AbstractControl of yellow stem borer, Scirpophaga incertulas (Walker), in rice was attempted by mating disruption using the natural ratio of pheromone components, a 1:3 blend of (Z)-9- and (Z)-11-hexadecenal, in replicated trials at three locations in Andhra Pradesh, India, during the 1994 and 1995 dry seasons. The pheromone was formulated in SelibateR and applied by hand at a rate of 40 g a.i./ha. In Medchal and Nellore, pheromone-mediated communication was reduced by at least 94% for the first 50 and 64 days after application respectively, as measured by pheromone trap catch suppression. Compared with adjacent farmers' practice plots, subsequent dead heart and white head damage were reduced by 74 and 63% and 83 and 40% in Medchal and Nellore, respectively. In Medchal, average rice yields were increased compared to the farmers' practice plots, 4108 and 3835 kg/ha respectively, but in Nellore, they were the same as those obtained in the farmers' practice plots, 6400 and 6733 kg/ha respectively. In Warangal, the level of communication disruption over the first 70 nights after pheromone application was less than obtained in either Medchal or Nellore and averaged between 50 and 87%. The maximum dead heart and white head damage recorded in the pheromone-treated plots in Warangal were 2.8 and 15.7% respectively compared to 7.0 and 20.9% respectively in the farmers' practice plots. Differences in S. incertulas larval damage estimates obtained from the pheromone-treated and farmers' practice plots in Warangal were reflected in grain yields, 4036 and 3715 kg'ha respectively. Surveys of insecticide use indicated that 92% of smallholders in Medchal applied insecticide at least once per season while in Warangal over 60% applied insecticide on two or more occasions. The data show that season-long control of S. incertulas comparable to that obtained with conventional insecticides can be achieved by mating disruption in smallholder rice fields in India.
Egg Mass Density Dependent Parasitoids of Rice Yellow Stem Borer, Scirpophaga incertulas (Walker) (Lepidoptera: Pyralidae)
