Cooperative Extension Service 
________________________________________________
Institute of Food and Agricultural Sciences
 
Hendry County Extension P. O. Box 68 LaBelle, Florida 33975-0068 Phone (863) 674-4092

Hendry County Horticulture News

Tomato Yellow Leaf Curl Virus - A New Threat to Florida Gardeners

The latest imported pest problem in Florida is the tomato yellow leaf curl virus (TYLCV).  This disease probably entered Florida in the  spring of 1997 from the Caribbean in the form of infected plants, plants hosting infective whiteflies or most directly by wind carried virus-bearing whiteflies.  The vector and virus has entered into transplant production nurseries and has been distributed within Florida to homeowners by way of several retail department stores.  To date, this virus has been found in retail outlets in the southeast, southwest and north central areas of Florida and has been inadvertently shipped out-of-state as well.  In the past few months this disease has become more active in south west Florida.

TYLCV is one of more than a dozen plant viruses that can infect tomatoes in both the home garden and commercial production fields in Florida.  In contrast to the other viruses, the impact of TYLCV can be quite severe - virtually eliminating fruit production when plants are infected at an early age.  The virus is spread plant-to-plant by the silverleaf whitefly.  These insects can rapidly acquire this virus by feeding on an infected plant. These infected whiteflies can then retain the virus for 10-12 days and introduce it into any number of healthy tomatoes during feeding periods.   Unlike other common tomato viruses in Florida, TYLCV does not survive in soil, on tomato stakes, wire or string and cannot be moved mechanically through such common activities as tying plants or picking fruit.  This virus can survive in other crops and weed species but the important host range for this virus in Florida is as yet unknown.

How do you diagnose the disease?  TYLCV can cause a range of symptoms that include marginal leaf yellowing, upward or downward leaf cupping, reduction in leaf size, flower and/or fruit drop, and plant stunting.  It is important, however, to realize that not all the above symptoms exist at the same time and more importantly, that these individual symptoms are not specific to TYLCV or even viral diseases in general.

When plants are purchased from a retail outlet and planted in the garden, TYLCV may exist in one to all the plants.  The earliest symptoms to observe will be marginal leaf yellowing of the newest leaf or leaves with mild cupping.  Due to plant age, symptoms like plant stunting and flower and fruit abortion will not be evident as yet.  When tomato transplants are purchased from more than one source, early symptoms of TYLCV can be perceived more easily by the contrast among infected and non-infected tomatoes in the garden or between nearby garden plots.  As infected plants age, the more dramatic symptoms of yellowing, (plants have been described as glowing with a yellow light), leaf cupping, reduction in leaf size, flower drop and plant stunting can be observed - especially when healthy tomatoes are nearby for comparison.

The visual diagnosis of TYLCV is most accurate when two or more symptoms can be confirmed from the same plant.  Identification of  TYLCV based upon just marginal leaf yellowing or slight leaf cupping can lead to mistakes.  Single symptoms may have other possible causes when they develop in tomato.  Contact the Hendry County Extension Office for help in identifying the disease.  Color pictures are available at the Hendry County Extension Office (Plant Pathology Circular 1143) , and on the Web at http://hammock.ifas.ufl.edu/new/pg08400.htm.

Management of TYLCV is a multi-step strategy.  Plants suspected of infection should be rogued from the garden and destroyed in the following manner:

1) symptomatic plants should be carefully covered by a clear or black plastic bag and tied at the stem at soil line.  Cut off the plant below the bag and allow bag with plant and whiteflies to desiccate to death on the soil surface for 1-2 days prior to placing the plant in the trash.  Do not cut the plant off or pull it out of the garden and toss it on the compost!  The idea is to remove the plant reservoir of virus from the garden and to trap the existing virus-bearing whiteflies so they do not fly onto other tomatoes.

2) If symptomatic plants have no obvious whiteflies on the lower leaf surface, these plants can be cut from the garden and buried in the compost.

3) Inspect plants for whitefly infestations two times per week.  If whiteflies are beginning to appear, spray with azadirachtin (Neem), pyrethrin or insecticidal soap.  For more effective control, it is recommended that at least two of the above insecticides be rotated at each spraying.  Follow label directions closely for dosage rates, spray intervals and precautions.  Be sure to spray the undersides of the leaves thoroughly.

Although this particular disease has not been a big problem in our area, it is becoming more active and is particularly destructive on tomatoes.  Awareness and vigilance by local gardeners and farmers alike may help prevent it from getting established in southwest Florida.  Good luck and good gardening.

Gene McAvoy is the horticulture agent with the Hendry County Extension Service.  Direct your horticulture questions to PO Box 68, LaBelle, FL 33975,  e-mail - gmcavoy@gnv.ifas.ufl.edu or phone 863-674-4092 or  863-983-1598.  You are also welcome to visit the Hendry County Extension Office at 225 Pratt Blvd., LaBelle.   Office hours are from 8:00 - 5:00.

The Institute of Food and Agricultural Sciences is an Equal Employment Opportunity - Affirmative Action Employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap or national origin.
COOPERATIVE EXTENSION WORK IN AGRICULTURE, FAMILY AND CONSUMER SCIENCES, SEA GRANT AND 4-H YOUTH, STATE OF FLORIDA, IFAS, UNIVERSITY OF FLORIDA, U.S. DEPARTMENT OF AGRICULTURE, AND BOARDS OF COUNTY COMMISSIONERS COOPERATING

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