Part 3: Pests and diseases of grapes. Introduction Vineyard pests Fungal infections The natural balance Competitors...

Transcription

1 Grape production Part 3: Pests and diseases of grapes Introduction... 2 Vineyard pests... 3 A grape epidemic - phylloxera...3 Fungal infections... 8 Black spot...9 Downy mildew...10 Powdery mildew...12 Fungicides...13 The natural balance The farm community...15 Mites, friend or foe?...17 Insect pests...20 Competitors Chemical control - herbicides...23 Organic weed control...27 Plant associations...30 Additional resources Suggested answers Exercises Part Part 3: Pests and diseases of grapes 1

2 Introduction Introduction In this part, you will be focussing on a number of different organisms that interfere with grape production - weeds, insect pests and fungi. These pests can damage the leaves, roots and fruit of a plant. Pest damage results in reduced yields, quality and financial returns. The management of pests in a vineyard is important to ensure the best quality vintage (harvest) possible. There are many ways this can be done including integrated pest management (IPM). An understanding of the life cycle of an organism, including the relationship to its host, helps to devise ways to manage populations. Every pest control program has its advantages and disadvantages in the short and the long term. An important problem you will be examining is resistance to chemicals. Netting is placed over vines in this vineyard in the Berry area to reduce damage to grapes by birds. (Photograph: Julie Robinson) This part contributes towards an understanding of Outcomes H1.1 and H2.1 from the Agriculture Stage 6 HSC Course. The syllabus can be found on the Board of Studies, NSW website at 2 Grape production

3 Vineyard pests Vineyard pests Market demand for high quality grape products means that pests must be controlled effectively. Damaged grapes mean lower returns, particularly in the table grape market. The term pests in this module refers to: disease-causing organisms, for example bacteria, viruses, nematodes, fungi insect pests, for example light brown apple moth, Rutherglen bug arachnids, for example blister mites, bud mites larger pests, for example rabbits, snails, birds. The grapevines first introduced into Australia were free from most diseases. Around the turn of the last century there was a lot of movement of vine material (mainly cuttings) around the globe. With these came the spread of vine pests. Fungi, viruses and insects spread from North America to Europe and then to Australia. The most devastating of the insect pests that entered the country in this way is phylloxera. A grape epidemic phylloxera Phylloxera is a tiny insect (like an aphid) that is extremely destructive, destroying vineyards all over the world. They feed on the roots, weakening vines and making them more susceptible to disease. By 1920 phylloxera had spread from North America to most of the major grape growing countries of the world. Source: Robinson J. (1986). Vines Grapes and Wines. Mitchell Beazley Publications. London. England. Part 3: Pests and diseases of grapes 3

4 Portugal, South Africa, New Zealand, France, Spain, the United States and Australia are major grapegrowing countries affected by outbreaks of phylloxera. Phylloxera was first detected in Australia in the Geelong area in The pest quickly spread throughout much of eastern Australia. Vines were uprooted in an effort to stop the spread of this insect pest. Rutherglen s vineyard area was reduced to a quarter of its size as a result! Brisbane 1902 Bendigo 1893 Geelong 1877 Sydney 1902 Rutherglen 1899 Heathcote 1899 The spread of phylloxera throughout Australia. The life and times of phylloxera A study of the life cycle of phylloxera has lead to more effective control measures. The life of phylloxera is complicated by the type of vine. There are several species of vines used in commercial grape production. Vitus vinifera is native to Europe and Central Asia. It is known as the European vine. There are a number of vine species native to America, for example, Vitus labrusca. This species, native to North America, was suspected of harbouring phylloxera which then hitchhiked into Europe and Australia. Some American species are resistant to phylloxera; the European species is not. There are three main stages in the life cycle of phylloxera on Vitus vinifera: the wingless adult; eggs; and nymphs. These occur on the host s roots. Other stages exist on different vine species. Nymphs are brown in colour and much smaller than the adults which are green, brown or orange and around 1 mm long. Phylloxera survive the winter (overwinter) as nymphs sheltering under the bark of the older roots. During the growing season, nymphs develop into wingless adults which can lay up to 200 eggs. This cycle can occur 4 Grape production

5 several times, producing numerous pests. During spring, nymphs feed on the younger roots, weakening the vine. Root galls develop which stop the roots from growing. Older vines with more extensive root systems last longer when infected. Vitus vinifera (the host) nymphs overwinter (winter) nymphs infest other vine roots nymphs feed (spring) adult several generations during a season nymph eggs A simplified life cycle of phylloxera in the soil around European vines. Phylloxera can spread to nearby vines in various ways. Nymphs can travel through cracks in the soil. They cannot move through coarse sandy soil, preferring heavy clay soils. Nymphs can also travel on the surface of the ground. They can be blown onto other plants by the wind. Phylloxera can also reach nearby vineyards by the movement of machinery or equipment. Part 3: Pests and diseases of grapes 5

6 1 Describe the features of a vineyard that can be badly affected by phylloxera. 2 Describe the features of a vineyard least threatened by phylloxera. _ Check your answers. Control of phylloxera Quarantine regulations to prevent the introduction of grape phylloxera into areas free of phylloxera. Scanned from Are you alert to quarantine? (1990). Department of Primary Industries and Energy. Australian Quarantine and Inspection Service. Canberra. Australia. Commonwealth of Australia copyright reproduced by permission. 6 Grape production

