Citrus Cutworm Pesticide Efficacy Trials, 1995

Three formulations of Bacillus thuringiensis for the control of citrus cutworm were evaluated on 30 yr old ‘Washington navel’ orange trees at Exeter Farms, Exeter, California. There were five treatments in the experiment including! an untreated control, ABG 6405, two rates of Dipel ES, and Dipel ES/NT. The insecticides were applied on 21 Apr with an FMC CP-267 speed-sprayer pulled behind a tractor using 200 gpa (outside coverage). The experiment was divided into 15 plots. Each plot was 3 rows wide and 15 trees in length.; The five treatments were assigned based on pretreatment sampling of larvae and replicated 3 times. Six trees inside the center row of each plot were designated as sample trees. Larval collections were accomplished by placing a canvas beating sheet (112 cm X 75 cm) beneath the outside foliage of the sample trees and vigorously shaking the foliage. Citrus cutworm larvae which fell onto the canvas were counted and recorded by instar, then returned to the foliage. Pretreatment larval counts were made on 13 Apr by sampling the northeast and southwest quadrants of each tree. Post treatment counts were made on 9 May by sampling all four quadrants of each sample tree, again recording each instar. Percentage of fruit scarred by citrus cutworm was evaluated on 10 Aug on each of the sample trees within a 2 meter vertical swath around the tree beginning approximately 20 cm above ground level and extending approximately 40 cm into the tree interior. In 1995, late Apr and early May temperatures in Exeter ranged from relatively cool to warm, with daily maximums between 52°F and 86°F (mean of 72°F). Precipitation occurred on 13 Apr (0.24 inch), 16 Apr (0.28), 17 Apr (0.16), 18 Apr (0.24), 29 Apr (0.16), 1 May (0.71), and 4 May (0.20).