Some Parasitoids of Rice Pests Collected from Insecticide-Free Rice Fields in Sri Lanka

Abstract

Insect pest problem in rice have become much more frequent and complexes in the last three decades mainly due to the expansion of growing areas over time and space. Continuous availability of food source helps pests to multiply rapidly. Naturally occurring parasitoids of rice pest play a key role in suppressing the pest population in considerable level. Evaluation of biology and population dynamics of parasitoids in rice eco-systems is a prerequisite to implement biological control programs. Therefore, Eggs, larval, pupal and adult parasitoids were collected in four pesticide free paddy fields i.e, Batalagoda, Kuliyapitiya, Narammala and Madampe in agro-ecological zone IL la of Sri Lanka. Collected specimens were preserved in ethanol (70% ) and morphological characters were examined under the dissection microscope. The specimens were identified using published keys and identified species were illustrated. Nine species of parasitoids belonging to Order Hymenoptera and Diptera were collected during the survey. Hymenopteran wasps were belonged to family Ichneumonidae i.e. Amauromorpha accepta schoenobii (Viereck), Xanthopimpla flavolineata (Cameron), Charops bicolour (Szepligeti); Braconidae, i.e. Stenobracon nicevillei (Bingham), and Scelionidae, i.e. Gryon nixoni. Both Dipteran parasitoids were belonged to family Tachinidae. Composition of parasitoid community was varied in different localities of the agro-ecological zone showing highest diversity in Batalagoda area. Gryon nixoni (Masner) was found to be the most abundant parasitoid species and parasitism was highest (54 % ) in Narammala area. Further investigations are needed to find the potential use of identified parasitoids in conservation and mass rearing program in rice fields.