Influence of Weather Factors and Planting Dates on the Population Fluctuation of Thrips tabaci in Onion Fields in Egypt

Abstract

Climate change poses significant challenges to insect populations, and natural enemies and greatly impacts their interaction with host crops. In onion production, Thrips tabaci has become a serious threat influencing quality and yield. Therefore, the present study aimed to investigate the distribution of T. tabaci on onions (Giza 20 variety) planted in three different dates during 2021/2022 and 2022/2023 growing seasons. Results obtained revealed that thrips population showed four peaks on the 1^st planting date, the 1^st peak with an average population density of 677.21 and 703.24 individuals/plant in the two seasons, respectively), followed by the 2^nd peak with 500.05 and 602.13 insects/plant, in the two seasons, respectively. Meanwhile, the 3^rd planting date had two peaks (385.77 and 494.04 individuals/plant). The first appearance of thrips was observed on the 4^th week of December, 1^st week of January, and 3^rd week of January with 15.3, 14.85 & 11.39 thrips/plant per week, in the 1^st, 2^nd and 3^th planting dates, respectively, during the first season 2021/2022. There was a correlation between the T. tabaci numbers and temperature, relative humidity, plant age in both seasons. The interaction between plant age, natural enemies, weather conditions, and thrips population density resulted in a strong relationship affecting onion yield. Delaying planting until December reduced pest pressure, offering a practical strategy for farmers. Furthermore, maintaining adequate populations of natural enemies enhanced biological control efficacy.

Keywords:

Onion, weather factors, agricultural practices, Thrips tabaci.