such as fire, or is stumped, the regrowth may once again exhibit sunblotch symptoms. Avocado sunblotch is primarily transmitted by infected budwood used in grafting. Mechanical transmission from infected to healthy trees may also occur during tree pruning. Seed and pollen can also spread sunblotch, although the rate of transmission through seed varies, with a relatively low rate of seed transmission when the seed comes from trees exhibiting symptoms. However, seed from symptomless trees have a very high rate of transmission (80 to 100%). Why this occurs is not understood. Pollen transmission has also been demonstrated using honey bees in caged trees. This implies that under field conditions honey bees could be a vector of sunblotch. There is no accurate estimate of the incidence of sunblotch in California, but there is a perception among some that sunblotch is an increasing problem in the industry. The increase is likely based in part on increased top working, tree size management, and tree injections. Sunblotch can be brought into our industry with the introduction of new varieties or rootstocks.* The extent to which sunblotch becomes a problem in the future will depend on nursery propagation techniques and grove management strategies. The sunblotch viroid can be detected in leaf extracts by a rapid lab test known as PCR. Tests of nursery mother trees and new varieties are helping to ensure that this pathogen is not being unknowingly distributed in existing or newly-released scion and rootstock budwood. * If these trees are not certified viroid-free prior to distribution. 27

32 Besides the obvious problems of propagation and increase that are associated with graft transmission, growers and nurseries should be aware of the following: Mechanical transmission: The high reported rates of mechanical transmission (up to 30% using seedlings and razor blades) are sufficient to justify special attention to transmission by pruning, cutting, or injection tools. Transmission can be prevented if tools are treated with a 15% bleach solution between trees. Root grafting: Movement of the viroid between trees may well be the result of root graft transmission especially in situations of close planting. Pollen transmission: Seeds from healthy trees pollinated with infected pollen can produce infected seedlings. A tree bearing pollen-infected fruit does not normally become infected itself. Seed transmission: Transmission through seed collected from symptomatic trees is low (less than 5%) but is reported to be high (80 to 100%) from symptomless carriers. Symptomless carriers: Healthy budwood topworked onto symptomless carriers is likely to develop symptoms. Seed from symptomless carriers is likely to give rise to infected budwood but symptomless seedlings. Nurse seedlings: These are used to establish clonal rootstock plants. It is unknown at this time what role, if any, nurse seedlings play in the ingress of sunblotch into the industry. There is currently no testing to ensure that seed sources are from healthy trees. The collection of nurse seed from an infected symptomless carrier with a high rate of seed transmission for routine nursery propagation could lead to outbreaks of sunblotch in new orchard plantings. 28

33 APPENDIX 2 INSECT MANAGEMENT 17 Consult a qualified Pest Control Advisor or University of California Farm Advisor before applying pesticides. Use the least harmful material available so as not to disrupt natural enemies and biological control. Avocado Thrips The major thrips pest attacking avocados California is the avocado thrips, Scirtothrips perseae Nakahara. Avocado thrips management costs are estimated to have reduced industry revenues by 12%, increased production costs by 4.5% Economic models indicate long-term losses to the California avocado industry to be around $4.45-$8.51 million per year. Costs to the California avocado industry related to avocado thrips management vary year-to-year depending on pest severity and fruit value. The main source of economic loss due to avocado thrips is scarring of immature fruit in spring by feeding activity of larval and adult thrips. Irregular brown scars on fruit surfaces become apparent as fruit grow and mature. Severe scarring can render the entire fruit surface brown with an alligator skin appearance. Fruit that are entirely scarred may continue to size but may be smaller than average at harvest, while the flesh remains normal. 17 Contributors: Mark Hoddle, Joseph Morse, Ben Faber, Pascal Oevering, Phil Phillips 29

34 Identification Avocado thrips larvae and adults are found primarily on the undersides of immature leaves and fruit. First instar larvae are pale white-yellow, while second instar larvae are much larger and bright yellow in color. Adult avocado thrips are straw yellow in color. The abdomens may appear greenish because of the chlorophyll extracted from plant material during feeding. The adults also have three bright red dots, or ocelli, between their eyes, which are light sensitive organs. Avocado thrips has six distinct life stages. Females lay eggs inside young leaves and fruit. Two larval stages subsequently develop and feed on young leaves and fruit. The two pupal stages are nonfeeding. Pupation occurs either in cracks or crevices on branches or in leaf duff below trees. Adults, which emerge from the pupal stage, feed on leaves and fruit, and, because they can fly, can disperse to adjacent trees to search for young leaves and fruit in which to lay eggs. Avocado thrips adult Avocado thrips life cycle Avocado thrips are readily distinguishable from another avocado pest, the greenhouse thrips, which are much larger and black in color. 30

35 Western flower thrips, a common native Californian thrips species, is yellowish-brown in color and is about 33% larger than avocado thrips. It is never found feeding on leaves and fruit, but is often found in avocado flowers feeding on pollen. Adult western flower thrips can be distinguished from adult avocado thrips based on size, obvious bristles on the tip of the abdomen which avocado thrips lack, and their association with avocado flowers. Field Ecology Avocado thrips larvae and adults can build to high densities over the fall through spring period on young leaves. When severe thrips feeding damage occurs, it can cause premature leaf drop. The main source of economic loss attributable to avocado thrips is scarring of immature fruit in spring by the feeding activity of larval and adult thrips. Elongated and irregular brown scars on fruit surfaces become apparent as young fruit elongates and matures. Orchards within 10 miles of the coast typically have a more severe avocado thrips problem than orchards further inland. The cool marine influence is thought to be conducive to avocado thrips population growth, while the hotter interior regions are too harsh for avocado thrips. Consequently avocado thrips densities decline in the field with the onset of hot summer weather, even when there is abundant foliage available for feeding and egg-laying. The influence of high temperatures on populations in orchards is not immediate. It appears that several consecutive days of high daily temperatures (i.e., maximum daily temperature must exceed 86ºF) and possibly low canopy humidity are needed to cause population declines. Thrips numbers rebound when mean weekly maximum temperatures decrease to within 68-76ºF, when there is abundant foliage for feeding and egg-laying, and when natural enemy activity is low. 31

