Population dynamics of aphid and coexisting predators in tomato agroecosystem

Aphids generally attack vegetative plant parts, preferably leaves, and devitalize the plant by sucking the cell sap. Thorough knowledge of pest-predator ecology and their interaction is requisite to initiate timely pest management strategies. Therefore, we aimed to study the population dynamics of aphids and their predators on tomato in Hisar, Haryana during Rabi, 2016-17 and 2017-18. We observed two dominant aphid species viz., Aphis gossypii and Myzus persicae and three aphidophagous predator groups viz., coccinellids, spiders and syrphid fly maggots in the tomato agroecosystem. Aphid infestation started during the 9th standard meteorological week (SMW) and attained a peak during the 12th SMW (22.65 aphids per three leaves per plant). Aphid population exhibited highly significant negative correlation with minimum temperature (r= -0.917**), maximum temperature (r= -0.895**) and wind speed (r= -0.809**). However, it was positively correlated with morning relative humidity (r= 0.933**) and evening relative humidity (r= 0.856**). We used Principal component analysis (PCA) to reduce the dimensions of data and variables were transformed into principal components (PC) to explain the nature and extent of the relationships among different variables. PC1 and PC2 capture 57.6 and 20.3% of the variability in the data, respectively. Aphid predators exhibited a significant positive correlation with the prey population suggesting a positive density-dependent response.