ABUNDANCE AND FLUCTUATION PATTERN OF INSECT PESTS AND NATURAL ENEMIES IN WINTER BRINJAL PLANT IN SYLHET

ABSTRACT: A field experiment was conducted to study the seasonal incidence and fluctuation pattern of different insect pests and their natural enemies in winter brinjal grown in the experimental farm of Department of Entomology, Sylhet Agricultural University, Sylhet during October 2019 to March 2020. Observation was made in natural condition i.e.; no plant protection measures was taken. The counting of individual arthropod was performed by using visual searching. Eleven arthropod species were observed out of which 6 were insect pests (7 families under 3 orders) and 5 were natural enemies (10 families, 5 orders). The aphid (Aphis gossypii Glover), brinjal shoot and fruit borer (Leucinodes orbonalis Guenee), jassid (Amrasca biguttula biguttula), whitefly (Bemicia tabaci Genn.), epilachna beetle (Epilachna vigintioctopunctata Fab., Epilachna dodecastigma Most.), and leaf roller (Anobata olevacea) were observed as insect pests of brinjal field. Among the natural enemies, ladybird beetles (Micraspis crocera Muls., Menochilus sexmaculatus), spiders (Lycosa pseudoannulata, Oxyopes javanus, Atypena formosana), black ant (Camponotus compressus), dragonflies (Crocothemis servilia) were common. The total number of phytophagous insect was 2508 and their relative abundance was observed as aphid (15.31%) > epilachna beetle (10.06%) > leaf roller (7.39%) > jassid (6.30%) > whitefly (5.05%) > brinjal shoot and fruit borer (0.64%). On the other hand, the total number of all beneficial arthropods were 3093 and their relative abundance was found as ladybird beetle (40.22%) > black ant (10.65%) > dragonfly (1.55%) > spider (1.42%) > preying mantid (1.35%). Consequently, the highest number of Aphid (5.80), epilachna beetle (6.60), leaf roller (3.50), jassid (3.40) and whitefly (3.40) was found at 140 days after transplanting (DAT) on 170 days after sowing (DAS) while binjal shoot and fruit borer (0.45) was found at 130 DAT on 160 DAS. Subsequently, the highest number of ladybird beetle (13.85), black ant (4.0), dragonfly (1.15), spider (0.9) and preying mantid (0.95) was observed at 140 DAT on 170 DAS. Proper knowledge and monitoring of seasonal incidence and fluctuation of pest population and status of natural enemies are essential to manage the insect pest of brinjal. 

Keywords: Seasonal incidence, Solanum melongena, phytophagous pests and beneficial arthropods