7 Most grapevines in Australia are varieties of the European grapevine Vitus vinifera which is susceptible to attack by phylloxera. In areas where phylloxera is present, vines are often grafted onto resistant rootstocks (from American grapevine species). Establishing a vineyard with resistant rootstocks greatly increases the cost but reduces the risk. Quarantine regulations, in force since 1899, have contained the pest to the original outbreak areas. The movement of vine material is restricted in areas where phylloxera is still active, for example, in the Sydney region. An understanding of how the pest spreads is essential to its control. 1 Quarantine areas are often signposted with rules. What regulations might be on a sign when you were: a) entering the Hunter region b) entering the Corowa district. 2 How do quarantine restrictions help to control the spread of disease? Check your answers. Are grapes grown in your area? If so, what pests are likely to cause damage? Are there any quarantine regulations for your area? If so, what are they? Summary Vine pests can spread through the soil, on cuttings or other vine material. Phylloxera is an extremely destructive insect pest of grapevines. The spread of phylloxera can be controlled by quarantine restrictions and planting vines with resistant rootstocks. Part 3: Pests and diseases of grapes 7

8 Fungal infections Fungal infections Grapevines are regularly monitored. The manager looks for signs of nutrient imbalance, weather damage or the presence of pests. Indications of pests might include: eaten leaves; the presence of spots or patches; small grapes or a poor berry set; yellowing leaves; or a powdery covering on grapes. Pests are identified and their damage levels determined. If necessary, control measures can be adopted. Anthracnose (black spot) is a disease caused by a fungus. Other common fungal diseases include downy mildew, oidium (powdery mildew), botrytis (bunch rot) and phomopsis (dead arm). Fungi reproduce by spores. Each fungus has different spores which can be used in identification. However, the damage is well underway when the disease is evident. That is why many of the pest control programs for these pests are preventative. Downy mildew Powdery mildew Botrytis on the underside of leaf on the leaf surface on the leaf surface clustered spores single strands clustered spores Features of the spores of three different diseases of grapevines. Many of the fungal diseases respond well to chemical sprays called fungicides. Information about the disease organism s life cycle and the favourable climatic conditions help to determine the best time to control the disease. Does the pest damage cost more than the control measures? The manager must know the value of the crop, the cost of the damage and the cost of control. When the damage costs more than control the economic threshold level has been reached. 8 Grape production

9 Black spot Pests can be identified in a number of ways. Very small pests can be identified by the damage they do. For example, black spot disease is identified by black spots on bark, leaves and berries. Some varieties, for example, Semillon, are highly resistant to black spot; others such as Grenache, are not. This diagram shows some of the symptoms of this fungal disease. Tell tale signs of anthracnose (black spot) on grapevines. Look at the grapevine in the following photograph. Evaluate whether you think it is infected with black spot. Grapevine. (Photograph by Julie Robinson) Check your answer. Part 3: Pests and diseases of grapes 9

10 Downy mildew Downy mildew was first detected in Australia, in Rutherglen, in Since then, it has spread to most of the vineyards in eastern Australia. Grape varieties vary in their susceptibility to downy mildew. For example, Pinot Noir vines are more susceptible than Cabernet Sauvignon. All green parts of the vine are affected. Circular oil spots on young leaves are an indication of the presence of downy mildew. Downy white spores are produced on the underside of the leaves (under the oil spots), on young berries and bunch stalks. Infections may cause the leaves on vines to fall, the flowers and bunch stalks to wither and the young berries to shrivel and harden, resulting in crop losses of up to 20%. During winter, spores rest on fallen and decaying leaves. In spring when temperatures are more than 10 C, the spores reinfect leaves. They are spread by rain splashing on the leaves. The spread of downy mildew is encouraged by conditions of high humidity. Many viticulturists carry out preventative programs, for example, regular spraying, in addition to canopy management to control mildew. The timing of fungicide application is critical. Vines are most susceptible to infection in warm, humid weather, so spraying is often done between budburst and berry development (in spring). Spraying equipment. Seldom seen vineyard, Mudgee. July, (Photograph: Julie Robinson) 10 Grape production

11 overhead sprinkler or rainfall wet leaves resting spores mobile spores spore (spring/ producing body summer) germination infection resting spores (winter) (late summer/ autumn) leaf fall fallen leaves Life cycle of downy mildew fungus. 1 Use information in the diagram to describe the life cycle of downy mildew in the vineyard. 2 Warm, wet and humid conditions favour the development of downy mildew. From your other work in this module describe two management practices which would help to control downy mildew. Check your answers. Part 3: Pests and diseases of grapes 11

12 Powdery mildew Powdery mildew is another fungal disease common in Australian vineyards. Like downy mildew, powdery mildew spread from North America to Europe and Australia. It appeared in Australia around All grapevines are susceptible to powdery mildew, though Riesling, Semillon and Chardonnay are particularly affected. pale green spots red brown areas grey white powdery patches (spores) poor berry set small berries mature grapes split dried out berries The effects of powdery mildew on a grapevine. 1 Outline how a severe infection of powdery mildew might affect the production of grapes. Infection by powdery mildew is encouraged by warm temperatures (optimum temperature is 25 C) and low light levels. At higher temperatures the spread of infection slows down. Ideal conditions are likely to occur between budburst and flowering. 2 Describe a disease management strategy for the control of powdery mildew in vineyards. Refer to your previous work for relevant information. 12 Grape production

