Identification and Life Cycle
Tomato spotted wilt is caused by Tomato spotted wilt virus, a member of the genus Tospovirus. Tomato spotted wilt virus has a very broad host range, infecting tomato, pepper, and eggplant and over 1000 plant species in more than 80 plant families. Although Tomato spotted wilt virus can be transmitted mechanically in the laboratory, it is vectored from plant to plant in the field exclusively by several species of thrips. The western flower thrips (Frankliniella occidentalis), onion thrips (Thrips tabaci), and tobacco thrips (F. fusca) are the primary vectors, but at least four other species of thrips can vector Tomato spotted wilt virus. The virus must be acquired by first larval instars, but both larvae and adults transmit the virus after it circulates and replicates in the thrips. Tomato spotted wilt virus and its thrips vectors have very broad host ranges, including many weeds and crops. The virus survives in alternate weed hosts, overwintering crops, contaminated transplants, and its thrips vectors.
Tomato spotted wilt symptoms vary depending on the strain of the virus, host, variety, stage of plant growth at the time of infection, and environmental conditions. If plants are infected when they are young they are stunted throughout the entire season. If infection occurs later in the season, plants exhibit yellow or brown flecks or necrotic rings on leaves, stems, and fruit. In some varieties, flower and leaf drop occurs. Fruit symptoms may appear as yellow or necrotic spots, rings, or mosaic patterns. Tomato spotted wilt can be devastating when infection rates are high and is one of the most damaging viruses infecting tomato, pepper, and eggplant.
Biological Control
No biological control strategies have been developed for tomato spotted wilt.
Plant only high quality transplants known to be free from Tomato spotted wilt virus and its thrips vectors. Control weeds that can serve as alternate hosts in and around tomato, pepper, and eggplant crops. Few resistant or tolerant varieties are available, but should be planted if available. Utilize highly UV-reflective mulches when growing transplants. Apply adequate but not excessive nitrogen fertilizers, which can lead to high thrips populations and Tomato spotted wilt levels.
Control of tomato spotted wilt with insecticides is generally not effective because thrips can transmit Tomato spotted wilt virus before they are killed. Insecticide do slow the secondary spread of Tomato spotted wilt virus and provide some level of disease control.
Categories: Eggplant, Pepper, Tomato, Disease, Tomato Spotted Wilt
Date: 04/01/2007