Impact of Weather Parameters on Population Fluctuation of Chilli Thrips, Scirtothrips dorsalis Hood

Abstract

Chilli var. Tejaswini was grown in three quadrates (5.0×6.0 m²) during pre-kharif season (January-June) of 2018 and 2019 at farmer’s field, Sriniketan, West Bengal, India to study the fluctuation of thrips population during the crop growing seasons under the influence of varying weather parameters. Population fluctuation of the thrips was recorded at weekly intervals starting from one week after transplanting till the last harvest. The insect first appeared on 6-8 leaves stages of the crop during both seasons and the population gradually reached to peak  at 14 MSW (10.95 thrips leaf^-1) and 13 MSW (9.83 thrips leaf^-1) during 1^st and 2^nd seasons, respectively. Correlation of thrips population with both previous and same meteorological standard week data showed different results. Significant negative correlation with relative humidity (r=-0.561^*) but positive with sunshine hours (r=0.476^*) recorded only during 2018 when correlations were studied with previous week weather data. Studies on multiple regression revealed that combined effect of weather parameters on the population build up of thrips had 26.0% (R²= 0.260) and 55.4% (R²=0.554) during 1^st season while it was 40.6% (R²=0.406) and 18.9% (R²=0.189) during the 2^nd season. Trend analysis revealed that during 1^st season maximum and minimum temperatures around 35.0°C and 20°C found favourable for pest population build-up, while relative humidity (65% or higher), rainfall (6.0 mm), and bright sunshine (8 h) negatively affected the thrips population. A similar trend in insect population build-up was also recorded during the 2^nd season.