Potato Wireworm Control, Pasco, Washington, 1975

The soil type was Ritzville Series, silt loam, with less than 0.5% organic matter. On March 3 and 11, soil samples were taken with a posthole digger to estimate the wireworm population. Thirteen wireworms were found in 132 samples, a calculated density of 0.9 wireworms/ft2, based on a 95% confidence limit. Preplant broadcast and at-plant band treatments were separate experiments. Each treatment was replicated 4 times in a randomized complete block design. Individual plots were 6 rows wide (34 in apart) and 50 ft long. On April 29, the preplant broadcast treatments were applied and incorporated into the soil. Granules were broadcast with a hand-operated grass seeder, and EC formulations were applied with a hand-held 2-row sprayer consisting of 4 Teejet nozzles. The EC formulations were diluted in water to a volume of 1 qt and applied at a rate of ca. 12.8 gal/acre at a pressure of 30 psi. The plots were rototilled to a depth of 6 inches within 2 hr after application. Potatoes were planted on May 22 and on May 23, the at-plant band treatments were applied 4 inches to each side and level with the seed pieces. Granules were applied with tractor-mounted Gandy applicators in 1-inch bands, 2 rows at a time. The EC formulations were diluted in water to a volume of 1 qt and applied at a pressure of 30 psi to 2 rows at a time by using a tractor-mounted applicator. All plots were sprinkler irrigated. Tuber samples were harvested on October 6 to 8 from the 2 center rows of each plot (15 ft/row). All samples were washed and examined, and the percentages, by weight, of injured and culled tubers due to wireworms were determined. “Injured” was defined as any injury severe enough to meet the description of “damage” in Sec. 51.1554 of the U. S. Standard for Potatoes. The percentages were transformed toX + 0.5 and analyzed by analysis of variance (split-plot design) and Duncan's new multiple range test.