36 Avocado Thrips and Fruit Scarring Female avocado thrips lay eggs into young fruit. Feeding on the fruit surface by emerged larvae can cause peel damage. Fruit are most susceptible to thrips damage when the fruit are inches in length. However, observations in the field on Hass indicate that fruit inches are most preferred by avocado thrips, possibly because fruit of this size have a reduced propensity to drop prematurely from trees and are still tender enough for egg-laying and larval feeding. Once fruit exceeds 2 inches in length, avocado thrips adults and larvae avoid these fruit and feed primarily on young leaves. Sampling for Avocado Thrips The most effective way to sample for avocado thrips larvae and adults is to use magnifying lenses to examine the undersides of leaves for the presence of thrips. Small fruit can be examined in a similar manner. Yellow sticky cards can also be a very useful tool for monitoring adult densities in orchards over time, for gauging directionality of flights within orchards, and for monitoring natural enemy species and their relative densities. Sticky cards should only be used for avocado thrips monitoring if the technician examining the cards is expert enough to separate avocado thrips from other yellow-colored thrips species that are also likely to be caught on the cards. It is advisable to have a qualified pest control advisor (PCA) monitor your thrips populations before and during periods of potential fruit damage. Biological Control of Avocado Thrips Several species of predacious insects eat avocado thrips in California avocado orchards. These natural enemies include green lacewing larvae, a predaceous thrips: Franklinothrips orizabensis, and predatory mites, in particular Euseius hibisci. Foreign exploration for avocado thrips natural enemies (predator thrips and parasitoids) in Mexico is ongoing. 32

37 Green lacewing larva Franklinothrips adult Inoculative releases of natural enemies of avocado thrips (green lacewing larvae and/or Franklinothrips adults) early in the season in anticipation of increasing avocado thrips populations are done by some growers. However, the efficacy of these releases has yet to be verified experimentally. Cultural Control of Avocado Thrips A novel method of controlling avocado thrips pupating in the soil beneath host trees (around 78% of second instar larvae drop from trees to pupate in the soil), using coarse composted organic yard waste, is presently under evaluation. Mulch is available from green-waste processing facilities. Freshly, properly-composted material will be devoid of avocado pests and diseases, as well as fruit rot organisms. A small field trial has demonstrated that 50% fewer thrips larvae emerged from mulch spread under avocado trees in comparison to non-mulched trees that had normal avocado leaf duff and branches under them. We speculate that composted mulch suppresses avocado thrips pupation because it harbors a more diverse fauna of natural enemies (including insect killing fungi, nematodes, and generalist arthropod predators) that opportunistically feed on microarthropods living in the mulch. This diverse fauna is somewhat lacking in the regular avocado leaf/branch duff under trees. Consequently, these generalist natural enemies attack avocado thrips larvae that fall from trees to pupate. 33

38 Before we can recommend mulches for avocado thrips control, this trial must be replicated in different orchards for longer time periods to determine whether or not: 1. mulch can provide orchard-wide suppression of avocado thrips; 2. reduction of thrips emergence is great enough to prevent economic damage to fruit; 3. the level of suppression seen is consistent year to year; and 4. how regularly mulch needs to be reapplied as it decomposes. Chemical Management of Avocado Thrips In developing a strategy for managing avocado thrips, growers should consider several interrelated factors including: 1. tree size and vigor (which may affect the amount and timing of leaf flushes which avocado thrips prefer); 2. past history of avocado thrips population dynamics and fruit scarring experienced in the grove and surrounding regions; 3. the amount of leaf flush and/or small fruit present; 4. whether or not these fruit are the major set or if additional fruit sets are expected; 5. avocado thrips levels and natural enemy levels; 6. grove topography; 7. spray equipment availability; and 8. the grower s tolerance for fruit scarring and interest in preserving avocado thrips pesticide susceptibility. One should also consider that the weather and the timing and amount of leaf flushes and avocado fruit sets can vary tremendously from year to year. Just because avocado thrips caused significant fruit scarring one year, or in a particular grove, does not mean that this or other nearby groves will have economic avocado thrips levels in subsequent years. 34

39 Many groves do not need to be treated for avocado thrips control and as a general principle, if practical (see comments on spray equipment availability below) it is best to withhold treatments as long as possible to maximize the impact of warm spring weather and natural enemies on avocado thrips levels. Under ideal circumstances, treatments should not be applied until it is clear that economic levels of avocado thrips are present during significant fruit set and that these levels are likely to cause economically significant damage. (i.e., one might withhold treatments on off-bloom fruit if hot weather is imminent, if natural enemy levels are high, or if one has a high tolerance for fruit scarring.) Because making decisions on the need for and timing of avocado thrips treatments can be difficult, we suggest that growers become as familiar as possible with avocado thrips and natural enemy biology, possible control options, and/or that they employ a knowledgeable pest control advisor to assist with scouting and decision-making. Each year and each grove situation can be different. The ability to make optimal pest management decisions is only developed through experience. There are currently three major options for chemical control of avocado thrips. These are listed below from least to most persistent control of avocado thrips. Read and follow pesticide labels for restrictions, warnings, and recommended rates. In particular, note label restrictions on the use of Success and Agri- Mek during bloom when bees are foraging. With three available insecticides for avocado thrips control, the development of avocado thrips resistance is a real concern and unnecessary treatments should be avoided. 1. Veratran D + Sugar/Molasses. This is a botanical pesticide made from the ground seeds of Schoenocaulon officinale, a lilylike plant. A 50-lb. bag of Veratran D contains 80% (40 lbs.) sugar as bait and 0.2% sabadilla alkaloids (0.1 lbs. or 45.4 grams). Up to an additional 10 lbs. sugar or 1.5 gallons of molasses should be added to the spray mix. 35

