Control of Aphids on Potato, 2015

The ability of aphids to spread viruses makes it very important to continue testing new chemistries and the efficacy of existing compounds. The experiment was conducted at Presque Isle, ME in 2014 and replicated six times. The experimental design was randomized complete block, with plots being four rows wide (12 ft) and 30 ft long. A 10 ft space was left fallow between blocks and a 6 ft space was left fallow between the plots within the blocks.

The crop was planted on 27 May using hand cut ‘Shepody’ potato seed. A John Deere 216 two-row potato planter was used to make open furrows applying 1,100 pounds of 14-14-14 fertilizer per acre. The seed was hand placed at 12-inch spacing. The rows were mechanically covered, placing the seed piece approximately 3 inches below the surface. Foliar insecticide applications were made with a modified Century boom sprayer, eight nozzles per rep, 40 gpa at 35 psi, boom height 20–24 inches, and tractor speed 3 mph. Blackhawk (3.2 oz/acre) was applied to all treatments on 14 Jul to prevent excessive defoliation by Colorado potato beetles. The crop was treated with Bravo ZN at 5–7 day intervals based on recommendations from the University of Maine Cooperative Extension throughout the season for controlling late blight.

Aphid numbers (by species) were counted weekly on one top, one middle, and one bottom leaves of 20 plants selected at random in the middle two rows of each plot. When dates of count and application were the same, counts were made prior to applications of the insecticide. Analyses of variance were conducted following transformation of the data using log ₁₀ (X + 1), and means were compared using Fisher’s LSD Test. Means followed by the same letter do not significantly differ from each other ( P= 0.05).

The soil was classified as Caribou Gravely Silt Loam, pH 6.0. The total monthly rainfall for June, July, and August was respectively 4.47, 2.57, and 3.52 inches, and the mean temperature was 69.3, 76.5, and 78.4 °F.

No phytotoxicity was observed with any of the treatments.

The purpose of this experiment ( Table 1 ) was to test the compatibility of foliar aphicides with crop oil to control the aphid population. Movento applied alone or with JMS Stylet oil provided the best aphid control, followed by Fulfill and Sivanto. Unexpectedly, applications of Admire Pro resulted in poor aphid control. No interference between insecticides and JMS Stylet oil was observed. To the contrary, Fulfill applied with JMS Stylet oil showed better aphid control than Fulfill applied alone. The aphid population crashed due to natural causes between the 14 Aug and 18 Aug scouting dates.

This research was supported by industry gifts of pesticides and money.

Author notes