Seasonal Incidence of Insect Pests and Their Biocontrol Agents on Soybean

Abstract

Seasonal incidence of insect pests of soybean will be recorded from field during kharif 2010.Soybean variety JS-93-05 will be sown on 3 July 2010. In this experiment numbers of plants infested by girdle beetle and the number of caterpillar pests and natural enemies will be counted from ten randomly selected places (in one meter row-length ). to record the observations on sucking pests, insect population will be recorded from randomly selected twenty plants on which five leaves taken three from upper and two from bottom in each at ten days interval. During the course of study, five insects species, viz., Girdle beetle, Obereopsis brevis tobacco caterpillar, Spodoptera litura, green semilooper, Chryrodecxis acuta, Jassids, Empoasca kerri and white flies, Bemisia tabaci were recorded as the major pests on soybean, variety JS 93-05 causing damage at various stages of the crop. All these insects made their first appearance on the crop to a greater or lesser extent in the last week of July. The activity of girdle beetle increased gradually with peak density of the cerambycid in the last week of August recoding 3.2 damaged plants per meter row with seasonal mean of 1.73 damaged plants. The density of lepidopterous caterpillars increased gradually with peak population of 5.0 larvae per meter row during the last week of August and seasonal mean of 3.22 larvae per meter row among the sucking pests, whitefly was observed in higher numbers than jassids. The peak density of sucking pests was observed during third week of September with 4.4 sucking pests/plant and seasonal mean of 3.62 white flies and jassids per plant. Preying upon the sucking Insects, were two species of lady bird beetle, Coccinella septumpunctata and Menochilus sexmaculata and two species of spiders, lynx spider and an unidentified golden preying spider. The latter was also a recorded preying on lepidopterous larvae. A predatory pentatomid bug, Eocanthecona furcellata was observed sucking the body sap of lepidopterous larvae, there existed a positive but nonsignificant correlation between lepidopterous larvae and predators and between sucking pests and predatory fauna with „r‟ values 0.545 and 0.798, respectively. (