Irish Potato, Control of Potato Infesting Aphids, 1985

Abstract

Abstract The foliar and systemic experiments were randomized complete block designs with 6 replicates each and were conducted at Presque Isle, ME on land that was in clover in 1984. The planting dates were 21 May ’85 for the systemic experiment and 22 May, for the foliar experiment. In each experiment the 3-m space between blocks and the 1.4-m space between columns and at the sides and ends of the experiments were sown to oats after planting. Each plot consisted of 4 rows of potatoes 0.9 m apart and 15.0 m long. The healthy Katahdin seed pieces ca. 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 M-45 (1681 g/ha weeks of 8 and 15 Jul, 2242 g/ha weeks of 22, 29 Jul, 12, 19 and 26 Aug) and 1 application of Ridomil 2E (1.17 1/ha 31 Jul). Soil applications of insecticides were made with a modified Gandy applicator just prior to planting or as a sidedressing after emergence. Foliar insecticide applications were made with a Century boom sprayer, 3 nozzles per row at 7.0 kg/cm2 pressure and 1.2 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 log10(x + 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 rain fall for Jun, Jul, and Aug was respectively 11.2, 13.8 and 6.1 cm. The average temperature for each of the same 3 months was 15.6, 19.5 and 17.2°C.