Approach to study of pigeonpea leaf webber [Grapholita critica (Meyr.)] damage dynamics and its relation to weather

Abstract

Investigation of the published data of a field experiment on assessment of damage due to leaf webber (Grapholita critica (Meyr.)Torticidae:Lepidoptera) under seven different sowing periods at weekly intervals between June IV to August II weeks of 2013-14 at Gulbarga (Karnataka) and observations on leaf webber damage recorded on weekly basis between 32 and 42 standard meteorological weeks (SMW) was done to demonstrate appropriate analytical methodology for an improved understanding of seasonal dynamics of G. critica damage and its relation to weather. Approach to analyses included reporting of calendar (SMW) based observations of G. critica damage on crop age basis, one way ANOVA for testing differences in damage levels amongst sowing periods, SMWs and crop age besides description of relations of damage with crop age and weather variables. Seasonal damage levels of G. critica for sowing periods were non-significant but significant (P<0.05) across SMWs and crop age with reduced damage during early and late crop stages irrespective of sowing periods. Seven and four weeks of higher damage and the best fit of polynomial relations of second order in respect of crop age over calendar based periods signified crop stage dependent damage due to G. critica. While MLR revealed significant influence of all weather and crop age variables (R2: 0.79), non-parametric regression revealed that less than 30°C of maximum temperature and greater than 23°C of minimum temperature to be favourable for G. critica damage. Crop age and calendar based observations have their importance for an area wide and field basis management of G. critica respectively.