INSECT PESTS AND THEIR DAMAGE PATTERNS IN PADDY (Oryza sativa L.) IN SAPTARI DISTRICT, NEPAL

Abstract

This study focused on to identify insect pests and their damage patterns studies were conducted in two varieties of paddy plots in Gadhiya Village of Rajbiraj Municipality during rice growing season of 2019. Sampling field visits consist of three stages, starting from the vegetative growth stage, flowering stage and maturity (ripening) stages of the paddy growth stage during different time periods of a day. Two sampling methods were used, i.e. swinging a sweep net and ocular observation for insect pests collecting purposes. The sampling was done three periods of a day i.e. morning, afternoon and evening. This study composition recorded 14 insect pest species were founded that belongs to 12 families of eight orders found in paddy field. Hieroglyphus banian was the dominant species among all stages, followed by Nilaparvata lugens, Leptocorisa acuta, Dicladispa armigera, Cnaphalocrosis medinalis, Stenchaetothrips bioformis, Spodoptera mauritia pests were found in both varieties of paddy plant. Rice pest abundance shown in the field, a high relative abundance of Orthoptera (32.8%) pests was found, followed by Homoptera (19.1%), Hemiptera (15%), Heteroptera (12.9%), Lepidoptera (10.1%), Coleoptera (7.1%), Thysanoptera (1.9%) and Diptera (1.1%). For the total sampling period, the biological indices calculated consist of the Shannon-Wiener diversity index (H’) is 2.43, Pileou’s evenness index (J’) is 0.92 in a SM variety whereas the value of H’=1.29 and J’=0.72 in JM variety. The study identified six damage patterns on the crop (leaf cutter or miner, stem borer, immature grains milk sucker, leaf roller, sapsucker, panicle cutter). Most of them (11) species were responsible for leaf-cutting or mining of the leaf blade and less (two) species were leaf rollers. Results indicated that diversity of insect pests was found more in paddy field cultivated ensured a good balance between the populations of pests and damage patterns for better paddy development. However, the periodic abundance was seen more in the afternoon than evening and morning. Diversified of insects can be potentially effective to conserve, use and promote biodiversity which helps for sustainable food security by yielding more productivity from the agricultural ecosystem in Saptari.