13 3 Explain why timing is important in the control of powdery mildew. Check your answers. Fungicides There are a number of different fungicides registered for use in vineyards. These include: Bordeaux mixture ziram, mancozeb, benomyl sulfur, lime sulfur (very toxic to predators) copper oxychloride, copper hydroxide. The choice of a fungicide depends on environmental and economic considerations. It is also important that the control program is varied to avoid the pests building up resistance to chemicals. Rotating chemicals is one strategy used to prevent resistance, which is a major problem in some European vineyards. The use of other management strategies such as canopy management and the removal of dead leaves where some pests overwinter, will reduce the use of chemicals. Fungicides are usually applied more than once in a prevention program. Before spraying, the economic threshold of the pest problem must be considered. The vineyard manager needs to know: what type of disease is present or likely to occur (and when) how much the damage is likely to cost the cost of a spraying program the destination of the produce (wine, juice, table grapes, dried vine fruit) since different products have different quality requirements and chemical residue levels allowed. Part 3: Pests and diseases of grapes 13

14 Environmental consequences need to be considered when choosing to use particular chemicals on farms. For example, agricultural chemicals can: leave residues in farm produce or the soil, reducing quality leach through the soil profile to pollute ground water affect nearby crops or pastures when sprayed on a windy day vary in how toxic they are to humans affect soil organisms, bees, fish or birdlife. Information provided on container labels gives users guidelines. These must be read by the user. If the user cannot read English then the information must be read out to them. Organically grown grapes do not use artificial or synthetic chemicals. Sulfur and Bordeaux mixture can be used to control fungus diseases in organic vineyards. Complete Exercise 3.1: Bunch rot. Summary Fungi such as black spot, downy mildew, powdery mildew and botrytis interfere with grapevine production. Fungal diseases can be identified by their spores and the damage caused to the green parts of vines. Fungicides can be used to prevent and control fungal diseases of grapevines. Control programs are devised from information about the disease s life cycle and favourable climatic conditions. Pest control programs in vineyards include a range of strategies including spraying pesticides. In the next part you will be examining a holistic approach which takes account of the natural ecological balance of the vineyard working with nature instead of against it. 14 Grape production

15 The natural balance The natural balance Plants in nature seldom grow alone. They usually grow in a community whose characteristics depend on the environment they live in. For example, the plants and animals that live together in the tropics are quite different to those of the desert. The farm community On a farm, the natural community has been modified. Exotic plants and animals have been introduced. Some of these provide food and fibre; others are as escapees or hitchhikers. A vineyard community is shown below. parrots bees eucalyptus trees native and imported grasses sheep grazing wattle tree caterpillar Plants and animals living in a vineyard community. Some organisms are more obvious than others. Part 3: Pests and diseases of grapes 15

16 Agricultural activities Agricultural activities, for example spraying chemicals, alters the environment by changing the composition of soil and water, as well as plant and animal populations. machinery eg tractor and airseeder removal of products eg harvest, hay nutrients soil ph soil structure soil organisms Farming activities alter the environment. clearing for grazing and cropping biodiversity salinity erosion 1 Use the diagram to describe some of the changes that agricultural production makes to the environment. Give examples. 2 Chemical control of pests, diseases and weeds also affects the environment. From your knowledge of chemicals, briefly describe the effects spraying might have on the environment. Check your answers. 16 Grape production

17 Mites friend or foe? As well as bees, birds and fish, chemicals may affect the natural balance of mites in a vineyard. What are mites? These animals form part of a larger group known as arthropods. Other members include crabs, scorpions, ticks, centipedes and insects. Mites and ticks are part of a subgroup. Some are parasitic, for example, cattle tick. What balance are we talking about? In a vineyard, there are a number of different mites with various feeding patterns. Some mites, for example, bunch mite, blister mite and rust mite are considered pests because they feed on grapevines. Others are predatory; they feed on other mites. An understanding of the balance between pest and predatory mites is essential to the development of integrated pest management (IPM) in vineyards with mite problems. Mite research Understanding the population dynamics within each vineyard, and therefore the balance between organisms, is a major tool in the implementation of biological mite management. Research carried out by Dr David James and Jennifer Whitney at Yanco Agricultural Institute shows that some chemicals affect this balance more than others. Read about what Jennifer Whitney has to say about mite research in the transcript of an interview with her in the Additional resources section. 1 Jennifer mentions population dynamics several times during the interview. Outline what you think this term means. 2 From this research, explain how you think pest mites might be controlled by biological means. 3 Comment on the design of the research. Explain why you think this research was carried out in different vineyards over many years. Part 3: Pests and diseases of grapes 17

