Seasonal incidence of mustard aphid (Lipaphis erysimi Kalt.) and its natural enemies in relation to weather parameters under different sowing conditions

Abstract:

A field study was conducted during the Rabi season 2025–26 to investigate the seasonal incidence of Mustard aphid, Lipaphis erysimi (Kalt.) and its associated natural enemies in relation to weather parameters under two different sowing dates. Mustard variety TAM 108-1 was sown on 30^th October 2025 (early) and 30^th November 2025 (late) under non-replicated, pesticide-free conditions. Aphid population was recorded weekly as the number of aphids per 10 cm terminal twig, while ladybird beetles and the parasitoid Diaeretiella rapae (Mummified aphid) were recorded simultaneously. Under the 30^th October sowing, aphid population increased from 1.8 aphid’s/10 cm twig in SMW 50 and reached a maximum of 130.0 aphids/10 cm twig during SMW 4 (26^th January 2026). Under the 30 November sowing, the population increased from 0.8 aphid’s/10 cm twig in SMW 1 and attained a comparatively lower peak of 88.4 aphid’s/10 cm twig during SMW 6 (11^th February 2026). The maximum populations of ladybird beetles were 3.2 and 3.0 beetles/plant, while Mummified aphid populations reached 4.4 and 3.6 parasitoids/10 cm twig under 30^th October and 30^th November sowings, respectively. Pearson correlation analysis revealed a strong positive association of aphid population with ladybird beetles (r = 0.906 and 0.981) and D. rapae (r = 0.926 and 0.959) under the two sowing dates, respectively. Weather variables also showed differential associations with aphid abundance between sowing dates. The findings indicated that sowing time substantially influenced the magnitude and timing of mustard aphid incidence, with the 30^th October sowing experiencing an earlier and higher aphid peak.