Potato, Wireworm Control, Pasco, Washington, 1977

Abstract

Abstract The test was conducted in a grower’s center-pivot, sprinkler-irrigated field. The soil type was Ritzville (Calciorthidic Haploxerolls) silt loam; it contained less than 0.5% organic matter. On Mar 31 and Apr 7, soil samples were taken with a 5 1/2-in. diam posthole digger to a depth of at least 18 in. in the vicinity of the test site (ca. 10 acres) to estimate the wireworm population; 5 wireworms were found in 90 samples. Soil temperature at depths of 9, 12, and 18 in. was ca. 10°C. Two adjacent blocks were used; one was treated by preplant broadcast and one by sidedress applications at planting. Both blocks were divided into 2 subblocks, each of which contained several insecticide treatments and an untreated check. Each plot measured 50-ft long and 60rows wide (34-in. apart), and each treatment was replicated 4 times in a randomized complete block design within each subblock. On Apr 27 and 28, broadcast treatments were applied; granules were applied with a hand-operated grass seeder, and EC formulations were diluted in water to a volume of 1 qt and applied with a hand-held, 2-row sprayer with a boom consisting of 4 Teejet (No. 8001) nozzles 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 in. within 2 hr after appli-cation. On Apr 30, potato seed pieces were planted by the grower and on May 3 and 4, sidedress treatments were applied 2 rows at a time, 3-4 in. to each side of and level with the seed piece. Granules were applied with tractor-mounted Gandy applicators in 1-In. bands, and EC formulations were diluted to a volume of 1 pt and applied at a pressure of 30 psi with Teejet 35 (No. 4916) nozzles with a tractor-mounted applicator. On Oct 5 and 6, tubers were harvested from rows 2 and 5 of each plot (15 ft/row). All were washed and examined, then the percentages, by weight, of injured and culled tubers were determined. “Injured” was defined as any penetration of c tuber by a wireworm, and “culled” 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 to arcsine percentage and analyzed by analysis of variance (split-plot design) and Duncan’s multiple range test. The methods of application were considered main-plot treatments, and the compounds or formulations were subplot treatments. Subplot treatments that were not used in both main plot treatments were not included in the analysis.