18 Check your answers. Chemical control of mites Chemicals used in vineyards affect mite populations. Sulfur sprays don t alter the mite populations too much but other harder chemicals are indiscriminate and may destroy all mite populations. Sulfur based sprays (except lime sulfur) usually do not affect mites too much. Vineyards where extensive chemical control is carried out have few, if any, of the native predator mites. Read about what Jennifer has to say about chemical control of mites in the interview in the Additional resources section. Jennifer relates the methods used to find out how fungicides and miticides used in vineyards affect mite numbers 1 Identify the information found by the first research method. Outline the conclusions that could be made. 2 Identify the information determined by the bioassay in the laboratory. Outline the conclusions that could be made. 3 Explain why research was carried out both in the field and in the laboratory. _ 4 Population dynamics and chemical sprays affect mite numbers in vineyards. Identify other factors that might influence mite populations. 18 Grape production

19 Check your answers. The influence of climate on mite populations The research involved looking at how different factors influenced mite populations. Read further in the transcript in the Additional resources section to find out how Jennifer finds environmental factors affect mite populations. Identify aspects of the research design that would have allowed the researchers to come up with these types of conclusions. Check your answer. Integrated pest management Pest populations need to be managed in vineyards to keep damage below the economic threshold. There are various strategies that may be used depending on things such as the vineyard manager s goals. Read the rest of the interview transcript in the Additional resources section to find out about the use of integrated pest management (IPM) in vineyards. In the interview Integrated pest management was described as being a responsible approach to pest control. Outline what is meant by the term integrated pest management. Check your answers. Part 3: Pests and diseases of grapes 19

20 Insect pests There are many insects that may be pests of grapevines. Some are sap suckers; others eat the leaves. Their activities reduce grape productivity. The table below shows the effects of some insect pests and common methods of control. Insect pest Damage Control lightbrown apple moth grapevine moth longtailed mealybug grapevine scale Rutherglen bug larvae hatch from eggs laid on weeds then eat leaves, young shoots, berries and flowers overwinters on vine wood or posts then eats leaves, flowers and young berries overwinters on vines, cover crops and weeds; secretes honeydew that develops into sooty mould; grape productivity is reduced overwinters on canes or wood; secretes honeydew which develops sooty mould; growth is restricted; young eat leaves normally lives among weeds; can kill young vines; reduces grape quality; eats all green parts predators, for example spiders parasites, for example Trichogramma insecticides, for example chlorpryifos biocide, for example Bacillus thuringiensis remove weeds predators, for example shield bug parasites of larvae and pupae insecticide, for example carbaryl biocide, for example Bacillus thuringiensis good canopy management insecticide, for example methidathion parasites, for example parasitic wasp predators, for example ladybird insecticide, for example winter oil control weeds where bugs breed insecticide, for example maldison applied to vine and soil where they lay eggs 20 Grape production

21 As you can see, there are various methods used to manage insect pests. Pests may be controlled by culture, natural, chemical or biological means. Write an example of each type of control. The first one is done for you. Control method Example Cultural control remove weeds, canopy management Natural control Chemical control Biological control Check your answers. If you were a vineyard manager how would you manage pests? Would you grow grapes organically? Why? Why not? Complete Exercise 3.2: Mites. Summary Many different plants and animals live in a vineyard community. Farming activities may upset plant and animal population dynamics. Biological control exploits the natural management of pest populations. Integrated pest management combines several control measures to manage pest populations. There are many insect pests of grapevines which are managed in a variety of ways. There are several types of fungi, mites and insects that interfere with grape production in a vineyard. In the next section you will examine the effects weeds have on production and how their populations can be managed. Part 3: Pests and diseases of grapes 21

22 Competitors Competitors It is common practice in agriculture to crop large areas. Most people are familiar with broadacre cropping, for example wheat, oats, barley, rice. Vineyards also have many plants in rows. Even in these highly controlled situations there are plant invaders called weeds. In this section, you will be examining various methods used to control weeds in vineyards. By comparing these you will be able to make recommendations for sustainable weed management strategies. Access an interactive version of Competitors using this link. This material will complete this part of the module. thistle young grapevine water nutrients Weeds compete for resources. Very simply, weeds are unwanted plants. Weeds, like cover crops, compete for valuable resources and may harbour pests. However, weeds can also harbour beneficial mites and insects. Weeds need to be managed since their total removal may not benefit the vineyard. 22 Grape production

23 Chemical control herbicides Herbicides contain an active chemical constituent. Usually they are mixed with water before spraying. It is extremely important that this is done safely and correctly. This includes getting the quantities right and wearing protective clothing. Your health and grapevine vigour are both at stake. So, read the instructions! General Protection of Livestock For control of... Protection of Wildlife Safety Directions First Aid Agricultural chemicals are required to include information on safety procedures, directions for use and environmental information. Identify at least four reasons why it is critical that farm chemicals are used safely and efficiently. Check your answers. Part 3: Pests and diseases of grapes 23

24 Types of herbicides In Australia, herbicides are grouped according to their mode of action the way they control weeds. There are fourteen herbicide groups (A N). These groups are rated as being a high, moderate or low risk. respirator Fusilade Group A Ally Group B [Group A-B] gloves Simazine Group C Treflan Group D [Group C H] Roundup Group M Diquat Group L overalls Risk [Group I N] Herbicides are labelled to show their group. This gives users an indication of their risk. Some herbicides are selective, they control only particular sorts of weeds. Examples include Treflan and Hoegrass. Broadspectrum herbicides, also known as knockdown herbicides, are not selective. Examples include Roundup and Gramoxone. There are a number of government authorities that regulate the production of chemicals used on farms. The efficient and safe use of farm chemicals is extremely important. In 1993, the Farm Chemical User Training Program was launched to assist people working on the land to more safely handle and better understand herbicide use on farms. 24 Grape production

