Apple, Laboratory Evaluation of Penncap M for Control of Larvae of Rblr, 1991

Abstract

Abstract Redbanded leafroller (RBLR) larvae caused serious damage to fruit in Frederick County, Virginia, in 1990. In one orchard where Penncap M had been used for several years (including 1990) the problem was particularly severe and larvae from eggs laid by the overwintering generation were very abundant in the spring of 1991. Efficacy of insecticide against RBLR larvae in this orchard was questioned. Consequently, two laboratory toxicity studies were conducted. Exp. 1 was designed to evaluate relative toxicities of several pesticides currently recommended for control of RBLR. Exp. 2 was performed to determine an effective dosage of pesticides for grower use. Terminal apple shoots bearing 5 live RBLR larvae were dipped in the appropriate toxicant dilutions which had been mixed in 1 gal battery jars. There were 4 replicates of each treatment and a control. After dipping, the basal portion of the shoot was passed through a fine meshed nylon screen into water in the bottom of a styrofoam cup. The screen was taped so as to seal it to the top of the cup and served to prevent larvae from entering the water. Each of these units was then placed in a clean glass battery jar. Tops of jars were covered with fine nylon netting, held in place with a rubber band, and held at 80°F in a lighted room. Larvae were examined after 24 and 48 h and categorized as live or dead. Death was determined by the lack of any movement when the larva was probed gently with a blunt steel probe.