Seasonal Incidence of Major Insect Pests of Groundnut and Their Natural Enemies in Relation to Meteorological Parameters

Abstract

Seasonal incidence of major insect pests in groundnut was studied during kharif 2015-16 with the variety, Kadiri-6 (K6). The results indicated that the population of groundnut leaf miner (Aproaerema modicella) reached peak in the first week of September with a mean larval incidence of 0.8 plant-1 and the larval population of tobacco caterpillar (Spodopter alitura) was more abundant on the crop during second week of October with a mean incidence of 9.3 plant-1. Aphid (Aphis craccivora) touched the peak in the first week of September with a mean population of 8.8 aphids top 2 cm shoot-1; whereas, leaf hopper(Empoasca kerri) attained the peak in the second week of September with a mean population of 10.6 three leaves-1 plant-1. Maximum activity of thrips, Scirtothrips dorsalis (Hood) was recorded in the second week of October with a mean of 4.8 terminal-1. Leaf miner, leafhopper and aphids showed positive correlation with rainfall (r= 0.120, 0.158 and 0.121, respectively). In case of larval (r= -0.075) and adult (r= -0.103) populations of S. litura, adult catch of H. armigera (r= - 0.299) and thrips (r= -0.105) negative correlation were observed with rainfall. Larval and adult populations of S. litura and thrips showed positive correlation to both minimum (r=0.196, 0.159, 0.179) and maximum temperature (r=0.067, 0.266, 0.095, respectively). However, leaf miner, leafhopper, aphid populations and H. armigera adult catch showed negative correlation for maximum temperature (r= -0.008, -0.250, -0.014 and -0.148) and positive correlation with minimum temperature (r= 0.084, 0.663, 0.646 and 0.127, respectively). With respect to relative humidity, all the pest populations have showed negative correlation, however, leaf hopper and aphids only recorded significance at 5% with morning RH (r= -0.680 and -0.583). Peak activity of predators were recorded a week after the pest populations attained their peak.The populations of three predators’viz., coccinellids, spiders and syrphid fly maggots were positively correlated with all the pest populations