40 The liquid in the spray tank should be acidified to ph 4.5 prior to adding the Veratran D to the tank. Acidification helps to maximize treatment efficacy. Veratran D residues are not persistent on leaves and are reduced to 50% of the initial level approximately 4 days after treatment, resulting in perhaps 1-3 weeks of control depending on weather, application method, and thrips levels. (Since it is a bait, rain will tend to wash off the material and can render treatment ineffective). To avoid plugging of spray lines, screen size should be 20 mesh or larger and, because this material must be consumed by the thrips to be effective (it is a stomach poison with minimal contact activity), it is wise to withhold additives from a Veratran D treatment unless experience has shown that efficacy is not compromised. Because Veratran D is a stomach poison, it is relatively innocuous to most thrips natural enemies. In a grove in Ventura County that applied 6 Veratran D treatments over 2 years, an eleven-fold resistance of avocado thrips developed to this material. 2. Success 2 SC + Narrow Range 415 Spray Oil Success is in the macrocyclic lactone class of chemistry, is unstable in sunlight (most surface residues are degraded within a day), and exhibits translaminar activity (it moves into the upper cell layers of leaves or fruit where it is toxic to avocado thrips when they feed). Oil is required to move Success into leaves or fruit and should be added to the spray tank at a rate of.25-1%. Do not use acidifying buffering agents in tank mixes with Success. Success is relatively innocuous to natural enemies and treatments normally hold for 2-4 weeks. 3. Agri-Mek 0.15 EC + Narrow Range 415 Spray Oil Agri-Mek is also a macrocyclic lactone, is unstable in sunlight, exhibits translaminar activity, and must be used with oil. Thrips poisoned by Agri-Mek take 3-5 days to die and, thus, control can be somewhat slower than with faster acting insecticides. This material is quite persistent in leaves and treatments and can be effective for 6-10 weeks or more. Agri-Mek is also fairly innocuous to natural enemies. 36

41 Avocado Thrips Resistance Potential Avocado thrips have been shown to develop resistance to Veratran D. If Veratran D is being relied on for avocado thrips control, we suggest a maximum of 2-3 applications per year. Additionally, this material should be rotated with either Agri-Mek or Success to reduce the rate at which insecticide resistance will develop. Avocado thrips also have the potential to develop resistance to Agri-Mek and Success. Because Agri-Mek and Success are of similar chemistry, there is a concern that cross-resistance might appear (i.e., if thrips develop resistance to one material, they might also be resistant to the other). For these reasons, we suggest that growers apply only one treatment of Agri-Mek per year, one or two applications of Success per year (it is less persistent in leaves and fruit than is Agri-Mek), or one Agri-Mek and one Success treatment per year. Spray Application Methods Most avocado groves are on hillsides, making it difficult to apply pesticides other than by air. A problem, however, is that there are a limited number of companies that provide air treatments to avocados; thus, in years when the weather is warm and thrips levels are high, one can be caught in a spray queue. Even if treatment recommendations are written early, application may not occur until after appreciable scarring has occurred on fruit. For this reason, we suggest that growers consider the possibility of applying treatments using hand-held or ATV mounted ground spray equipment where grove topography makes this method possible. The advantage of such equipment is that sprays can be timed optimally and coverage can be good unless trees are extremely large. In regions where avocado thrips is a recurring problem, we suggest that growers in an area might consider pooling their resources to build or purchase hand-spray equipment, or consider contracting out to companies who might apply such treatments. 37

42 For long-term resistance management, it would be best to apply a single treatment shortly before thrips start scarring fruit (i.e., during late bloom if possible) using ground application and thorough spray coverage. Considering the Use of Prebloom Sprays Because of spray queue concerns, especially in regions where applications during bloom and in the presence of honey bees are restricted, some growers have experimented with prebloom Agri- Mek sprays. (Veratran D and Success are normally not sufficiently persistent to provide fruit set control when applied during the prebloom period.) If high avocado thrips populations (5 immature thrips per leaf or more) are present on foliage prior to bloom, and one does not have the option of using a ground spray, then such a strategy may be justified. However, avocado thrips populations often decline during the bloom period (depending to a good extent on the amount of tender leaf flush available), and often such prebloom treatments may not be needed. New chemicals for avocado thrips control are being tested, but at present few appear promising. All three of the materials presently available for avocado thrips control are quite selective (minimal impact on natural enemies and lack of disruption of other pest species). In addition, Agri-Mek provides remarkably persistent avocado thrips control. This, however, is a double-edged sword: control persistence is a plus but this persistence also contributes to the potential for resistance developing more quickly than if the material was less persistent. It is essential that growers and pest control advisors should consider pesticide resistance management when planning their avocado thrips management program. 38

43 Persea Mite 18 Persea Mite Identification Persea mites (Oligonychus perseae) feed in colonies beneath protective webbing, in nests that are formed along midribs and veins on the undersides of avocado leaves. Feeding damage from these mites produces circular yellow to dark brown necrotic spots. Persea mite populations typically begin building in mid-summer. These cause most damage to leaves by late summer when defoliation of leaves with heavy feeding damage commences. The closely related avocado brown mite (Oligonychus punicae) feeds on upper leaf surfaces. Feeding damage from these mites results in bronzing of upper leaf surfaces. The six-spotted mite (Eotetranychus sexmaculatus) is very similar in appearance to persea mite and also feeds on undersides of leaves. Six-spotted mites prefer to feed adjacent to the midrib and large lateral veins. Feeding damage from six-spotted mites produces purplish and irregular necrotic spotting. All three pest mites damage leaves by removing chlorophyll during feeding. Persea mite adults and nymphs Persea mite life cycle 18 Contributor: Mark Hoddle 39

44 Monitoring Persea Mite Populations The probability of leaf drop as a result of persea mite feeding increases greatly once % of the leaf surface is damaged. Generally, control measures need to be implemented before this level of damage is observed. An estimate of the number of mites infesting leaves and the percentage of leaves infested on trees can be made using a counting technique that records the number of motile mites infesting the half second vein (see diagram below). The average number of mites counted on 10 randomly selected leaves along this vein is multiplied by a correlation factor (= 12) to provide an estimate of the average number of mites per leaf. Some pest control advisors (PCAs) recommend spray treatments when sampling indicates there are persea mites per leaf. A field counting technique that records the number of motile persea mites infesting the half second vein on sampled avocado leaves. The average number of mites along this vein on 10 randomly selected leaves is multiplied by a correlation factor (12) to provide an estimate of the average number of mites per leaf (courtesy of Dave Machlitt). 40

