Greening and Canker Training for Master Gardeners

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1 Greening and Canker Training for Master Gardeners Ryan Atwood, Extension Agent, Lake County & Dr. Tim Spann, Extension Specialist, Citrus Research and Education Center Created: September 2007

2 Citrus in Florida Citrus arrived with Spaniards- St. Augustine 1565 Adapted well to soil and climate Florida s identity is closely linked with citrus; when people think of Florida they think citrus

3 Citrus in Florida- Economic Impact Florida supplies most of the orange juice produced in the U.S. 575 million gallons NFC, 85 million gallons FCOJ ( ) Florida produces one-third of the world s grapefruit 10,000 property owners grow citrus in commercially Florida

4 Citrus in Florida- Economic Impact 150,000 people work directly or indirectly for Florida s citrus industry On-tree value of fruit $1 billion The citrus industry and the jobs and businesses that support it generate $9 billion for Florida s economy

5 Citrus in Florida- New Challenges Rapid Urbanization- Loss of acreage Labor shortages- Guest worker program and immigration reform issues Bacterial Diseases- Greening (HLB) and Canker New nursery regulations - reduced availability of trees

6 Master Gardeners & Homeowners The health of Florida s citrus industry requires cooperative effort from backyard citrus growers to combat bacterial diseases. Without homeowner cooperation current management practices will fail. Master Gardeners can help identify diseases and educate the homeowner on the significance of bacterial diseases to citrus industry.

7 Citrus Canker Citrus canker is caused by a bacterial pathogen Xanthomonas axonopodis pv. citri. The disease causes necrotic lesions on leaves, stems and fruit. Severe infestation can cause defoliation, fruit drop, twig dieback, general tree decline, and blemishes on fruit.

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11 Citrus Canker When there is moisture on the lesions, the bacteria ooze out and can spread to new growth or other trees. Wind driven rain is the main dispersal agent, and wind speeds greater than 18 mph aid in the penetration of bacteria thru stomatal pores or wounds.

12 Citrus Canker Movement of infected or exposed trees, seedlings, propagative material, and fruit is the primary means of spreading the canker pathogen over long distances. Contaminated clothing, tools, landscaping equipment, ladders, or containers are potential sources of infection. Decontaminate all equipment associated with citrus tree work (70% alcohol solution)

13 Current Map of Citrus Canker Distribution in Florida The urban areas with citrus canker are shown in red

14 Quarantine regulations USDA has the state of Florida under quarantine all fruit must be inspected and have a permit before shipping out of state No commercial shipments allowed to other U.S. citrus producing states and territories Arizona, California, Hawaii, Louisiana, Texas American Samoa, Guam, Northern Mariana Islands, Puerto Rico, U.S. Virgin Islands No homeowner shipments are allowed to anywhere outside of Florida

15 Current citrus canker quarantine zone status for residential areas Citrus can be replanted in citrus canker quarantine areas, but must be purchased from certified nurseries that are registered with the state. Decontamination requirements have been lifted for lawn maintenance companies. Citrus material (trees, fruit, rootstock, leaves, potted citrus plants, etc.) may not be moved from Florida.

16 If called on the telephone regarding citrus canker Ask the homeowner if they could take a digital photo of the symptoms and a copy to the clinic for identification. If you cannot make a definitive identification, forward the photo to your local citrus extension agent. If a diagnosis cannot be made from the photo, have the homeowner call the DPI Canker and Greening Helpline ( ) to have an inspector look at the tree.

17 What should I do if a homeowner has canker? If the tree is determined to have citrus canker provide literature for further information and management recommendations. Do not transport samples from suspected trees (including bring samples to county extension offices) due to the risk of spreading the disease. If infection is severe, tree removal would be wise, but not mandatory.

18 If a canker sample is brought into the extension office Samples received at the office suspected to have canker should immediately be double bagged (two clear zip-top bags). After diagnosis, sample can be thrown in the waste as long as it is double bagged. Sanitize counters, equipment, and your hands if they may have come into contact with suspect citrus samples (Rubbing alcohol and antimicrobial soap recommended).

19 Citrus Canker - Management Early oranges are most susceptible to canker, with tangerines being the most tolerant. Leafminer control is essential. Leafminer tunnels greatly increase the chance of canker infection. Spray horticultural oils for leafminer control beginning in early May.

20 Citrus Canker - Management For trees not infected with canker, following decontamination procedures is important. If you find canker lesions on you tree, pruning and removing the infected material will reduce the inoculum level; care has to be used to avoid spreading the bacteria during this process. Infected plant material should be sealed in two plastic bags and disposed of in the trash.

21 Citrus Canker - Management Copper products are effective in preventing fruit infection, less effective in preventing leaf infection, and have limited value in reducing spread of disease. Copper sprays should be used every 3 to 4 weeks between mid- May to mid-july. For proper rates follow the label.

