Seasonal Incidence and Parasitization of Diaeretiella rapae (McIntosh) on Mustard Aphid, Lipaphis erysimi in Indian mustard (Brassica juncea): A Report from Jobner, Rajasthan

Abstract Mustard aphid, Lipaphis erysimi (Kaltenbach), is a major pest of Indian mustard ( Brassica juncea ) that inflicts significant yield losses under Rajasthan’s semi-arid conditions. Its population dynamics and natural regulation by parasitoids are influenced by prevailing weather factors. The present report was undertaken at Sri Karan Narendra Agriculture University, College of Agriculture, Jobner, Rajasthan, during two consecutive Rabi seasons (2022–23 and 2023–24) to study the seasonal incidence of Lipaphis erysimi and its parasitisation by Diaeretiella rapae (McIntosh) in relation to meteorological parameters. Mustard variety Giriraj was raised under field conditions and weekly observations on aphid density and percent parasitization were recorded. Aphid infestation appeared in late December and early January, reaching peak densities in late January to early February and subsequently declined by March. Parasitization by D. rapae was first recorded in the third week of February during both years, with a peak of 29.62% in the second week of March 2023 and 34.54% in the same period of 2024. Correlation studies revealed a significant positive association of parasitization with maximum and minimum temperatures in 2022–23, while relative humidity showed a significant negative relationship in 2023–24. Rainfall exhibited a non-significant negative association across both years. This report emphasizes the seasonal role of D. rapae as an effective natural enemy of mustard aphid, underscoring its potential utility in integrated pest management programs for mustard cultivation in Rajasthan.