45 Population Cycles High density persea mite populations typically undergo rapid crashes towards the end of summer. Three mechanisms have been proposed to account for this: 1. Natural enemies, in particular, the naturally occurring predatory mite, Euseius hibisci, build up over the summer and control persea mite late in the summer. 2. Heat waves (several consecutive days with temperatures exceeding 100 o F accompanied with low humidity < 50%) cause mortality of immature and adult mites. 3. A lack of healthy undamaged leaves to be used as food or nest sites contributes to population declines. Field work suggests that heat waves and lack of food are major contributors to mite population crashes, rather than natural enemies. Long-term monitoring studies have shown that persea mite is not a persistent problem in orchards more than 20 miles inland, probably because consistently high summer temperatures are unfavorable for mite population growth. Additionally, studies have shown that persea mite ballooning (i.e., aerial migration by mites using silk strands that act as sails or balloons) from avocados occurs as populations increase. This is correlated with increasing competition (many mites on leaves) and a deteriorating food supply (numerous necrotic spots on leaves). It is probable that all three factors, either alone or in some combination, contribute to the rapid declines of high density persea mite populations at the end of summer. Controlling Persea Mite on Avocados Predatory Mites: Based on the results of field trials, the commercially available predatory mites with the most potential for controlling persea mite are Galendromus helveolus and Neoseiulus californicus. 41

46 The use of N. californicus is recommended because it costs less than G. helveolus from commercial insectories and because leaves suffer less persea mite feeding damage when N. californicus is used. N. californicus can be released manually into the grove. Experiments have shown that, when manually releasing N. californicus using small paper cups attached to branches on 15 foot avocado trees, a minimum of 2000 predators per tree is required to control persea mite. Releasing fewer than 2000 N. californicus per tree by hand will probably not result in successful biological control of persea mite. (Effective releases of 2000 N. californicus per tree can be achieved by either releasing 1000 N. californicus twice or 2000 N. californicus once.) Persea mite feeding damage. Predator releases should begin when 50% of sampled leaves have one or more motile persea mites (not eggs) per leaf. If releases are made too early (i.e., at 25% leaf infestation), there is not enough food for predators to establish. If releases are made too late (i.e., at 95% leaf infestation), persea mite numbers are too high for predators to control and significant leaf damage will result. A second release of predators can be made when 75% of leaves sampled have more than one motile persea mite. To estimate the percentage of leaves infested with persea mite, choose 50 leaves at random from several trees and multiply the total number of leaves with one or more motile persea mites by two (e.g., 15 infested leaves out of 50 is 30% leaf infestation). 42

47 Neoseiulus californicus does not appear to over-winter in large numbers in California avocado orchards; therefore, predator releases need to be made each year. Furthermore, field studies suggest that N. californicus will not disperse from central release points in orchards and needs to be released onto each tree to be effective. At this time, it is believed that the release of predator mites for persea mite control is not economically competitive with the use of pesticides. (Some PCAs have reported good control of persea mite by releasing N. californicus or G. helveolus at a rate of 5000 per acre.) PCAs release predator mites by spraying infested leaves with water and then sprinkling a small amount of corn grits with predators onto the dampened leaf. The water traps the grits with the predators. As the water dries, the predators free themselves and commence searching for prey. Every tree in an infested block is treated in this manner. A list of suppliers of predatory mites in California is available at your local University of California Cooperative Extension office or at: Insecticides: Legal pesticide control options for persea mite are limited. Narrow range 415 petroleum oil can be used to control persea mite populations. In some instances application of NR 415 oil may lead to persea mite resurgence, that is, mite populations rebound to higher densities than those seen at the time of spraying. Resurgence occurs because generalist natural enemies (e.g., predatory thrips, flies, and mites) that were providing some suppression of persea mites are eliminated from trees. Abamectin (Agri-Mek) mixed with NR 415 oil applied for avocado thrips control in late spring or early summer has been demonstrated in several field evaluations to have a strong and prolonged impact on persea mite populations. It must be noted that, at the time of this writing, Agri-Mek has not been approved for use solely as a mite control agent. 43

48 Help with Treatment Decisions: Control decisions for persea mite should be based on population monitoring of the pest and its natural enemies. Consult with a Pest Control Advisor (PCA) or UC Farm Advisor for recommendations specific to your situation. Cultivar Susceptibility and Alternative Host Plants Avocado cultivars vary in their susceptibility to persea mite feeding damage. By calculating the average percentage of leaf area damaged by mite feeding, cultivars have been ranked from least susceptible to most susceptible as follows: Fuerte (average leaf area damaged by feeding persea mites is 13.3%) <Lamb Hass (16.9%) = Reed (16.9%) <Esther (29.7%) <Pinkerton (30.2%) <Gwen (37.4%) <Hass (38.4%). The mechanism by which Fuerte and Lamb Hass reduce feeding damage is unknown, but could be related leaf chemistry or morphology, which may reduce mite survivorship or reproduction rates, or both. In addition to avocados, persea mite can develop on a wide range of fruit, ornamental, and weed plants, such as Thompson and Flame seedless grapes (Vitus sf), apricots, peaches, plums and nectarines (all Prunus spp.), persimmons (Disopyrus spp.), milkweed (Asclepias fuscicularis), sow thistle (Sonchus sp.), lamb s quarters (Chenopodium album), sumac (Rhus sp.), carob (Ceratonia siliqua), camphor (Camphora officinalis), roses (Rosa spp.), acacias (Acacia spp.), annatto (Bixa orellana), willows (Salix spp.), and bamboo (Bambusa spp.). Good grove sanitation practices (i.e., elimination of favored weed species) and removal of alternate host plants (i.e., ornamental plants and non-commercial fruit trees in orchards) that act as persea mite reservoirs are useful cultural control practices that should be employed in an integrated persea mite management program. More information can be found at: 44

