Tomato chlorosis virus was first detected in greenhouses, but the disease has since moved out into the field to become a potentially serious pest.
The viral disease, commonly refered to as ToCV, can be spread by several whiteflies, although the silverleaf is the most efficient, Charlie Mellinger, an owner of Jupiter-based Glades Crop Care writes in a newsletter.
A related virus, tomato infectious chlorosis virus (TICV) occurs only in the western United States and has caused major losses.
This disease is not a threat to Florida agriculture because it is vectored only by the greenhouse whitefly, which is currently not an economically important pest.
Transmission of ToCV is relatively efficient; whiteflies can transmit the virus with feeding times as short as an hour. But they become more efficient the loger they feed. The most efficient transmission occurs after two to three days of feeding.
Unlike tomato yellow leaf curl virus, which can be transmitted during the whitefly's entire life, ToCV tranmission only occurs for one to nine days after feeding.
identifying ToCV can be difficult, as its symptoms are similar to nutrient deficiencies or herbicide toxicity. Symptoms include
interveinal leaf chlorosis, leaf brittleness, reduced vigor and early senescence.
The middle to lower parts of the plants typically are the most severely affected while the tops of the plants can appear normal.
Glades Crop Care scouts have observed this virus in a few Immokalee area tomato farms during the spring 2007 season at an incidence of 5 percent to 10 percent, Mellinger writes. During spring 2008, the incidence on some farms was much higher.
In addition to whitefly, several weed hosts can play a role in the virus' spread by being reservoirs. They include blant night shade (Solanum nigrum), jimsonweed (Datura stramonium) and tomatillo (Physalis ixocarpa).
As with most other tomato viruses, Mellinger says controlling the vectors and the alternative hosts are part of an overall integrated pest management program.