Potato Wireworm Control, Pasco, Washington, 1976

The soil type was Ritzville Series, silt loam, with less than 0.5% organic matter. On March 16 and 17 soil samples were taken with a posthole digger to a depth of at least 18 inches to estimate the wire-worm population. Five wireworms were found in 40 samples in an area of ca. 10 acres, a calculated density of 1.1 wireworms/sq ft (the upper 95% confidence limits). Individual plots were 6 rows wide (34 inches apart) and 50 ft long. Treatments applied as separate experiments were preplant broadcast, at-plant furrow, and at-plant band. Each treatment was replicated 4 times in a randomized complete block design. For the preplant broadcast treatments applied May 11 and 12, granules were broadcasted with a hand-operated grass seeder, or EC formulations were applied with a hand-held, 2-row sprayer with a boom consisting of 4 Teejet (No. 8001) nozzles. 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 4-6 inches within 2 hr after application. The two other treatments were applied after the potatoes were planted May 13. On May 13 and 14 the furrow treatments were applied in the seed-piece furrows left uncovered (by raising the discs of the planter) when the grower planted the seed pieces.