49 Worm Pests Omnivorous looper, avocado amorbia (Amorbia cuneana) and, very occasionally, orange tortrix worms can cause fruit damage in California groves. An ideal environment for these worms is densely canopied trees in orchards where large trees form a continuous canopy of foliage. Pruning individual trees to open the canopy to light or removal of every other tree in a thinning pattern can reduce the severity of an avocado worm infestation. Omnivorous Looper 19 Omnivorous loopers are common in many avocado groves, generally in low numbers, unless there has been an upset caused by broad-spectrum chemicals used for the control of other pests such as greenhouse thrips. The name "looper" comes from the crawling or looping movement of the larva as it extends its forelegs outward and then draws up the rear legs, thereby creating a loop. All stages of this insect may be found in low numbers in winter. As temperatures increase in spring, populations increase. Adult moths live 2 to 3 weeks. Females lay 200 to 300 pale green, barrel-shaped eggs in clusters of 3 to 80 on the undersides of leaves. Newly hatched larvae are pale yellow and about 0.06 inches long. Full-grown larvae are 2 to 2.5 inches long and 0.25 inches wide. The entire larval period averages 6 weeks. Larvae may be found singly on leaf edges or on succulent twigs (especially terminal growth shoots), or in groups or singly between two leaves that are tied together with silk. As with adult moths, larvae are most active at night. It is uncommon to have both omnivorous looper and amorbia larvae (see below) on the tree at the same time, although their generations do overlap (omnivorous looper has three to four generations per year and amorbia has four to fve). One way of distinguishing the two species is that omnivorous looper larvae drop on a silken thread from leaves when disturbed while amorbia larvae do not. 19 Contributors: Ben Faber, Phil Phillips, J. Blair Bailey 45

50 Omnivorous looper larva (above) and adult (below). Photos by Max Badgley Regents, University of California. Pupae are 1 to 1.25 inches long and are usually found between two webbed leaves, or inside leaves that were rolled by mature larvae. When adult moths emerge, they have a wingspan of about 1.75 to 2 inches. Adult moths are nocturnal. During the day they hide on the undersides of leaves or in shady areas on the bark. Moths are strongly attracted to security lights or other bright light sources. Larval infestations are often concentrated near trees adjacent to light sources. Depending upon temperatures and humidity, their entire life cycle takes 9 to 11 weeks. There are five generations per year in the warmer southern parts of California. Looper Damage Larval looper worms may damage leaves and fruit. Fruit damage can be caused by young or old larvae. If young fruit is fed on, its shape becomes distorted. When larger fruit are fed on, the fruit surface is scarred, which may provide an entry point for rots and also cause fruit to be downgraded. 46

51 Monitoring and Control Monitor larvae throughout spring and summer, particularly from May through July, every 7 to 10 days. Pheromone traps are commercially available and are used primarily to identify periods of peak flight activity. Shortly after peak flights, begin looking for larvae in leaf rolls and in areas where fruit touch each other, mainly on the south and east quadrants of trees. Also check for evidence of parasitism. If 15 healthy larvae are found per hour of search, treatment may be necessary, depending on whether or not the orchard has a history of egg and larval parasite activity. When high numbers of larvae are found, watch for evidence of granulosis virus disease. When this disease is present, the worm populations may decline rapidly and other treatments may not be necessary. Diseased larvae cease feeding, become lethargic, eventually liquefy and then dry up in their nests. Several tiny wasps parasitize eggs and larvae of omnivorous looper, including the Trichogramma platneri wasp, which is commercially available for purchase and release. The pupal stage of the looper is often also parasitized by a tachinid fly about the size of the common housefly. The tiny, dark brown pupal cases of the fly are often found alongside the larger looper pupal case. Spiders also feed on loopers and are most abundant in groves that have not been sprayed with a pesticide or subjected to a freeze. If a spray treatment is deemed necessary, Bacillus thuringiensis (Bt) sprays are an organically accepted and effective control measure and are the least disruptive to beneficial organisms in the grove. Amorbia 20 Most avocado groves in California have populations of amorbia. Occasionally, amorbia populations increase dramatically and can cause severe fruit damage. Although the insect appears to prefer avocado as a host plant, it is also found in citrus. 20 Contributors: Ben Faber, Phil Phillips, J. Blair Bailey 47

52 Amorbia larva (left) and adult (right). Photos by Max Badgley Regents, University of California. Adult female moths lay light green, oval-shaped eggs, overlapping and shingle-like, in flat masses of 5 to 100. Eggs are generally laid on upper leaf surfaces close to the midrib. As larvae develop within eggs, the egg mass darkens, signaling that larvae will soon emerge, usually 13 to 15 days from the time eggs are laid. Hatched egg masses appear as whitish patches on leaves. Newly hatched larvae are yellowish green and gradually turn darker green as they reach maturity. Amorbia larvae roll and tie leaves together with silken web. This forms a shelter or nest in which the larva feeds on leaves and fruit. This nest provides the larva with protection from most pesticide applications. Sometimes, larvae spin silk between fruits that touch each other. If disturbed, larvae wiggle violently and fall to the ground. As the larvae develop, they go through five stages (instars), each larger than the previous stage. Full-grown larvae are from 0.75 inches to slightly over 1 inch long. 48

53 Larvae pupate in leaf rolls and form pale green pupae that are from 0.5 to 0.75 inches long. Pupae gradually turn tan and at maturity become brown. The pupal stage lasts about 17 days before adult moths emerge. Adult moths are bell shaped and have a wingspan of about 1 inch (2.5 cm). Though considerable color variation occurs with both sexes, the forewings of a typical female are rusty tan, while those of the slightly smaller male are tan, with a triangular dark mark midway on the outer margin of the wings. Adults are active only at night. Female moths lay 400 to 500 eggs during 2 to 3 weeks. Amorbia Damage Mature avocado trees can tolerate considerable leaf damage by amorbia larvae without severe effects on tree growth or fruit yield. Fruit damage occurs where larvae make web on leaves against fruit, or where webs are made between touching fruit. In these protected sites larvae feed on fruit skin and cause scarring, which may cause downgrading. White sugary exudates are often seen near feeding damage. Monitoring and Control Beneficial parasites play a major role in keeping amorbia populations below economically damaging levels in most California avocado groves. The egg, larval, and pupal stages of amorbia are generally heavily parasitized by a variety of beneficial insects. One of the most effective parasites of amorbia eggs is the tiny wasp, Trichogramma platneri. Amorbia egg masses that appear black have probably been parasitized by this beneficial wasp. These wasps are commercially available for release in orchards. A tachinid fly, which is similar in appearance to the common housefly, as well as several parasitic wasps, attack the amorbia larvae. Small brown pupal cases of tachinid flies are often found near the larger parasitized amorbia pupal cases. A naturally occurring nuclear polyhedrosis virus can also control larvae when larval populations are high. 49

