Tomato infectious chlorosis virus (TICV)
Whitefly (Trialeurodes vaporariorum)
Symptoms first appear on older leaves as interveinal yellow blotches while the veins themselves remain green. Symptoms progress to the younger leaves, and depending on the variety, the interveinal yellowing can become bleached-white or necrotic. The affected leaf tissues are brittle and can be easily crushed, and the fruit color may be affected. Severe losses due to poor fruit set have been reported in Southern California. Symptoms caused by this disease can easily be mistaken for problems caused by poor growing conditions, aging or nutrient deficiency.
Conditions for Disease Development
First reported in 1993, TICV has been found to be transmitted in a semi-persistent manner by the greenhouse whitefly. This virus is spread in the greenhouse when virus-carrying whiteflies move from infected to healthy plants. The virus is not seed borne, nor can it be transmitted by touching or pruning plants. Once acquired by the whitefly, the virus remains infectious in the insect’s body for a few days. Plants begin to develop symptoms a few weeks after infection. Early infection can result in severe yield loss in certain varieties.
Since the greenhouse whitefly is the only vector for this virus, controlling the insect is generally the most effective control practice. A routine spray program in combination with covering openings to prevent the whitefly from entering the greenhouse should be implemented to keep the insect’s population low. When the crop is finished, all plant materials should be removed from the greenhouse and a plant-free period should be implemented. Transplants should come from a whitefly-free greenhouse.