Studies on Biology and Morphometry of an Invasive Insect Pest, Black Flower Thrips, Thrips parvispinus (Karny) in Chilli

Abstract

Chilli (Capsicum annuum L.) is an economically important crop, but its productivity is severely affected by thrips, particularly the emerging invasive species Thrips parvispinus. Limited knowledge of its biology and life cycle necessitates detailed studies to support effective management strategies. The studies on biology of an invasive black flower thrips, Thrips parvispinus (Karny) was carried out at Department of Entomology, College of Agriculture, Vijayapur, University of Agricultural Sciences, Dharwad, under prevailing laboratory conditions of 25-30 °C temperature and 75-80 per cent relative humidity from July to November 2023-24. The female black thrips prefers to oviposit on young leaves and flower buds. The incubation period ranged from 3.55 to 5.30 days. first instar larvae were small and whitish in colour. The first instar larval period was 1.74±0.28 days and it was measured 0.56±0.08 mm in length and 0.17±0.01 mm in width. The second instar larvae were more mobile than the first instar larvae and eat voraciously. The second instar larval period was 3.75±0.44 days and it was measured 1.16±0.19 mm length and 0.26±0.02 mm width. Fully grown second instar larva stopped feeding and moulted to prepupa. Average duration of prepupa was 1.16±0.26 days. Prepupa measured 1.15±0.12 mm length and 0.31±0.02 mm width. The pupal period was 2.099±0.25 days. Pupal stage measured 1.29±0.09 mm length and 0.35±0.02 mm width. The total developmental period was 13.43±1.71 days at 25-30 °C. The longevity of females was 8.46±1.06 days and it was measured 1.60±0.20 mm length and 0.42±0.03 mm width. The longevity of males was 6.51±0.70 days and it was measured 1.38±0.11 mm length and 0.38±0.02 mm width. The number of eggs laid per female during her life time ranged from 34-67 with an average of 51.65±7.52 eggs. The total life cycle of black flower thrips at 25-30 °C was ranged from 16-21 days with an average of 19.03±1.25 days. Adults of T. parvispinus mainly colonize on flowers, whereas nymphs found on the under surface of leaves. Nymphs deeply puncture and scrap the chlorophyll from the underside of the leaf and suck the cell sap as a result corresponding portion on upper side of the leaf looks yellowish to reddish brown. Infested leaves are distorted, curled, lightly mottled and streaked. It gives silvered appearance on old leaves. Adults scraping on petals results in brownish streaks. They also feed on pollen, which results in drying and withering of flower ultimately it is responsible for reducing fruit production. A comprehensive understanding of the biology and behaviour of this insect pest will enhance our comprehension of the interactions between the crop and its environment. This knowledge is crucial for devising effective strategies to manage its population as part of an Integrated Pest Management Program.