Field evaluation of spinetoram 12 SC against Maruca vitrata on pigeonpea

Abstract

The acute and persistent toxicity experiments was conducted in the Insectary of Agricultural College and Research Institute (ACandRI), Maduari, Tamil Nadu Agricultural University. Two field experiments were conducted at farmer’s field at Jadhi Goundanpatti, Attur Block, Dindigul district, Tamil Nadu. The incidence of M. vitrata (Geyer) has been increasing for the last few years and the larvae bore inside the flower buds, flowers and the green pods and cause upto 40-70 per cent damage. A new biological insecticide molecule, spinetoram 12 SC was evaluated for acute toxicity on laboratory reared M. vitrata population, and persistence on pigeonpea leaves at laboratory conditions; and effect on M. vitrata on pigeonpea at field conditions during 2012-13 and 2013-2014 seasons. Acute toxicity studies revealed that LC50‘s of spinetoram on third instar larvae after 24, 48 and 72 hours after treatment were 4.30, 1.95 and 1.46 ppm respectively. In persistence studies, Persistence was upto 11 DAT for spinetoram 12 SC 27 g a.i./ha, spinosad 45 SC 78 g, emamectin benzoate 5 SG at 11 g a.i./ha, and monocrotophos 36 SL at 500 g; and 14 DAT for spinetoram 12 SC 36 and 45 g a.i./ha. There was a reduction in the mortality of M. vitrata larvae as the time increased and there was no mortality at 21 DAT. Results indicated that spinetoram 12 SC was significantly effective at 36 and 45 g a.i./ha when sprayed thrice at 15 days interval and minimized the incidence of leaf feeder, M. vitrata on pigeonpea plants.