Thrips management in processing tomatoes and influence on Tomato spotted wilt virus symptom incidence in Central California

T.A. Turini, M. LeStrange, R.L. Gilbertson
Tomato spotted wilt virus (TSWV) is responsible for substantial economic damage in processing tomatoes in Central California. The primary vector in this region is the Western flower thrip, Frankliniella occidentalis, which is difficult to control. A program was developed in which genetic resistance, sanitation and site selection were utilized to minimize the economic impact of the virus in this production area. To address the question of the utility of insecticides as a management tool for this disease, efficacy of insecticides was compared in trails conducted from 2007 to 2012 and insecticide programs were evaluated in trials conducted from 2009 to 2012 and in 2015. In the insecticide efficacy experiments, seven to 12 materials were compared annually. Thrip population densities were quantified by nymph and adult counts per 25 flower samples that were collected 3-5 days after application. In the insecticide program comparisons, the experimental design was a split plot with four replications. Main plot treatments consisted of materials injected through the drip irrigation system at different timings and an untreated control. Subplot treatments were rotations of foliar-applied insecticides, which were spinetoram and dimethoate rotations applied two or five times during the season. Also, during four of the seasons, cyantraniliprole was applied as a transplant drench 24 h before planting. TSWV-symptomatic plants were quantified per plot two or three times during the season and the percentage of TSWV incidence was recorded. The materials that consistently provided control over multiple seasons were spinetoram, methomyl and dimethoate. Reductions of TSWV incidence were associated with foliar applications in three of four trials, and cyantraniliprole drenches reduced incidence in two of the four trials. The drip-injected insecticides did not result in lower levels of TSWV compared with the untreated control. Under extremely high TSWV pressure, insecticides efficacious against thrips may not reduce levels of TSWV, as in 2010. However, prudently timed, effective insecticides can reduce the potential disease incidence or delay onset, thereby reducing the level of damage in combination with other management approaches.
Turini, T.A., LeStrange, M. and Gilbertson, R.L. (2017). Thrips management in processing tomatoes and influence on Tomato spotted wilt virus symptom incidence in Central California. Acta Hortic. 1159, 117-124
DOI: 10.17660/ActaHortic.2017.1159.18
Solanum lycopersicum, tospovirus, Western flower thrips, Frankliniella occidentalis, insecticidal vector control, symptom expression

Acta Horticulturae