Evaluation of systemic insecticides for the control of Colorado potato beetle, potato leafhopper, and aphids in potato, 2014 *

The objective of this experiment was to assess the efficacy of at-plant systemic insecticides to control insect pests in potato. This experiment was conducted at Hancock Agricultural Experiment Station located 1.1 mile (1.8 km) southwest of Hancock, WI, on a loamy sand soil in 2014. Potato, Solanum tuberosum cv. “Russet Burbank,” seed pieces were treated on 28 April and planted on 2 May. Seed pieces were spaced 12 inches apart within rows, and rows were spaced 3 ft apart. Four-row plots were 12 ft in width by 20 ft in length, for a total of 0.006 acres. Two untreated guard rows separated plots. Plots were arranged in an 8 tier design with 12-ft alleys between tiers. All plots were maintained according to standard commercial production practices by Hancock Agricultural Experiment Station staff. Four replicates of 14 experimental treatments and 1 untreated check were arranged in a randomized complete block (RCB) design. Seed treatments were applied in 125 ml of water per 50 lb of seed on 28 April using a single nozzle boom applying 10.8 gpa equipped with a Tee Jet XR8002VS flat fan spray tip powered by a CO ₂ backpack sprayer at 30psi. In-furrow insecticides were applied at planting with a CO ₂ pressurized backpack sprayer operating at 30 psi with a 2 nozzle boom with Tee Jet 8001 flat fan nozzles delivering 11 gpa. Furrows were cut using a commercial potato planter without closing discs attached. Immediately after the in-furrow treatments were applied and all seed piece treatments were placed in open furrows, all seed were covered by hilling.

Stand counts were conducted on 3 June days after planting (32 days after planting) by counting the number of emerged plants per 20-ft section of row. Efficacy of CPB control was assessed by counting the number of stadia per plant on 10 randomly selected plants in each plot. Defoliation ratings (% DF) were determined by visual observation of the entire plot. CPBs were recorded in the following life stages: adults, egg masses, small larvae, and large larvae. Potato leafhoppers were recorded as nymphs or adults. Adult PLHs were sampled using sweep net techniques (15 sweeps per plot). PLH nymphs and aphids were assessed by visual inspection of 25 leaves per plot. Insect counts occurred on several dates throughout the summer, and insect count averages reflect time periods during the summer when specific life stages peaked in the plots ( Table 1 ). Data sets were analyzed using analysis of variance, and means were compared using a Fisher’s protected LSD means separation test ( P  = 0.05). No signs of phytotoxicity were observed among experimental treatments.

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