Apple, Control of the Pandemis Leafroller with RH-5992, 1993

Abstract

Abstract An experimental insecticide, RH-5992, was evaluated for its ability to control PLR larvae of the overwintering generation. The test was conducted in an apple orchard near Wenatchee. Trees were 10-yr-old spur-type (‘Oregon Spur II’) on seedling roots. Treatments were applied to three-tree plots replicated five times using a RCB design. All treatments were applied with a handgun sprayer at 300 psi to the point of drip, simulating a dilute spray of approximately 400 gpa. Two rates of RH-5992 plus Lorsban and methyl-parathion were applied at the half-inch green tip (HIG) stage of apple bud development (19 Apr). Two rates of RH-5992 were also applied at the pink stage of apple bud development (5 May). Pre-treatment evaluations were made on 19 Apr by examining 20 fruiting buds per tree and recording the number infested. The post-treatment evaluation was made on 20 May when surviving larvae could be easily located in flower clusters and growing shoots. Each tree was sampled and the number of live PLR larvae recorded. On the first day following the 19 Apr application, five spurs were collected from the middle tree within each replicate of each RH-5992 treatment and the untreated plot (25 total per treatment). Spurs were returned to the laboratory and one was placed in a 2-oz plastic portion cup. One 10-d-old PLR larva reared on artificial diet, usually a third instar, was placed in the cup and the lid put in place. After the 5 May applications, 10 spurs were collected from each RH-5992 treatment and the untreated plot (50 total per treatment). At the same time, PLR larvae were collected from the same orchard where the test was conducted. Spurs were returned to the laboratory, and one was placed in a 2-oz plastic portion cup. One 10-d-old PLR larva reared on artificial diet, usually a third instar, was placed in the cup and the lid put in place. In addition, field-collected leafroller larvae were placed on spurs in plastic cups and handled the same as the laboratory-reared larvae. All larvae were kept at 70°F for 7 d, after which they were examined and the number of live or dead (dead included larvae which were alive but with slipped head capsules) larvae was recorded.