25 Herbicides in the vineyard Chemicals used in vineyards must be registered for that purpose. The different sorts of herbicides are as follows. Pre-emergent herbicides - extremely effective for control of weeds before they emerge. They are residual chemicals usually sprayed onto bare ground. Some pre-emergents can accumulate in the soil. Contact (knockdown) herbicides kill weeds when they are touched. These herbicides are very effective at killing all the weeds they touch. Regrowth of weeds is unaffected. Systemic herbicides are translocated within the plant. They are very effective especially if they are applied when weeds are actively growing. The diagrams below illustrate the action of three different types of herbicides. Label each as either pre-emergent, contact or systemic. weed seeds all dead healthy dead healthy dead Check your labels. Part 3: Pests and diseases of grapes 25

26 Herbicide resistance One major drawback of chemical use is the build up of resistant weed populations. Many agricultural weeds have developed resistance to chemicals. These weeds can survive a herbicide applied at the recommended rate. Herbicide resistant weeds include annual rye grass, wild oats, capeweed, barley grass, dirty dora and starfruit. A number of non chemical strategies can be used to reduce the build up of herbicide resistant weeds. Agricultural plants should be grown under optimum conditions so they can successfully compete with weeds. Weeds can be cultivated, for example slashed, ploughed in. Crops can be grown to compete with weeds, for example a cover crop, pasture, green manure crop. Weeds can be smothered by mulching or composting. Weeds can be grazed by sheep in winter. Part of a weed management program may however, include chemical use. When using chemicals as part of a weed management strategy farmers should: rotate chemicals from different groups try to use low and moderate risk chemicals use knockdown herbicides before cropping spray weeds before they set seed (spray topping, crop topping) analyse herbicides when the weeds are out of control. It is important to keep accurate paddock records that show which herbicides were used in which paddock and when. Is resistance to herbicides something that farmers really need to be concerned about? Why? Why not? Complete Exercise 3.3: Resistance. 26 Grape production

27 Organic weed control There are production standards that must be met by organic grape growers. Synthetic chemicals are not allowed for use in organic vineyards. Methods of control that are acceptable include: mechanical or cultural control, for example hand weeding, cultivation with machinery, mulching planting cover crops biological control. Mechanical/cultural control Weeds in vineyards can be slashed, mowed, or cultivated. However, this may damage the vine or its root system. Cultivation was the most common form of weed control before modern herbicides were developed. Now, mechanical cultivation is less popular because of the soil damage that may occur. Think about the advantages and disadvantages of mechanical cultivation. Complete the table to list at least two advantages and two disadvantages of cultivating weeds. Advantages Disadvantages Check your answers. Part 3: Pests and diseases of grapes 27

28 Cover crops Planting cover crops in vineyards can reduce weeds. However, there are advantages and disadvantages as show in the table below. Advantages Disadvantages provides nutrients, for example, legumes competition for water improves soil structure competition for nutrients additional produce, for example, hay can host pests reduces weeds competition for space reduces erosion may shade other plants 1 Briefly explain, using examples, three advantages and three disadvantages of using cover crops in vineyards. One advantage is shown below. A legume cover crop, for example lucerne, may increase the nitrogen levels in the soil. 2 Discuss whether you would grow a cover crop if you were a vineyard manager. _ Check your answers. 28 Grape production

29 Biological control In the last part you learned how effective predator mites were in the control of blister, rust and bunch mites on grapevines. The natural enemies of weeds work in essentially the same way. Biological control of weeds uses natural enemies such as insects, mites and pathogens. There are rigorous procedures that must be followed before biological control agents (natural enemies) can be released. The Australian Quarantine Inspection Service (AQIS) and Environment Australia must approve their importation into Australia. A series of tests must ensure that the agent attacks only the target. This ensures the safety of native species. An application for release of the biological control agent must be approved by several government departments, research organisations and state departments. The effect of the control agent must be observed in quarantine. Performance in the field is monitored at research sites. Biological control does not eradicate pests. It does, however, offer a natural, environmentally safe long term method of control. Many different organisms have been released as biological control agents. For example, the CSIRO has released a rust fungus for skeleton weed management. Read the article Weevil causes destruction on Paterson s curse in the Additional resources section. It outlines the release of a biological agent used in the control of Paterson s curse, otherwise known as Salvation Jane. This research is being done by Dr Andy Sheppard. As you read, think about the potential of this form of control and any possible drawbacks. 1 Identify at least two advantages in using biological weed control. 2 Identify at least one disadvantage in using biological weed control. Part 3: Pests and diseases of grapes 29

