Damage incidence by Etiella zinckenella in soybean in East Java, Indonesia

Abstract

Damage incidence of physiologically mature soybean by Etiella spp. and Helicoverpa armigera was studied at 100 farmers' field sites in EastJava. Etiella zinckenella and Helicoverpa armigera attacked 9% and 11% ofpods, respectively. Mean seed loss was 12%, which was mainly caused by E. zinckenella. The frequency distribution of E. zinckenella indicated a clumped pattern. Seed loss increased steeply with the date at which crops reached maturity. Seed loss was not influenced by the frequency of insecticide spraying by farmers. Crops with low yields suffered a larger proportion of seed loss than crops with high yields. E. zinckenella oviposited over an extended period during the crop's reproductive stage. The pooled parasitism level of E. zinckenella by a complex of six parasitoids was 15%. Parasitism built up during the study period along with host density, but no evidence of densitydependence was found. Suggestions for future work are discussed. © 1998 Taylor & Francis Group, LLC.