Impact of Abiotic and Biotic Parameters on Gryon Clavigrallae Mineo, a Natural Egg Parasite of Clavigralla Scutellaris Spinola

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 dis tricts and causes around 15% yield losses. A Platygastrid, Gnon c/avigrallae 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 po itive 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. c/avigrllae. A multiple regression equation was fitted and discussed.