Colorado Potato Beetle Control, 1987
Authors: Bishop B. , Grafius E. , Hayden J. , Stehr J. , Davis A. , Ioannidis P. 
Published: March 2022

Potatoes were planted 24 Apr at the MSU Montcalm Potato Research Farm. Plots were 3 rows wide (34-inch row spacing) by 40 ft long. Two unsampled rows were left between adjacent plots. Treatments were arranged in a randomized complete block design with 4 blocks per treatment. Treatments were applied as foliar sprays with a tractor-mounted boom sprayer at 30 gal/acre, 40 psi, with a cluster of 3 nozzles over each row. The middle nozzle directed spray down over the top of the plant, and the other nozzles directed the spray at the sides of the plant. Treatments for control of first-generation Colorado potato beetle were applied on 15 and 22 Jun (with the exception of the DPX-EY059 treatment, which was applied only on the first date). Insects were counted on 10 Jun (pretreatment count), 18 Jun (after first treatment), and 25 Jun (after second treatment). Randomly selected plants from the middle row of each plot were sampled (3 plants/plot on the first date; 2 plants/plot for each of the postspray dates). Damage ratings per plot and plant (2 plants per plot) were made on 25 Jun. Damage ratings were based on a scale of 1 to 5, where 1 indicated no damage (per plant or per plot), 2 indicated 0-5% defoliation (per plant or per plot), 3 indicated 5-25% defoliation, 4 indicated 25-50% defoliation, and 5 indicated 50-100% defoliation. Beetle numbers were low in first-generation plots on 25 Jun, but rose sharply again in July (due to emergence of second-generation beetles). To maintain differences in yield and foliage damage levels due to first generation beetles, these plots were sprayed with Furadan 4F (1 lb [AI]/acre) on 16 Jul and again on 18 Aug. Damage ratings were again taken of first-generation plots on a per-plot basis on 28 Jul (about 1 mo after last treatment application). New growth of badly damaged plants had made the previously used damage scale unusable, so damage ratings were made on the basis of percentage of soil visible in plots (1, no soil visible—least damage; 2, 1-5% of soil visible; 3, 5-25% of soil visible; 4, 25-50% soil visible; and 5, 50-100% of soil visible— most damage). Treatments for control of second-generation Colorado potato beetle were applied on 17 Jul and 17 and 23 Jul (again, with the exception of the DPX-EY059 treatment, which was applied only on the first date). Insects were counted on 2 randomly selected plants from the middle row of each plot on 14 Jul (pretreatment count), 21 Jul (after first treatment), and 28 Jul (after second treatment). Furadan 4F was sprayed on second-generation plots on 23 Jun to suppress first-generation beetles. Nonetheless, damage occurred to these plots before treatments were applied. To check for significant differences in damage between plots before the first treatment, a plot damage rating was made on 14 Jun. Damage ratings were also made on a per-plot and per-plant basis, according to the scale described previously, on 28 Jul (after second treatment). Furadan 4F was again sprayed on all second-generation plots on 18 Aug. Potatoes were harvested from middle row of each plot and weighed (first- and second-generation plots) on 7 Oct. Data (insect numbers, damage ratings, and harvest weight) were analyzed by a two-way analysis of variance at P = 0.05. Tukey's test was used to test for nonadditivity. Multiple comparisons (SNK) were made where significant results were obtained.