54 Monitor larvae in late spring by looking for webbing and leaf rolls in young foliage and feeding damage on young and mature fruit located on the outside of the canopy. There are no established thresholds for spray control. However, if a spray treatment is necessary, Bacillus thuringiensis (Bt) sprays are recommended and are an organically accepted and effective control measure. Bt sprays are the least disruptive to beneficial organisms in the grove. Spraying with malathion, methomyl, or carbaryl often leads to outbreaks of other pests and is not recommended. Monitor parasites several times to determine whether or not their populations are increasing. If they are, then amorbia populations will likely decrease. 50

55 APPENDIX 3 VERTEBRATE PEST AND SNAIL CONTROL 21 Rats Besides damaging fruit, rats can transmit diseases to humans and livestock. Since rats are most active at night, you probably won t see them damaging your fruit. However, signs of rat damage will become more noticeable as the picking season for a particular variety approaches. The most obvious evidence of damage is fruit that has been chewed, which packers will cull at the packinghouse. Roof rats are especially fond of avocados and often eat fruit that is still on the tree. Other signs of a rat problem include burrows under compost piles or along building foundations, rat nests behind storage boxes, and droppings near pet food dishes. Identification In order to place traps where they will be most effective, it is important to identify which species of rat is causing the problem. In California, the most troublesome rats are roof rats (Rattus rattus), sometimes called black rats, and Norway rats (Rattus norvegicus), sometimes called brown or sewer rats. Adult roof rat. Photo by Jack Kelly Clark Regents, University of California. 21 All photos in Appendix Regents, University of California and are from the following online publication from the University of California s Statewide IPM Program: Salmon, T. P and P. Gorenzel Pest Notes: California Ground Squirrels. UC ANR publication 7438, available at the University of California UC IPM Program web site: 51

56 Roof rats are sleek and agile. The roof rat s belly is gray to white in color, and its black tail is longer than its head and body combined. The roof rat has a pointed muzzle, and its ears are long enough to reach its eyes if folded over. Roof rats are very agile climbers and usually live and nest in shrubs, trees, and dense vegetation such as ivy. They can often be seen at night running along overhead utility lines or fence tops. Norway rats are stocky and slightly larger than roof rats. The Norway rat s belly is mostly grayish in color, its muzzle is blunt, its ears are shorter than the roof rat s ears, and its tail is dark above, pale below, and shorter than its body. Norway rats dig burrows along building foundations, beneath rubbish or woodpiles, and in moist areas in and around gardens and fields. Adult Norway rat. Photo by Jack Kelly Clark Regents, University of California. Control Continuous sanitation is fundamental to rat control. Without proper sanitation, the benefits of other measures will be lost and rats will return quickly. Clear brush and remove piles of pruned wood frequently from, in, or near the orchard to reduce natural nesting areas. Thin or remove climbing hedges (such as ivy, star jasmine, and honeysuckle) from along fences and buildings. Keep overhanging tree limbs trimmed so that they are more than 3 feet from buildings. Store pipes, lumber, firewood, crates, boxes, and equipment off the ground. 52

57 Store pet food in rodent-proof containers and do not leave leftover food in outside pet dishes. Make sure that all garbage containers are tightly covered. Rodent proofing measures should be taken in all buildings adjacent to groves. The most successful and long lasting form of rat control in buildings is to seal them out. Use coarse steel wool, wire screen, and lightweight sheet metal for plugging gaps and holes. Less sturdy materials, such as plastic sheeting, wood, and caulking, can be gnawed away. Seal all cracks and openings in building foundations. To exclude both rats and house mice, seal any openings for water pipes, electric wires, sewer pipes, drain spouts, and vents that are larger than 1/4 inch. Make sure windows, screens, and exterior doors fit tightly. For roof rats, be sure that all entry points in the roof are sealed. If roof rats are traveling on overhead utility wires, contact a pest control professional or the utility company for information on how to prevent this. Trapping is the safest and most effective method of controlling rats in and around buildings. Use simple wooden snap traps or the newer rat traps with large plastic treadles. Bait the traps and place them about 10 to 20 feet apart. Since rats are suspicious of new objects in their habitat, leave traps baited but unset until the bait has been taken at least once. For Norway rats, set traps close to walls, behind objects, in dark corners, and in places where rat signs, such as gnawing and droppings, have been seen. For roof rats, place traps where rats may come down from their nests to find food, such as on ledges, shelves, branches, fences, pipes, or overhead beams. Fasten traps with screws or wire. 53

58 Baiting is recommended for use in avocado groves. There are several good rodent pesticides available through your pesticide dealer. Bait blocks should be placed in tamper-resistant bait stations where children, dogs, and other animals will not be able to reach them. Commercial bait stations are available in a variety of sizes and shapes. For Norway rats, place bait stations near rodent burrows or suspected nest sites, against walls, or along travel routes. For roof rats, place bait in elevated locations, such as in the crotch of a tree, on top of a fence, or high in a vine. One treatment that works well against rats in orchards is moisture-resistant paraffin blocks impregnated with anticoagulant poison that can be nailed into the trees above the reach of other animals. These require multiple feedings to be effective, so make sure there is a continuous supply of bait until feeding stops. It often takes five days or more of feeding for rats to succumb to this treatment. Bury dead rats or place them in sealed plastic bags and dispose of them in the trash. Do not touch dead rats with bare hands and wash thoroughly after handling traps. Squirrels Ground squirrels can damage avocado trees by gnawing bark, girdling trunks, eating twigs and leaves, and burrowing around roots. They also gnaw on plastic sprinkler heads and irrigation lines. Ground squirrels can transmit bubonic plague to humans through fleas. If you find unusual numbers of squirrels or other rodents dead for no apparent reason, notify public health officials. Do not handle dead squirrels under these circumstances. 54

