Impact of Biotic and Abiotic Factors on the Population Dynamics of Mustard Aphid, Lipaphis erysimi (Kalt) on Mustard

The field study investigates the seasonal incidence and population dynamics of the mustard aphid, Lipaphis erysimi (Kalt.), and its natural predator, Coccinella septempunctata Linn., on mustard (Brassica juncea L.) during the Rabi seasons of 2022–23 and 2023–24 at Research Farm of College of Agriculture, Sumerpur. The results revealed that aphid infestation commenced in the last week of December (52nd, SMW) and persisted until mid-March (10th SMW). The aphid population peaked in the 5th Standard Meteorological Weak (SMW) (137.90 aphids per plant) in 2022–23 and in the 6th SMW (138.40 aphids per plant) in 2023–24, coinciding with temperatures ranging from 11.9°C to 25.6°C and moderate relative humidity (36.1%–45.2%). Correlation analysis indicated a significant negative relationship between aphid population and temperature, while relative humidity exhibited a weak positive association. The predatory C. septempunctata population followed a similar trend, peaking in the 5th SMW (9.20 beetles per plant) in 2022–23 and the 6th SMW (9.35 beetles per plant) in 2023–24, with a strong correlation (r > 0.94) between predator and aphid densities. The findings confirm that temperature plays a crucial role in regulating aphid incidence, with higher temperatures (>30°C) leading to a sharp decline in population. The study highlights the potential of C. septempunctata as a biological control agent and emphasizes the importance of integrating weather-based pest forecasting models into sustainable pest management strategies.