Population Dynamics of Insect Pests of Green Gram [vigna Radiata (linn.) Wilczek] in Semi-arid Region of Rajasthan

Three insect pest species, viz., jassid, Empoasca motti Pruthi; whitefly, Bemisia tabaci (Genn.) and thrips, Caliothrips indicus Bagnall appeared as major insect pests of green gram, Vigna radiata (Linn.) Wilczek in the semi-arid region of Rajasthan. The population commenced from first week of August and remained throughout the crop season in both the years (Kharif, 2006 and 2007). The infestation gradually reached at peak (12.40 jassids, 10.80 whiteflies and 9.40 thrips/ three leaves during Kharif 2006 and 13.2 jassids, 11.20 whiteflies and 9.87 thrips/ three leaves during Kharif, 2007) in the first week of September during both the years. Among natural enemies, the populations of Chrysoperla carnea (Steph.) and Coccinella septempunctata L. were high, whereas, Monomorium indicum (Linn.), Menochilus sexmaculatus (Fab.) and Brumus suturalis Fab. were low. The correlation co-efficient (r) of jassid, whitefly and thrips populations was worked out with weather parameters, viz., maximum and minimum temperature and relative humidity. The data indicated a significant negative correlation of jassid, whitefly and thrips with maximum temperature (r=-0.61, -0.56 and-0.54 in 2006 and -0.65, -0.78 and -0.52 in 2007, respectively) and positive significant correlation of thrips with minimum temperature (r=0.67 in 2006 and 0.56 in 2007, respectively). The data indicated a positive significant correlation of jassid, whitefly and thrips with relative humidity (r=0.62, 0.63 and 0.68 in 2006 and 0.70, 0.56 and 0.72 in 2007, respectively).