Evaluation of synthetic pyrethroid insecticides for tungro management

Abstract

The five synthetic pyrethroids cypermethrin-1, cypermethrin-2, deltamethrin, fenvalerate and FMC 54800, were evaluated under greenhouse and field conditions to determine their efficacy in preventing tungro infection and in reducing the incidence of tungro disease. Cypermethrin (1 and 2) and deltamethrin killed the vector, Nephotettix virescens, within 7 minutes and prevented tungro infection under greenhouse conditions; the performance of these insecticides was also better under field conditions. Grain yields were higher in plots treated with these insecticides than in the control plot, or in plots treated with other insecticides, in the cultivar Taichung Native 1. In the cultivar Ratna, these insecticides, plus fenvalerate and carbofuran (check insecticide), had an equivalent effect. The vector population in the plots treated with cypermethrin (1 and 2) and deltamethrin was eliminated. There was a negative correlation between the rate of tungro infection and grain yield, and a positive correlation between vector population and disease incidence.