Diseases of tomato (
Curly top disease
Curly top disease is common in Arizona. It is caused by the beet curly top virus (BCTV) or related viruses in the Curtovirus group. Infected symptomatic tomato plants are chlorotic and stunted (photo 1). The leaves are usually thickened and roll upward (giving the disease its name). The virus is transmitted by the beet leafhopper (Circulifer tenellus) which is the only natural vector in North America. The insects can potentially carry the virus throughout their lives (in a persistent manner).
In Arizona BCTV usually occurs in the spring, and it is most prevalent after a wet fall and/or winter when plenty of weed hosts are drying down in the desert and the beet leafhoppers are looking for alternative food sources. BCTV has many strains and a very wide host range. In Arizona it may be problematic sporadically on other hosts such as pepper, spinach, cucurbits and beans. Plants that are susceptible to one strain may be immune to others. Infections have been detected in symptomless hosts also.
Infected plants should be eliminated since they will not recover, but transmission of the virus from plant to plant is dependent on the leaf hopper only. Once the leafhoppers have left, new infections will not occur. There is no control for curly top once plants are affected, but some exclusion or avoidance methods may help. Succession of plantings throughout the season may be a good tactic where disease is common since at least some of the plantings will probably not be infected. Sealed row covers to exclude the leafhoppers from plants may also be effective. Tolerant varieties are being developed, and homeowners should check for local varieties that may have some resistance.
For more information: http://www.ipm.ucdavis.edu/PMG/r783102011.html
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December 12, 2009