Management of litchi nut borers

The studies on population dynamics and evaluation of insecticides against litchi nut borers (Blastobasis sp. and Gatesclarkeana sp.) were conducted from 2005 to 2007 at Fruit Research Station, Gangian; Research Station, Gurdaspur and Hoshiarpur district (KVK, Bahowal), Punjab Agricultural University, Ludhiana. The borers appeared first on Dehradun 20 days after fruit set (3.6% infested fruits) and caused maximum damage (91.8%) on Calcuttia at fruit harvest. The results on the efficacy of 4 insecticides, viz. fenvalerate (312.5 and 375 g a.i./ha), endosulfan (612.5, 875 and, 1093.5 g a.i/.ha), quinalphos (625 and, 781.5 g a.i./ha) and triazophos (1000 and 1250 g a.i./ha) sprayed twice at fruit set + 20 days thereafter and thrice at fruit set + 20 days thereafter + colour break stage showed that 2 sprays of all the insecticides were significantly less effective compared to their 3 sprays. The effectiveness of the best doses of 4 insecticides at different locations also showed that 3 applications of fenvalerate (375 g a.i./ha), endosulfan (1093.5 g a.i./ha), quinalphos (625 g a.i./ha) and triazophos (1000 g a.i./ha) could be useful in reducing the borer populations on both the varieties in Punjab. The residue analysis of fenvalerate (375 g a.i./ha), endosulfan (1093.5 g a.i./ha), quinalphos (781.5 g a.i./ha) and triazophos (1250 g a.i./ha) at the time of harvest i.e. 20 days after last spray revealed that no residues of any of these insecticides were detected.