Evaluation of Foliar Insecticides for the Control of Colorado Potato Beetle in Potatoes, 2017

The objective of this experiment was to assess the efficacy of Exirel and Besiege applied once or twice for the control of CPB on potatoes. The experiment was conducted at the Virginia Tech Eastern Shore Agricultural Research and Extension Center in Painter, VA and consisted of four treatments arranged in an RCB design with four replicates. ‘Superior’ potatoes were planted on 9 Mar 2017. Plots were 2-row wide and 20-ft (6.1 m) long with unplanted guard rows on each side. Rows were planted on a 3-ft row center (0.9 m) with 11 inches (0.3 m) between plants, in a 6-tier field design with 8-ft (2.4 m) alleys between tiers and a 16-ft (4.9 m) center alley. All foliar treatments were applied with a 4-nozzle boom equipped with 110003VS spray tips spaced 20″ apart spraying two rows at a time and powered by a CO₂-backpack sprayer at 40 psi delivering 38 gpa. All plots were maintained according to standard commercial practices.

On 24, 31 May and 6 Jun, the number of all life stages of CPB was recorded per 10 stems per plot. On 6 Jun, percentage defoliation was estimated visually for each 2-row plot. On 12 Jun, the number of PLH nymphs was recorded per 15 compound leaves. On 6 Jul, all potato tubers were mechanically harvested and weighed and graded by size. Data were analyzed using ANOVA and means were separated using Tukey’s HSD at the 0.05 level of significance.

CPB pest pressure was moderately high with an average of >80 larvae (large larvae and small larvae combined) per 10 stems on 31 May in the untreated check plots. On 24 May (7 DAT), all treatments had significantly fewer CPB small larvae than the untreated check except Besiege (Table 1). All treatments also had significantly fewer large larvae than the untreated check. On 31 May (7 DAT for Exirel and Besiege applied twice and 14 DAT for Exirel and Besiege applied once), all treatments had significantly fewer small and large larvae than the untreated check (Table 1). On 6 Jun (13 DAT for Exirel and Besiege applied twice and 20 DAT for Exirel and Besiege applied once), all treatments had significantly fewer small larvae and CPB adults than the untreated check (Table 1). Percent defoliation was significant with all treatments having significantly less % defoliation than the untreated check (Table 1). All treatments had significantly fewer PLH nymphs compared with the untreated check except Exirel applied once (Table 1). There were no significant differences in tuber yield (Table 2), and no signs of phytotoxicity from any of the treatments. Insecticide products were supplied by Dupont and Syngenta.