Diseases of tomato (
Spotted wilt virus
Tomato spotted wilt virus causes bronzing to blackening of young leaves, necrotic lesions on leaves and stems, and dark streaks often develop along stems and petioles (photo 1). Severe infections cause stunting. Plants look wilted as leaves yellow and droop. Yellow and white rings develop on fruit (photo 2). The virus is transmitted in a persistent manner by thrips, but it is not transmitted from one generation of thrips to the next.
In Arizona, greenhouses located near onion and pepper fields are at risk because thrips are often abundant in onions, and pepper is a common host of the virus. However, the virus has a very wide host range that includes the Solanaceae, Compositae and Leguminosae and may originate from other crops and weeds as well. The virus occurs sporadically in greenhouses or in small gardens where infected transplants have been brought in from outside Arizona.
Control of tomato spotted wilt depends on sanitation, removal of alternate hosts, and avoiding thrips. Chemical control of thrips is not effective in disease control. Infected plants should be removed and disposed of away from the greenhouse. Alternate hosts including weeds and ornamental host plants should be removed from near the greenhouse since they serve as reservoirs for both the virus and thrips.
1 
2 
August 3, 2011