59 Identification The California ground squirrel, Spermophilus beecheyi, is easy to identify because it forages above ground near its burrow, mainly from midmorning through late afternoon. The ground squirrel is 9 to 11 inches in length with a semi-bushy tail and brownish gray fur speckled with offwhite along the back. The sides of the head and shoulders are light gray to whitish. Although ground squirrels sometimes climb trees, they always return to their burrows when frightened. (Tree squirrels do not threaten avocado trees. They are similar in appearance to ground squirrels, but will climb a tree or tall structure when frightened and will never use a burrow. Control California ground squirrel. Photo by Jack Kelly Clark Regents, University of California. Sanitation, such as removing brush piles and debris, makes an area less desirable to ground squirrels. To prevent them from reinvading, destroy vacant burrows by deep ripping them to a depth of at least 20 inches using a tractor and ripping bar(s). Do not perform this operation in areas where avocado roots exist. Simply filling in the burrows with soil does not prevent reinvasion. Baiting with anticoagulant baits, such as Diphacin-treated grain, is effective in summer and fall because squirrels primarily feed on seeds during this period. These baits can be purchased from the county agricultural commissioner s office or from a pesticide dealer. Unless the label specifies otherwise, place bait in bait boxes with openings about 3 inches wide so that only squirrels can enter. This will prevent pets, children, and non-target animals from being poisoned. 55

60 Many anticoagulants (including Diphacin) must be consumed for five or more days in order to be effective, and it takes several days for squirrels to become accustomed to the bait boxes before they will enter them. This means that it may be 2 to 4 weeks before the squirrel population is wiped out. During this period you must provide a constant supply of fresh, treated grain and remove leftover grain at the end of each day. Fumigation is most effective in spring when soil is moist, which helps seal gasses in the burrow system. Fumigating in the spring also prevents squirrels from reproducing. Do not fumigate in summer when soil is dry. USDA gas cartridges can be purchased from many agricultural commissioners offices. Trapping is practical when the squirrel population is low to moderate. Live-catch traps are not recommended due to strict government regulations regarding how and where the animals can be re-released. There are several types of traps that kill ground squirrels, such as box traps and Conibear traps. Box traps should be placed on the ground near squirrel burrows or runways and baited with walnuts, almonds, oats, barley, or melon rinds. Bait the traps but do not set them for several days so that the squirrels will become accustomed to them. After the squirrels are used to taking the bait, rebait and set the traps. Place the bait well behind the trigger or tied to it. Box trap. Adapted from Salmon, T. P., and R. E. Lickliter Wildlife Pest Control around Gardens and Homes. Oakland: Univ. Calif. Agric. Nat. Res. Publ

61 Conibear traps are set over the entrance of a ground squirrel burrow and secured with a stake so that the squirrel must pass through the trap to enter or leave. The wire trigger is usually left unbaited. If necessary, partially fill in the edges of the burrow entrance to prevent the squirrel from going around the trap. Inspect traps daily and remove dead carcasses. Cover your hands and arms with a plastic bag before handling dead squirrels. After removing the squirrel from the trap, hold it with one hand and turn the bag inside out while slipping it off your hand and arm. Brown Garden Snails The Conibear trap is secured with a stake and set over the burrow entrance of a ground squirrel, Spermophilus beecheyi. Photo by Jack Kelly Clark Regents, University of California. Brown garden snail.. Photo by Jack Kelly Clark Regents, University of California. Predaceous decollate snail.. Photo by Jack Kelly Clark Regents, University of California. Brown garden snails (Helix aspersa) will scar immature fruit, causing it to be downgraded at the packinghouse. They will also attack leaves of young trees and small grafts to the extent that the damaged plant is set back or the graft killed. While chemicals such as iron phosphate and metaldahyde can do the job at minimal cost, biological control with decollate snails (Rumina decollate) is preferred. Decollates are small snail-eating snails that provide good control of brown garden snails. 57

62 APPENDIX 4 HARVESTING AND FIELD HANDLING When harvesting and handling fruit, it is essential to avoid field heat in fruit, damage to fruit, handling wet fruit at harvest, and holding fruit too long after harvest. When harvesting and handling California avocados, it is well worth remembering that: 1. Fruit is alive and breathing. Fruit respire at very high rates. When confined in a bin, this can significantly raise the temperature of the fruit, especially during warm harvest-time temperatures. Hosing or misting the fruit to cool it during very warm temperatures should be the last resort for temperature control because wetting fruit may increase fruit rot later at retail. 2. Fruit are very sensitive to ethylene, which will trigger and promote faster ripening if allowed to accumulate during storage. Fruit produce ethylene themselves as they ripen. Mechanically damaged fruit may cause the automatic production of ethylene in nearby fruit, resulting in uneven ripening. 3. Fruit transpire and can lose significant quantities of water after harvesting, with a consequent loss of quality. Water loss can also aggravate the symptoms of mechanical damage and cold or warm temperature injury. 4. Fruit are very sensitive to temperature. Fruit picked at higher temperatures (> 90 F) rather than at lower temperatures (< 70 F) will: Lose up to 10 % more weight Respire at a much higher rate and accumulate heat in bins Take significantly longer to cool At lower the temperatures, rates of fruit respiration are lower. However, excessively low temperatures can also induce chilling injury. 58

