ABUNDANCE AND DIVERSITY OF INSECT PESTS ATTACKING MAIZE (ZEA MAYS) IN SYLHET DISTRICT OF BANGLADESH

ABSTRACT: Maize (Zea mays), a globally significant crop, is increasingly cultivated in Sylhet district of Bangladesh, but faces challenges due to various insect pests. This study aimed to record the abundance and diversity of insect pests of maize field in Sylhet district. Field studies were conducted at Jalalabad Union of Sylhet Sadar Upazila under Sylhet district, from January to May 2022. Results revealed that various insect pests and natural enemies were found in the maize field viz., cutworm, fall armyworm, tachinid fly, non-biting midge, ladybird beetle, honey bee, and grasshopper. Among these insect pests, non-biting midge (Chironomus sp.) (51%) and fall armyworm (Spodoptera frugiperda) (16%) were identified as the most prevalent. Insect pests and natural enemies varied by functional diversity with 51% categorized as neutral, 30% as pests, 10% as predators, 5% as parasitoids and 4% as pollinators. The abundance and diversity of insect pests belongs to five different orders which include Diptera (56%), Lepidoptera (24%), Coleoptera (10%), Orthoptera (6%), and Hymenoptera (4%). The Shannon-Wiener Diversity Index was 1.74, indicating a stable community structure, and Pielou’s Evenness Index was 0.275, suggesting moderate species distribution uniformity. Insect abundance differed across maize growth stages, with certain pests prevalent in specific stages: cutworm was found during the seedling stage; non-biting midge and ladybird beetle were observed from seedling to harvest; fall armyworm, tachinid fly, and grasshopper were present in both vegetative and reproductive stages; and honey bee appeared during the reproductive stage. Temperature and relative humidity were found to have distinct effects on insect populations, with correlations varying among different species. Temperature was positively correlated with non biting midge (r = 0.86), fall armyworm (r = 0.54), and tachinid fly (r = 0.39), while negative correlations were observed with ladybird beetle (r = -0.05) and grasshopper (r = -0.31). In terms of relative humidity, positive correlations were identified for fall armyworm (r = 0.14), ladybird beetle (r = 0.31), grasshopper (r = 0.64), and tachinid f ly (r = 0.07), whereas non-biting midge showed a negative correlation (r = -0.12). These findings would be helpful for implementing IPM program to manage these pests effectively and ensure sustainable maize cultivation. 

Keywords: Maize insects, insect diversity, abundance, IPM, Sylhet, Correlation, Temperature, Humidity