Population Dynamics of Scirtothrips dorsalis (Hood) Infesting Chilli During Kharif at Dharwad, Karnataka

Abstract

The present investigation was undertaken during two kharif seasons of 2023 and 2024 at Main Agricultural Research Station, UAS Dharwad to assess the population dynamics of chilli thrips. Taxonomic identification results confirmed the species as Scirtothrips dorsalis (Hood). In kharif 2023, thrips incidence started in the 31st Standard Meteorological Week (SMW) and reached a peak of 4.13±0.52 thrips per leaf during the 34th SMW. Whereas, fruit infestation attained its maximum of 2.16±0.42 thrips per fruit at 38th SMW. The similar trend was noticed in kharif 2024, but overall infestation of chilli thrips was lower due to higher rainfall, reduced temperature and increased humidity. Incidence of thrips first occurred on leaf with initial population of 1.13±0.12 per leaf (31st SMW) and reached peak (3.56±0.52 per leaf) in 34th SMW. Natural enemies such as coccinellids, spiders and Orius sp. were associated with thrips incidence. Multiple regression analysis indicated that weather parameters such as maximum temperature, minimum temperature, morning and afternoon relative humidity along with rainfall have influenced 78.5 and 59.3 per cent of the thrips population on leaves and fruits, respectively. Such studies provide a scientific basis for anticipating pest outbreaks and facilitate the development of predictive models for thrips.