Egg mortality of the brown planthopper,Nilaparvata lugens(Homoptera: Delphacidae) and green leafhoppers,Nephotettixspp. (Homoptera: Cicadellidae), on rice in Sri Lanka

Abstract

AbstractRice plants, infested with eggs ofNilaparvata lugens(Stål) orNephotettixspp. in laboratory cultures, were used to trap egg parasitoids in rice fields at two sites over a period of four days in Sri Lanka. Levels of egg parasitism per plant varied from 0 to 54% inN. lugensand 45 to 100% inNephotettixspp. Egg predation was a minor cause of mortality, but attack by a species ofPanstenon(Hymenoptera: Pteromalidae) killed up to 18%Nilaparvata lugenseggs.N. lugenseggs were parasitized byAnagrussp. nrflaveolusWaterhouse,A. optabilis(Perkins) (Hymenoptera: Mymaridae) andOligositasp. (Hymenoptera: Trichogrammatidae).Nephotettixspp. eggs were parasitized by two species ofGonatocerus(Hymenoptera: Mymaridae) and one ofParacentrobia(Hymenoptera: Trichogrammatidae). There was no overlap in field host range between the two parasitoid assemblages.Gonatocerusspp. andParacentrobiaspp. seldom attacked the sameNephotettixsp. egg batch, suggesting the possibility that these species compete in the field. Overall egg parasitism ofNilaparvata lugenswas positively related to host egg density at the spatial scale of the rice plant, but unrelated at the tiller or batch scale.Nephotettixspp. egg parasitism showed a negative density dependent relationship at the spatial scales of the tiller and plant and no relationship at the batch level. The potential role of these egg parasitoids in preventing outbreaks of hopper pests in Sri Lanka is discussed.