30 3 Evaluate biological control of weeds considering the advantages and disadvantages you have identified. Check your answers. Plant associations You may have heard of companion planting where plants are grown next to a crop to benefit the crop s growth and development. For example, growing basil with tomato plants benefits the crop in ways that are not entirely understood. The basil may deter insect pests that would otherwise damage the tomatoes. The weed, silverleaf nightshade reduces the growth of crop and pasture plants. Studies suggest that the roots of silverleaf nightshade release a chemical which stops the growth of other plants. The affects of one plant on another may be beneficial or adverse. This is called allelopathy. Allelopathy is another example of crop interference. The effects of some plants on others have been observed for a very long time. Democritus in the third century BC first recorded that some plants don t grow near others. Molisch coined the term allelopathy to describe this effect in The term was coined from the Greek words below. allelon of each other; pathos to suffer Plants that lower crop yields include parthenium, Johnson grass, cotton, purslane and lantana. These plants don t affect all plants. They are selective. For example; tall fescue inhibits the growth of canola and red clover; thistles affect oats; and rye inhibits wheat. There is little known about allelopathic plants and grapes. Allelopathic plants affect other plants in a variety of ways. The chemicals released can: make seeds and buds dormant promote disease infections make plants more susceptible to disease disrupt water balance interfere with photosynthesis 30 Grape production

31 interfere with nitrogen fixation slows down the uptake of nutrients. What are the implications? Allelopathic plants can cause problems in many agricultural enterprises. For example, as weeds in crops and pastures, as stubble mulch for the next crop, in crop rotations, when orchards are replanted and when forests are regenerated. Research into allelopathic plants may result in isolating chemicals that can be used in weed control. Complete Exercise 3.4: Interference. Summary Weeds compete for resources, reducing plant productivity. Weeds can be managed in a variety of ways. They can be: slashed by machinery grazed by sheep sprayed with herbicides attacked by biological control agents covered with mulch or compost smothered by a cover crop. A combination of non chemical strategies is recommended to reduce the build up of herbicide resistant plants. Some plants have an allelopathic affect on another. Methods used to control weeds, pests and diseases of grapevines are changing. In fact, many things are different. In the next part you will be finding out what s new in viticulture. Part 3: Pests and diseases of grapes 31

32 Additional resources Additional resources Interview with Jennifer Whitney Jennifer Whitney at Yanco Agricultural Institute has researched the biological control of grapevine mites for seven years and shares her experience with us in the following interview. Mite research How did you gain knowledge of the balance that exists between organisms in vineyards? To obtain this knowledge, we have to understand the population dynamics of pest and predatory mites in each vineyard. Population dynamics display regional differences, although regional trends are usually obvious. Within regions, the population dynamics can vary considerably from vineyard to vineyard depending on management practices used,, for example, use or non use of chemicals. We studied the population dynamics of individual sites the following ways. Sites were selected in viticultural regions across Australia. Most sites selected were low input (minimal chemical usage) sites to give a more accurate reflection of the natural grapevine fauna. Some sites that received conventional spray programs were also used as a comparison. Grapevine material (leaf, shoot, cane) was sampled from each site throughout the season (August to May). Material was returned to the laboratory and examined using a stereomicroscope. Pest and predatory mite numbers were recorded and the occurrence of other fauna was noted. Predatory mites were collected and retained in alcohol for later species identification. Pest and predatory mites numbers were collated and graphed at the end of each season. Comparison of these data over several seasons gave us a detailed picture of the population dynamics of these mites. Predator species identifications were done. This provided a species profile for each site and region and gave us an indication of how effective they were as pest control agents. Studying mite numbers for extended periods therefore provides information on pest and predator populations and their affect on each other. 32 Grape production

33 Chemical control of mites What are the effects of chemical sprays on mite populations? In most vineyards, chemicals are applied mainly for disease control, although some miticides and insecticides are still used. Although these products are aimed at diseases, they can still have a detrimental effect on the natural grapevine fauna. We therefore need to understand their effects on predators. We determined the effects of chemical sprays on mites in two ways. At the end of each season, we obtained seasonal spray information from each grower or vineyard manager. This information contained product details, rate of application and date of application. This information was incorporated with details of pest and predatory mite populations for the same site. Using a graphical representation of the mite fauna in each vineyard, we were able to see the effects of chemicals on mite populations throughout the season, by determining the chemical application date from the graph. Any effect on mites can be easily seen. In some cases where chemicals were applied for pest mite control, an initial decline in numbers was apparent as well as a drop in predators. This was usually preceded by a pest mite outbreak! Clearly, when predators are reduced, pests are not controlled. Another method of determining the effects of chemicals on predatory mites is by laboratory bioassay technique. That is, exposing predators to selected volumes of chemicals and monitoring the survival rate. The influence of climate on mite populations How do different environmental factors affect mite populations? Environmental factors affect pest and predatory mite populations seasonally and geographically. Our studies show that pest mite outbreaks are usually reflective of each season s climatic characteristics. That is, bunch mite being more prevalent in the warmer grape growing regions and rust mite usually prevalent in the cooler grape growing regions. The study of population dynamics, as detailed above, has enabled us to observe these trends in pest mite outbreaks, but in most seasons, we still see varying combinations of the three main grapevine mite pests bunch mite, rust mite and blister mite. The occurrence of predatory mites is more of a geographical/ environmental factor. Some species of predators prefer the warmer inland regions of Australia, while others occur in the cooler, more southerly climes. We are also aware of several species of predator that are only found in coastal regions and likewise others, that prefer inland habitats. Continued monitoring of regular sites over many seasons has allowed us to gain comprehensive knowledge of the predatory fauna on Australian grapevines. This understanding allows us to recommend regional strategies for biological mite management. Part 3: Pests and diseases of grapes 33

