Population fluctuation of black cutworm, Agrotis ipsilon (Hufnagel) in chickpea

Abstract

The population trend of black cutworm, Agrotis ipsilon (Hufnagel) and its larval parasitoid, Blepharella lateralis Macquart in chickpea was studied at Regional Agricultural Research Station (RARS), Shillongani, Assam during rabi, 2018-19 and 2019-20. Larval population of A. ipsilon first appeared in the fourth week of November, 2018and second week of December, 2019. The population showed a steady increase and reached a peak (13.80 no. of larvae/sqm and 8.80 no. of larvae/sqm) in third week of January in 2019 and fourth week of January in 2020, respectively. Later it showed a declining trend till harvest. The activity of B. lateralis commenced from the third week of December in 2018 and second week of December in 2019 and continued till the early part of March in both the cropping seasons. The extent of natural parasitism by B. lateralis varied from 2.10-31.20 percent in 2018-19 and 1.20-26.30 percent in 2019-20. Maximum parasitism (31.20 and 26.30 percent) occurred during the fourth week of January in both the study years. The parasitism increased with the increase in population of A. ipsilon larvae and fairly synchronized with the latter’s maximum population. Significant positive correlation was evident between the host population and the parasitism by B. lateralis. Multiple regression analysis also revealed that A. ipsilon population was influenced by B. lateralis. Among the abiotic factors, maximum temperature showed significant negative correlations with the host population. Multiple regression analysis of various abiotic factors with the population of A. ipsilon showed 74.0-83.0 percent relationship with the cutworm population.