Irish Potato, Control of Potato Infesting Aphids, 1987

Abstract

Abstract The experiments with fohar and systemic insecticides were randomized complete block designs with 6 replicates each and were conducted at Presque Isle, Maine, on land that was in clover in 1986. The potato planting dates were 20 May for the systemic insecticide experiment and 18 May for the foliar insecticide experiment. In each experiment the 3.0-m space between blocks and the 1.4-m space between columns and at the sides and ends of the experiments was sown to oats after planting. Each plot consisted of 4 rows of potatoes, each row 0.9 m apart and 15.0 m long. The healthy Katahdin seed pieces (75 g each) were planted with a tractor-pulled, assisted-feed planter. Fertilizer and hilling practices were normal for the area. Late blight was controlled by 7 foliar applications of Dithane F-45 (2338 ml/ha the weeks of 6 and 13 Jul; 2806 ml/ha the weeks of 20 and 27 Jul and 3, 10, and 17 Aug). Side-dress applications of insecticides were made by hand with a plastic tube applying previously weighed amounts of insecticide. Measured amounts of insecticide were applied on each seedpiece for the seedpiece treatments. Foliar insecticide applications were made with a Century boom sprayer, 3 nozzles/row at 7.0 kg/cm2 pressure and 0.95 kl/ha. Numbers of aphids (by species) were counted on top, middle, and bottom leaves of 25 plants in the middle rows of each plot. When dates of count and application were the same, aphid counts were made prior to applications of the insecticide. Analyses of variance were calculated following transformation of the data using logI0(i + 1). Means of the total number of wingless aphids were compared using DMRT and then reconverted. The soil was classified as Caribou loam, pH 5.2. Total monthly rainfall for June, July, and August was 8.8, 7.6, and 4.4 cm, respectively. The average temperature for each of the same 3 months was 16.5, 19.0 and 19.1°C.