Seasonal Activities of Thrips (Thrips tabaci Lindeman.) in Onion and Their Relation with the Various Environmental Factors

Aim: To study the population dynamics of thrips (Thrips tabaci Lindeman) infesting onion in relation to weather parameters Study Design: Field trail; Randomized Block Design. Place and Duration of Study: The study was conducted at College farm at Navsari Agricultural University (NAU) Southern Gujarat, INDIA during Rabi of 2022-23 and 2023-24. Methodology: For observations of thrips (Thrips tabaci Lindeman), the whole experimental plot was divided in five sectors and 5 plants were randomly selected from each sector. The observations on absolute thrips population were recorded at weekly interval by counting the number of thrips per plant during morning hours starting from one week after transplanting till to harvesting of the crop. Results: Thrips population initiated during 3rd week of December (51st Standard Meteriological Week) during both the year in the range of 2.25 to 15.87, 1.60 to 24.50 and 2.51 to 18.85 thrips per plant with an average of 6.67, 10.54 and 8.60 per plant during 2022, 2023 and in average of two years. The highest peak (15.87 /plant) was observed during 3rd week of February (8th Standard Meteriological Week) in 2022 whereas, during 4th week of February (9th Standard Meteriological Week) in 2023 as well as in average of two years with a population of 24.50 and 18.85 per plant, respectively. Thrips population had highly significant positive correlation with MaxT (r=0.678) whereas, highly significantly negatively correlated with Evening Relative Humidity (r = -0.727) during 2022. The population of thrips highly significantly positively correlated with Bright Sunshine Hours (r=0.672) during 2023. The other weather parameters had no role on incidence of thrips as the results were non-significant. Conclusion: results of population dynamics of thrips (Thrips tabaci) on Onion for both the years, it can be concluded that the infestation of thrips was higher during 5th week of January to 1st week of March on onion.