22 Citrus Greening

23 Huanglongbing (Citrus Greening) Huanglongbing (HLB), referred to as citrus greening, is a disease caused by a bacterium (Candidatus Liberibacter spp.) that lives in the phloem (bark) of infected trees This disease affects all citrus types and eventually causes tree decline. Infected trees produce misshapen, unmarketable, bitter fruit, unsuitable for sale as fresh fruit or for juice

24 Huanglongbing (Citrus Greening) No cure once a tree is infected Trees usually decline within 3-5 years of infection, and ultimately die In areas of the world affected by greening tree lifespan has gone from 50+ years to < 15 years Tree removal only known effective control

25 Huanglongbing (Citrus Greening) Citrus greening is transmitted by the Asian citrus psyllid, which came to Florida in Citrus greening was first detected in S.E. Florida in August of 2005.

26 Current Map of Greening Distribution in Florida

27 Greening - Symptoms First symptoms of yellow shoot Blotchy mottle or variegated type of chlorosis with small upright leaves Heavy leaf and fruit drop with off season flush and bloom Severely infected trees - stunting, sparse foliation, die back Fruit small, lopsided with bitter salty taste and remain green on the end

28 Greening Yellow shoot

29 Greening- Blotchy Mottle

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32 Greening Sparse Foliation

33 Greening Abnormal Fruit Fruit are small, misshapen and do not color properly Fruit have a salty, bitter taste and are not suitable for eating

34 Greening or Nutrient Deficiency? Zinc deficiency Greening symptoms

35 Greening or Nutrient Deficiency? Must be confirmed by a molecular test polymerase chain reaction (PCR) PCR most reliable with symptomatic tissue Division of Plant Industry (DPI) will take samples for testing

36 Greening Disease Transmission The Asian citrus psyllid transmits the pathogen Psyllids fly or are carried by wind to new plants and spread the disease Greening is not spread by contact, tools or equipment

37 Asian Citrus Psyllid 5 nymphal stages Ten generations per year Life cycle between days Egg to Adult in two weeks at F From: D.L. Caldwell, UF

38 Greening - Transmission Psyllids pick up the bacterium by feeding and can transmit it to healthy trees Acquisition is by adults and large nymphs (4 th and 5 th instars) Psyllids remain infected for life

39 Greening - Transmission Less than 7 hours of feeding is required for psyllids to transmit the pathogen to a healthy tree Infected plant material (both citrus and ornamentals) may or may not show symptoms

40 Greening Non-citrus Hosts Orange Jasmine (Murraya paniculata) is a host of both the psyllid and greening bacterium In Brazil, greening was introduced to Parana State through infected orange jasmine plants Photos by: Forest & Kim Starr Murraya with greening symptoms in Parana State, Brazil

41 Greening Non-citrus Hosts Chinese box orange / boxthorn (Severinia buxifolia) is another ornamental host of greening and the Asian citrus psyllid Chinese Box Orange / Boxthorn

42 Greening - Management Surveying & Removal of Symptomatic Trees Disease-free nursery stock Manage psyllid populations Cultural techniques

43 Greening - Management You cannot prune away a greening infection Greening is systemic i.e. throughout the plant When removing an infected tree be sure to kill the stump with a herbicide to prevent sprouting. Sprouts will contain the bacteria and be a source of inoculum.

44 Greening Management Eliminating host plants and encouraging beneficial insects is the best approach. You CANNOT prevent infected psyllids from flying into your yard and infecting healthy trees. Chemical controls for psyllids are extremely limited for homeowners. Horticultural oils will offer some control if direct contact is made with psyllid adults and nymphs.

45 Suppression of Psyllid Populations Biological Control There are numerous natural enemies (beneficial insects) present that suppress psyllid populations, especially in the summer and fall Over 90% of psyllid nymphs are consumed by predaceous insects such as ladybeetles

46 If called on the telephone regarding greening Ask the homeowner to a digital photo of the symptoms to the clinic for diagnosis. If the photo looks suspect, forward it to your local citrus extension agent or state citrus extension specialist. If the tree is suspected to have citrus greening have the homeowner call the DPI helpline to schedule a DPI inspector to examine the tree.

47 If a greening sample is brought to the extension office Samples received at the office should immediately be double bagged (if not already) to prevent the spread of psyllids that may be present. If the sample is suspected to be greening, the homeowner should contact the DPI Helpline to arrange for a laboratory PCR test for verification.

48 What to tell a homeowner with a greening infected tree If a tree has tested positive for citrus greening, removal is recommend. Explain to the homeowner that it is just a matter of time before the fruit become inedible and the tree dies. If they choose not to remove the tree, it will be a source of inoculum to spread the disease to other trees in their area.

49 Questions?