G. Anitha and K. Parimala
Abstract
The pod bug, Clavigralla scutellaris Spinola in pigeonpea is an important pest in the semi-arid areas of Andhra Pradesh viz, Mahaboobnagar and Ranga Reddy districts and causes around 15% yield losses. A Platygastrid, Gryon clavigrallae Mineo parasitizes eggs of the bug effectively and hence its conservation is important while formulating the management tactics. Since information about the parasitization efficacy and its dynamics is scant, a study was carried out during rabi seasons of 2010-11 and 2011-12 to observe the extent of its parasitization and its fluctuations as affected by abiotic and biotic factors. Results revealed that parasitization started from the first fortnight of December and reached a peak in the second fortnight of January. It was found to be in the range of 11.3 - 89.5 % in 2010-11 and 10.9 - 88.9% in 2011-12. Correlation and regression studies suggested that mean temperature had a substantial negative effect (r= -0.51) on parasitization, while sunshine hours and host density had a significant positive relationship (r=0.82 and 0.80 respectively). Mean relative humidity, rainfall and wind speed did not influence parasitization Coefficient of determination (r2) was high (0.93) indicating the prominence of abiotic and biotic factors on parasitization by G.clavigrllae. A multiple regression equation was fitted and discussed.