34 Integrated pest management How can integrated pest management (IPM) in vineyards be achieved? Our knowledge of IPM in vineyards is derived from the above information. Understanding population dynamics at a regional level, enables the appropriate regional recommendations to be made, for example, suitable spray programs, techniques for enhancing the natural vineyard fauna via cultural and management practices etc. Therefore, IPM is a responsible approach to pest management, combining the maximum use of natural management practices, with chemical control measures only when required. Predators control mites in vineyards By David James and Jennifer Whitney A revolution is about to occur in vineyard mite control. Miticides will soon be replaced by two attractive predatory ladies with enormous appetites for the mite pests of grapevine bunch mite, blister mite and rust mite. Doreen (Typhlodromus doreenae) and Victoria (Amblyseius victoriensis) are predatory mites of the Phytoseiidae family and they spearhead the push toward reduced chemical usage in grapevines. Doreen and Victoria are Australian through and through and have been trying to invade inland vineyards to feed on pest mites ever since viticulture began in these areas. However, until now their efforts have been thwarted by a barrage of chemical sprays aimed at vine diseases, insect pests and mites. Vignerons have done an excellent job in keeping Doreen and Victoria (and no doubt many other useful organisms) out of their vineyards. Everywhere, that is, except the Riverlands in South Australia. Here, viticulturists have opted for the use of inorganic compounds such as sulphur and copper to control diseases such as powdery and downy mildew. They rarely use the newer systemic fungicides which can really spoil a predatory mite s day. Consequently, Doreen is a full time inhabitant of Riverlands vineyards. She is able to put up with the regular applications of sulphur and copper and produces populations which can occupy 90% of the leaves in a vineyard. Doreen is fond of feeding on bunch mites and normally if Doreen is present then the bunch mites are scarce or absent. A big attribute of Doreen is that she does not disappear when she eliminates her favourite food. Unlike a number of other predatory mites used in horticultural crops, Doreen is not dependent on a single food resource for survival. She will also feed on rust and blister mites and when times get really tough will eat pollen, insect eggs and honeydew. Consequently, it is common to find large Doreen populations, but no mite pests on Riverlands grapevines. Victoria is also a general feeder, but tends to prefer rust and blister mites and therefore complements the bunch mite preference of Doreen. Unlike Doreen, which remains on grapevines throughout the year, Victoria departs with the leaves in autumn and returns early-mid summer. Her return is largely influenced by sprays used. Unlike Doreen, Victoria is susceptible to sulphur. 34 Grape production

35 The Doreen and Victoria combination generally hits its stride in January and thereafter bunch, blister and rust mites are a rarity in Riverland vineyards. Of course, no one knew Doreen and Victoria were performing such an excellent service until vineyard mite fauna was examined in 1989/90. Riverlands growers had been applying two to four sulphur sprays a season to control mites, a production cost which was totally unnecessary. Viticulture in the Murrumbidgee Irrigation Area and Sunraysia is characterised by greater inputs of synthetic fungicides which are generally more detrimental to predatory mites than sulphur and copper. Victoria is common in both regions, but does not appear on grapevines until sprays cease. Doreen has only been recorded once on MIA grapevines. It is likely that Doreen and Victoria could establish that same winning partnership in Sunraysia and the MIA if predator-friendly chemicals were used. Recent studies in Canberra vineyards have shown Doreen is alive and well in this region and clearly must have the ability to survive cold and hot conditions! Chemical mite control costs the Australian grape industry an estimated $2.8 million per annum. Doreen and Victoria have the potential to remove most of this cost from grape production. Research is now being directed toward developing and implementing biological control strategies for grapevine mites in all leading viticultural regions of southeastern Australia. Strategies will be based on the successful Riverlands model either using Doreen and Victoria or other predatory mites already present in the regions. An important research area is development of a mass rearing technique for Doreen and Victoria. If commercially available, these predators will be rapidly introduced to vineyards without them. The Doreen and Victoria story is an excellent example of the substantial benefits from basic biological research into previously unstudied systems. Doreen and Victoria and their ilk have the potential to save the viticultural industry millions of dollars in production costs. They will also ensure a less contaminated product and help to clean up the environment. Good Fruit and Vegetables. Rural Press. Issue No. 2. (1992). Part 3: Pests and diseases of grapes 35

