Spatio-temporal patterns of black thrips, Thrips parvispinus (Karny) in chilli cultivation: linking climatic variability to pest outbreaks

Present study was conducted during rabi 2023-24 and summer 2024, aimed to elucidate the seasonal population dynamics of T. parvispinus on chilli twigs and their relationship with key weather parameters. During rabi, infestation commenced in November (44^th standard meteorological week [SMW]) at 0.45 thrips per twig and peaked in the 6^th and 7^th SMWs with 9.32 and 9.58 thrips per twig, respectively, before declining by the 8^th SMW. Thrips density exhibited significant positive correlations with maximum temperature (r = 0.61**), afternoon relative humidity (r = 0.09**), and sunshine hours (r = 0.20), but was negatively correlated with minimum temperature (r = -0.68). Floral thrips density similarly showed a positive correlation with maximum temperature (r = 0.62*), indicating that elevated daytime temperatures promote thrips activity during rabi. In summer, infestation began at 7 days after transplanting (10^th SMW) with 1.50 thrips per twig, reaching a peak of 12.15 thrips per twig at 77 days after transplanting (20^th SMW), followed by a gradual decline. Contrary to rabi, summer thrips density negatively correlated with maximum temperature (r = -0.30), afternoon relative humidity (r = -0.24**), and sunshine hours (r = -0.50), but positively correlated with minimum temperature (r = 0.72). Floral thrips density also negatively correlated with maximum temperature (r = -0.26). These contrasting seasonal patterns underscore the complex influence of climatic variables on T. parvispinus population dynamics, reflecting the pest’s adaptation to varying environmental conditions.