Bioassay, Tests of Dipel and Myd-0837 on Leafroller Larvae, 1993

Abstract

Abstract The B. thuringiensis insecticide, Dipel, and a related experimental B. thuringiensis, MYD-0837, were evaluated using a leaf-dip bioassay method for their effect on PLR and OBLR larvae. Treatments were prepared by diluting the appropriate amt of product (see table) in 500 ml water in a glass beaker. A small amt (about 2 u.1) of wetting agent, X-77®, was added to each treatment. An untreated control was prepared using water plus the wetting agent only. Untreated apple leaves were collected from ‘Red Delicious’ trees at the WSU Tree Fruit Research and Extension Center, Wenatchee. Leaves were dipped, then allowed to dry. Two punches (2.3 cm diameter) were taken from each leaf. Four punches were placed in each petri dish (Falcon 1006, 50 × 9 mm). Petri dishes were chosen randomly, and five 1- to 2-d-old leafroller larvae were placed on the leaf disks. The petri dish lids were put in place, and dishes were placed inside a food storage container with a moist paper towel to maintain high humidity and kept at 75°F (±2°F) constant temperature and 16:8 photopervod. Petri dishes were examined after 3 and 7 d and larval survival recorded. Five dishes were used for each treatment (50 larvae per treatment).