36 Botrytis Botrytis is fungal disease that affects many of Australia s vineyards. Varieties that are prone to botrytis (also known as grey rot) include Semillon, Chardonnay, and Sauvignon blanc. soft rot dead tissue watery spots skin splits Grapevine shoots, leaves, flowers and berries can be infected by botrytis. Steve Warne is a winemaker for De Bortoli Wines in Griffith in the MIA. The De Bortoli family company produces a large range of wines which includes Noble one, a botrytised dessert wine of exceptional quality. Steven was asked about the effect botrytis has on grape production. Following is his comment. Botrytis can have a positive or negative effect on grape production. One of the negative effects is that it reduces grape quality. There are problems in processing with juice stability etc. These can be overcome, but at a cost. On the positive side, an exceptional dessert wine can be produced under the right conditions. The initial infection is produced under conditions of high humidity. If grapes are allowed to dehydrate so that the sugar content increases then noble rot develops. In this area, cloudy foggy mornings followed with clear days produces the right conditions. This varies from area to area with some areas better than others. This may be due to differences in air drainage. Canopy training and other management practices also affect botrytis infections. There are a number of fungicides that can be used to control botrytis. The main site of infection is the flower. This fungus overwinters in the old dried berries and other vine material. Timing is critical in fungus control. It must be knocked out before flowering. 36 Grape production

37 De Bortoli Wines started producing botrytised dessert wines in It was seen as a marketing opportunity, an industry trailblazer. The symptoms of infection are easy to see. In the advanced stages a hairy sort of mound covers the fruit. Earlier, grapes are papery, pinkish and easy to break. The fruit used to produce Noble one looks pretty disgusting with mould all over the fruit. flower overwintering wind new shoot flower infection spores (spring) wind dormant fungus (winter) dormant fungus (winter) dried out grapes Life cycle of Botrytis cinerea (bunch rot). Part 3: Pests and diseases of grapes 37

38 Herbicide resistance management program - It s your move Herbicide resistance is a major threat facing Australian grain growers. Pressure on growers to rely more heavily on Group A and Group B products will result in increasing discoveries of resistant populations of annual ryegrass, wild oats and broadleaf weeds. However, resistance can be managed and a Grains Research Development Corporation National Extension Program has helped raise national awareness of this problem. In 1992 State agricultural agencies, Avcare, weed researchers and GRDC put in place a program to address herbicide resistance, a major threat facing Australian grain growers. Projects were funded in Southern Queensland, Northern and Southern NSW, Victoria, Tasmania, South Australia and Western Australia. These projects had the common aim of raising awareness of herbicide resistance and to extend information on how to avoid and manage this problem. A major feature of the program has been the cooperation and interaction between the coordinators; researchers; advisers from government, private and corporate sectors; the Herbicide Resistance subcommittee of Avcare; key farmers and farmer groups. This cooperation has lead to a greatly improved understanding with both the avoidance and management of herbicide resistance. A key achievement of the program has been the agreement to make it mandatory for all herbicide labels to include the mode of action group for each chemical. Outputs and activities of the projects include the following: WA Herbicide Resistance Reference Manual Weed Smart booklet - used in 1993 and 1994 Tasmanian Herbicide Resistance awareness and management package the 1994/95 and 1996 awareness brochures articles on resistance in a wide range of weed control charts, books, magazines, etc posters workshops, seminars, conferences and training programs for farmers and advisers packages for advisers and Farmcare training providers,, for example, overhead and slide transparencies procedure for a field test for resistance displays and presentations at major field days, conferences and local programs audio-visual using slides for use at major field days and conferences, which has been put onto video for use with smaller groups. 38 Grape production

39 Has the program made any difference? The coordinators are confidant that the answer is yes. Most grain growers are now aware of herbicide resistance as a potential problem on their farms. Good understanding however, about how to avoid, delay or manage resistance is mostly confines to those farmers who have recognised the problem on their own farm or nearby. Such farmers are proving that resistant weed populations can be managed in a manner that improves the prospects of profitable production. This is only being achieved where farmers are prepared to reduce reliance on the highly effective Group A and B products to use a wide range of methods to control crop weeds such as annual ryegrass, wild oats and Indian Hedge mustard. The awareness and understanding of those advising farmers has improved significantly over the three years of the program ( ). With increasing economic burdens and in some cases falling herbicide prices growers are going to be under more and more pressure to rely heavily on Group A and Group B products for weed control in intensive grain growing areas. The potential for resistance in broadleaf weeds to Group B products is of major concern to the coordinators and resistance researchers and highlights the need for continued research and extension effort on the prevention and management of resistance weeds. Cooperative Research Centre for Weed Management Systems. Research highlights. Weed Watch. Issue number 3. March June Cooperative Research Centres Program. Australia. Weevil causes destruction on Paterson s curse The last issue of Weed Watch reported that Paterson s curse root-crown weevil Mogulones larvatus, first released by CSIRO Entomology researchers, were developing in large numbers at a release site near Yanco. Since that time the weevils have undergone a further generation with devastating results. On an organic farm the weevils have killed all plants within a 200 m radius of the release point (an estimated plants). This has occurred in the absence of plant competition and isolated pockets of healthy plants that have not been so heavily hit prove the damage can be attributed to the weevil. Such damage levels are much higher than those ever recorded in the native range and beyond the expectations for the project personnel. This holds well for the next biological agent redistribution workshop due to be held at Yanco next autumn. If such attack levels continue to spread and start to appear elsewhere at other younger release sites we may be seeing the start of something big! An interesting observation is that the biggest plants died first. This site will be closely monitored in future seasons and will be used as the main harvesting site for further distributions throughout NSW. Cooperative Research Centre for Weed Management Systems. Research highlights. Weed Watch. Issue number 3. March June Cooperative Research Centres Program. Australia. Part 3: Pests and diseases of grapes 39