63 Most quality problems occur when harvest and hauling temperatures are too high. This is because the fruit may ripen too quickly, not ripen at all, or develop off flavors. Avoid harvesting during hot weather (above 90 F) if you can. When the maximum temperature forecast for the day exceeds 90 F, hang a thermometer nearby in a shaded area of the orchard and monitor temperature during picking. Also, it is essential to maintain moderate bin temperatures during storage and during hauling to the packinghouse in order to slow down respiration and to prevent water loss, abnormal ripening, and fruit quality loss. 5. Fruit are sensitive to invasive organisms (rots) under certain conditions. There are two kinds of rots and several different fungi that can cause them. With stem-end rots the fungus enters through the cut stem. With body rots, the fungus enters through the side of the fruit, mainly through lenticels (pores on the fruit s surface that allow it to breathe). Lenticels tend to be located on the bumps on the peel. This location exposes the pores to physical contact and mechanical damage. When the fruit are wet, the lenticels are turgid and are very susceptible to damage through contact. The damaged lenticel cells die off during storage, allowing the rot fungi to grow and develop into a rot. Fruit are thought to be infected with these rots by water-borne spores, which exist in groves throughout the growing season. The source of these spores (inoculum) is found within the canopy, on the orchard floor, in surrounding brush, and in dirty bins. Hydro-cooling the fruit with a chlorine solution may reduce spores on fruit surfaces and subsequent rots. Two factors which greatly increase the risk of fruit developing commercially unacceptable levels of rots are: Handling wet fruit at harvest and Holding fruit too long after harvest. 59

64 Fruit harvested for up to 2 weeks after 2-3 days of significant rainfall is thought to carry a higher risk of fungal infection and should be handled accordingly. Stem-end rot (above) and body rots and bruising of Hass fruit (below). 60

65 APPENDIX 5 HYGIENE AND FOOD SAFETY 22 Foodborne Illness: Why Should We Care? As an industry we have been blessed with relatively few foodborne illness scares compared to some other fresh produce industries. However, pressure from outside the avocado industry has made food safety a higher priority than ever before. In response to consumer demands, some food retailers are addressing food safety by requiring farms that supply produce to obtain thirdparty inspections and certification of Good Agricultural Practices. Every year, foodborne illnesses in the USA cause an estimated: 76 million cases of sickness 325,000 people to be hospitalized 5,200 deaths, and Economic losses between $10 billion and $83 billion. Foodborne illness outbreaks can result in devastating financial losses. The strawberry industry lost an estimated $50 million in 1996 after mistakenly being identified as the source of pathogens (illness-causing organisms) in an outbreak. Illness outbreaks work against promotional campaigns and could result in unwanted legislation or regulation. Identifying all potential sources of pathogen contamination in our Industry will help prevent public relations and financial disasters in the future. The Key to Preventing Foodborne Illnesses is Preventing Contamination. Preliminary studies of apples and strawberries indicate that, once fruit is contaminated, pathogens are difficult to remove. Although we cannot eliminate all potential food safety hazards, 22 Contributors: Mike Villaneva, Mary Lu Arpaia 61

66 we can significantly reduce the risks by keeping contaminants off fruit. When and How Does Contamination Occur? Microbial contamination can occur in the grove during pre-harvest and harvest activities from contact with contaminated soils, fertilizers, water, workers, and growing and harvesting equipment. How Can Contamination Be Prevented? Microbial outbreaks of foodborne illness associated with fresh fruits and vegetables can be the result of contamination by fecal material. Growers should place a high priority on minimizing the potential for direct or indirect contact between fecal material and avocados. Examine your specific growing environment to identify other obvious sources of contamination. Keep wildlife and pets out of the production area as much as possible. Control rodents and birds in packinghouses and storage areas and keep dogs and other pets out of groves. Instruct workers not to pick fruit with obvious bird droppings on the surface. 1. Prevent fruit from direct contact with the ground. Fruit that has had ground contact holds the greatest potential for contamination. This problem can be reduced or eliminated by laying fruit on tarps before transporting it to bins. These tarps must be sterilized or replaced frequently. 2. Prevent contact with contaminated water. 23 Agricultural water can become contaminated, directly or indirectly, by improperly managed human or animal waste and may in turn contaminate fruit. Test water quarterly for fecal coliforms and keep records of all water test results. If fecal coliforms are detected 23 See Worksheet 6, Water Worksheet 62

67 in surface water, filtering the water or using settling ponds can reduce the count. Fecal coliforms in well water can be reduced with chemical treatments. Maintain a constant level of chlorine ( ppm) and a ph level of Be conscious of water temperature. While a higher water temperature kills pathogens more quickly, it also results in a rapid loss of chlorine due to gas formation. Use potable (drinking) water for pesticide sprays. 24 When potable water isn t available, test water quality and keep records. Work with local watershed committees and upstream neighbors on management goals. Ensure that fruit on the trees does not contact irrigation water to minimize the risk of crop contamination. 3. Prevent contamination from fertilizers. Manure and biosolids can be effective and safe fertilizers. However, untreated or improperly treated manure or biosolids that enter surface or ground waters through runoff may contain dangerous pathogens that could contaminate fruit. To minimize this risk, use properly composted manure. 4. Prevent contamination from workers. Field workers can unintentionally contaminate fresh produce, water supplies and other workers, and transmit foodborne illnesses if they do not follow good hygiene principles. Effective training and prevention result in better informed employees and in safer produce. 25 Anyone suffering from an infectious disease, ill health accompanied by diarrhea, open lesions (including boils, sores and infected wounds), or other ailments should be prevented from having any contact with fruit. 24 See Worksheet 7, Drinking Water Checklist 25 See Worksheet 8, Workers Training Documentation, and Worksheet 9, Employee Training Documentation 63

68 Teach and enforce proper handwashing techniques and encourage supervisors to set a good example. Educate workers on the importance of restroom use and proper handwashing. All workers should wash their hands after using the restroom, before starting or returning to work, and before and after eating or smoking. Provide properly located toilet and handwashing facilities for all orchard workers and ensure they are adequately stocked with toilet paper, soap, clean water, sanitary handdrying devices (such as disposable paper towels), and a waste container. Clean all toilets, sinks, and handwashing stations on a regular schedule. Water storage containers should routinely be emptied and thoroughly cleaned, sanitized and refilled with potable water. Document the above. 5. Ensure safe management and disposal of waste from toilet facilities. Improper disposal could lead to water, soil, animal, crop, or worker contamination. Use caution when servicing portable toilets. Toilet wastewater can contaminate produce if the wastewater drains into a field. Dispose of wastes through a municipal sewage system, a sub-surface septic tank system, or a properly constructed 64