EXPLORING THE ABUNDANCE AND DIVERSITY OF INSECT PESTS ON BORO AND AMAN RICE IN SYLHET

Abstract

The study was conducted to explore the abundance and diversity of insect pests dwelling in boro and aman rice fields, Shahparan, Sylhet during the period from November 2013 to April 2014 in boro rice season and May to November 2014 in aman rice season. The results revealed that 16 and 14 different insect pest species were found in boro and aman rice fields, respectively. The relative abundance of rice green leafhopper (GLH) was highest in both the seasons. The highest incidence of insect pest was observed in boro season. The average occurrence of insect pests was higher at tillering stage (55 days after transplanting, DAT) and lower at seedling stage (15 days after sowing, DAS) in two seasons. The Diversity Indices of insect pests varied among the Order groups and feeding habits in two seasons. Shannon's Diversity Index (H) and Margalef's Index of insect pest richness were found highest in boro rice whereas, Pielou's Evenness (J) of insect pests was found highest in aman rice. The Order Lepidoptera exhibited highest diversity and the order Coleoptera exhibited lowest diversity in respect of Shannon's Index (H), Evenness (J) and Richness (M.I.) for both the seasons. On the other hand, Shannon's Diversity Index (H) and Pielou's Evenness (J) were found highest in case of defoliators and stem sucker pests in both the seasons whereas, Margalef's Index of richness was found highest in boro season in case of defoliators. The abundance of insect pest species between two seasons ranked as Boro > Aman. The abundance of insect pest species among the Orders ranked as Hemiptera > Lepidoptera > Orthoptera > Coleoptera in boro season and Hemiptera > Orthoptera > Lepidoptera > Coleoptera in aman season.