Seasonal Abundance of Major Rice Insect Pests and Natural Enemies in Relation to Weather Parameters in Godavari Delta of Andhra Pradesh

Abstract

Background: Rice insect populations fluctuate considerably with season, crop availability and weather conditions. Aims: The present study aimed to characterise month-wise and season-wise insect abundance, quantify the relative abundance of individual insects, and to determine correlations between insect populations and meteorological variables. Study Design: A total of 156 weekly observations were classified into Rabi (1 December–14 April), Kharif (15 June–30 November) and summer/rice-fallow (15 April–14 June) periods. Descriptive statistics, month-wise and season-wise box-and-whisker plots, relative-abundance analysis, Venn diagrams and Pearson correlation analysis were used to characterise seasonal insect activity and its association with weather. Place and Duration of Study: The present investigation was carried out using weekly light-trap insect catches and weather observations recorded at the Regional Agricultural Research Station (RARS), Maruteru, West Godavari district, Andhra Pradesh, India during 2012–2014. Methodology: Light-trap catches of major rice insect pests and natural enemies, together with weather observations from the Agrometeorological Observatory, were collected daily and compiled by Standard Meteorological Week. Results: Brown planthopper was the dominant pest in all three periods, accounting for 75.22% of the pest catches in Rabi, 47.04% in Kharif and 85.12% during the rice-fallow period. Green leafhopper and white-backed planthopper were particularly important during Kharif, contributing 24.82% and 19.98%, respectively. Green mirid bugs were the dominant beneficial insects during Rabi (99.19%) and Kharif (98.62%), whereas coccinellids contributed a greater share during summer (14.90%). Weather conditions varied strongly among seasons, with summer characterised by the highest temperatures and sunshine, and Kharif by greater rainfall and evening relative humidity. Correlation analysis showed species-specific responses to weather rather than a uniform response of the insect community. Conclusion: These results demonstrate the value of long-term light-trap surveillance combined with weather observations for identifying periods of enhanced pest and natural-enemy activity and for strengthening weather-informed integrated pest management in rice.