Seasonal Activity of Pod Fly, Melanagromyza Obtusa (Malloch.) (Diptera: Agromyzidae) and Effect of Abiotic Factors on Its Incidence in Pigeon Pea

A field experiment was carried out during rainy season of 2003 and 2004 at the research farm of Project Directorate Cropping System Research (PDCSR), Modipuruam, Meerut, Uttar Pradesh for development of early prediction system to optimize the application of insecticides for management of pod fly Melanagromyza obtusa (Malloch) in pigeon pea. Maggots were first observed in first week of October (90–100 days old crop) and peaked up to 47^th week i.e. in first week of November when crop was 100 to 125 days old and thereafter population declined to zero level with maturity in the first week of December, and pest remains active for nearly two months. The maggot population started building up when the maximum temperature dropped below 32° C and attained the peak when it further declined. The present findings suggest that maximum temperature below 30° C and minimum temperature between 8.1–17.0°C and average relative humidity around 60–70% is conducive for population build up of the pest. Correlation between maggot population and rainfall for current, one, two and three weeks before was found significant and negative indicating adverse effect of rainfall. A prediction equation using current week data prepared by stepwise multiple regression analysis revealed 0.48 R² value and considered as best fit for predicting population of pod fly, M. obtusa.