Control of yellow stem borer,Scirpophaga incertulas(Lepidoptera: Pyralidae) by mating disruption on rice in India: effect of unnatural pheromone blends and application time on efficacy

Abstract

AbstractSingle applications of slow-release pheromone formulations were used to control yellow stem borer,Scirpophaga incertulasWalker, by mating disruption in two trials on rice in India. The first trial compared the efficacy of two formulations containing 1:10:1 and 1:10:0 ratios of (Z)-9-hexadecenal, (Z)-ll-hexadecenal and (Z)-9-octadecenal, components of theS. incertulaspheromone, and a commercially-available formulation, Selibate CS, containing the relatedChilo suppressalisWalker pheromone, a 1:10:1 blend of (Z)-9-hexadecenal, (Z)-ll-hexadecenal and (Z)-13-octadecenal, with farmers' practice plots treated with insecticides. Pheromone trap catches indicated that in each of the pheromone-treated plots the catches of male moths were reduced by up to 98% compared with catches in the insecticide-treated plots suggesting that pheromone-mediated communication was disrupted. Larval damage ranged from 5.7 to 8.1% white heads (WH) in the insecticide-treated plots compared to a significantly reduced range of 2.1 to 2.4% WH in the pheromone-treated plots. There was no significant difference between the damage estimates recorded for each of the different pheromone treatments. A second trial compared the effect on efficacy of applying the two-component pheromone formulation on different dates, 9–12 and 39–44 days after transplanting. Both pheromone treatments gave significantly lower levels of WH damage compared to equivalent insecticide treated plots; 1.8, 2.0, and 6% respectively. In both trials rice grain yields increased by between 5 and 12% in pheromone-treated plots compared to insecticide treated plots, which was due, at least in part, to the cumulative effect of reduced stem borer damage in both the tillering and reproductive stages of the crop cycle. The formulations exhibited pseudo-zero order release rates with field lives of between 70 and 90 days.