Management of Pod fly, Melanagromyza obtusa  on Pigeonpea (Cajanus cajan L.)

Background: Pod fly, Melanagromyza obtusa is one of the most obnoxious pest causing grain damage ranging from 10-80% with a monitory loss of US$ 256 million annually. Being an internal feeder, infested pods do not show any external symptoms of damage until the fully grown maggots chew the pod wall, leaving a thin papery membrane intact called as window, through which adults exit from the pod. Several field studies were conducted to determine the efficacy of insecticides for the control of pod fly. However, these findings did not find acceptability and led to partial success. Insecticides that should leave lesser residues and pose lesser environmental threat have become imperative. The present study aimed to evaluate the efficacy of certain new insecticide molecules against pod fly in pigeonpea ecosystem. 
Methods: Two field experiments were conducted at Regional Agricultural Research Station, Lam, Guntur during Kharif, 2012 and 2013 in a randomized block design (RBD) using pigeonpea cv. ICPL 85063 (Lakshmi) with 17 treatments including untreated control and 3 replications. Two sprays were given at 10 days interval starting from pod initiation stage.  At maturity, number of pods showing pod fly damage were recorded and expressed as percentage. Grain yield was recorded and cost–benefit ratio was worked out. 
Result: Among different insecticides, thiacloprid 21.7 SC, followed by diafenthiuron 50 WP, flubendiamide 480 SC and dimethoate 30 EC were very effective against pod fly with more grain yield and registered highest incremental cost benefit ratio (ICBR). It was further suggested that effective insecticides may be alternated in order to avoid development of resistance to pod fly in pigeonpea.