Effects of Atmospheric Deposition on Efficacy Of Pesticides for Elm Leaf Beetle Control, Delaware, Co., Oh., 1985

Abstract

Abstract One-year-old potted elm, Ulmus spp., cuttings were sprayed with insecticides and subjected to a combination of atmospheric pollutants and acid rain treatments to determine if insecticidal efficacies against elm leaf beetle adults were affected. The experiment was a factorial design. The factors were 3 insecticides (Dursban, Mavrik Aquaflow, Sevin XLR) applied at recommended rates; 2 simulated acid rain (SAR) treatments (4.0 pH, ambient); 2 elm cultivars ('Homestead,' 'Pioneer'); 3 atmospheric pollutant treatments (0.1 ppm 03, 0.2 ppm S02 plus 0.1 ppm 03, ambient); and 3 to 6 replicates each. Fumigations were in 4 open-top chambers ca. 3 m in diam and 2.5 m in height. SAR solutions were made by adjusting the pH of deionized water with 2 parts H2S04 and 1 part HN03. SAR was applied through beta fog nozzles at 69 kPa in chambers equipped with platforms, 1.2 m in diam, revolving at 4 rpm. Weekly SAR and fumigation treatments began 13 Jun. These treatments were 45 min (1.27 cm) SAR followed by fumigation for 5 days at 7 h/day. Elms that were ttt treated with insecticides, fumigants or SAR served as controls. Cuttings were sprayed to runoff on 8 Jul (32°C, 62% RH, winds calm) using a 11.4-liter c impressed C02 driven R&D Model TS backpack sprayer equipped with a no. 5500 adjustable cone tip nozzle opened Vi turn from full closed at 206.8 kPa pressure. At 10 days postspray (Trial l)and at 37 Days postspray (Trial 2), insecticide efficacy was assessed by placing 5 or 10 elm leaf beetle adults in petri dishes with foliage from the different treatments. In Trial 1, foliage from 4 to 6 trees was used per treatment combination. In Trial 2, foliage from 6 trees was used per treatment combination (3 'Homestead' plus 3 'Pioneer'). Percent beetle mortality was determined in each petri dish after 48 h. Data were 3 lbjected to an angular transformation and analyzed by a 3 factor ANOVA at the 5% level. Where significant differences occurred, ANOVA was followed by an SNK multiple comparison test at the 5% level.