Population dynamics of major insect pests of cashew and their associated natural enemies

Abstract

Studies on the population dynamics of major insect pests of cashew and their associated natural enemies were conducted during 2021-22 at Zonal Agricultural and Horticultural Research Station (ZAHRS), Shivamogga, Karnataka, India. During the study, leaf miner, Acrocercops syngramma Meyrick, tea mosquito bug, Helopeltis spp. and thrips, Scirtothrips dorsalis Hood were found to be major pests. Leaf miner was predominant with a peak population of 4.54 larvae per 20 leaves during fourth week of November with highest per cent leaf incidence of 22.70. Tea mosquito bug was found at new flushing and panicle stage with peak activity during second week of December with 6.50 bugs per 20 shoots with peak per cent incidence of 32.75. Thrips occurred both at panicle and nut stage with peak population during third week of February (6.70/20 panicles) and peak per cent incidence on nut surface during first week of April
(33.75 %). There was a positive correlation of leaf miner and tea mosquito bug with minimum temperature, morning relative humidity, evening relative humidity, sunshine hours and negative correlation with maximum temperature and rainfall, whereas thrips showed positive correlation with maximum temperature, sunshine hours and negative correlation with rainfall, minimum temperature, morning relative humidity and evening relative humidity at ZAHRS, Shivamogga. The natural enemies on insect pests of cashew included predators viz., mantidflies, Coccinella transversalis (Fabricius), Chrysoperla sp., red ants, Oecophylla sp. and hover flies, Ischiodon scutellaris (Fabricius).