Potato, Wireworm Control, Hermiston, Oregon, 1978
Authors: Turner J. E. , Toba H. H. 
Published: March 2022

The test was conducted at the Oregon State University Columbia Basin Experiment Station in a solid-set, sprinkler-irrigated field. The soil type was Ephrata sandy loam (Xerollic Camborthids) with an organic content of less than 1%. On Apr 5, five soil samples were taken at each of ten sites in the test area (ca 3 acres) with a 5 1/2 inch posthole digger to a depth of at least 18 inches. Three wireworms were found in 50 samples. The soil temperature was 12°C at 6 inches and 10°C at 12 and 18 inches. The test was a split block design. There were four different application methods; pre-plant broadcast, at-plant sidedress, in seed furrow, and postemergence sidedress. Each block was divided into two subblocks, each subblock having its own untreated check. Each replicate measured 40-ft long and 4 rows (11.3 ft) wide (34-inch row spacing). Each treatment of insecticide was replicated 4 times in a randomized complete block design within each subblock. On Apr 25, the broadcast materials were applied. Granular materials were broadcast with a hand-operated Cyclone grass seeder, and the EC formulations were applied with a CO2 hand-held, 2-row sprayer with a boom consisting of four Teejet (No. AL80015) nozzles. EC formulations were diluted in water to a volume of 1 pt 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 to 6 inches within 1 hr after application. Then on Apr 26-27 and May 1-2, potato seed pieces were planted with a 2-row planter. The at-plant sidedress and seed piece furrow applications were made during the planting operation with applicators mounted on the planter. For sidedress application, the granules were shanked 3-4 inches to each side and level with the seed pieces In 1-inch bands with Gandy applicators, and the EC formulations were diluted in water to a volume of 1 pt when applied at a pressure of 40 psi with Teejet No. 4916-35 nozzjes attached to the rear of the shanks. For furrow applications, the granules were placed in 1-inch bands through the planter shoe, level with and directly behind the seed, and EC formulations were applied with Teejet No. 8004F nozzles in the rear of the planter shoe. In addition, 6-inch band applications were made by applying the chemicals ahead of the planter shoe: for granules, a deflector was attached to the end of the delivery hose so as to produce a 6-inch band; for EC materials, the height of the nozzle, Teejet No. 8004F, was adjusted to deliver a 6-inch band. On Jun 2, postemergence sidedressed materials were applied with a two row tractor mounted Gandy and EC applicators, in a manner similar to the at-plant sidedressed materials. On Oct 3-5, tuber samples were harvested from the two center rows of each replicate (ca 15 ft/row). All tubers were washed and examined for wireworm damage and the percentages, by weight, of tubers injured and culled because of wireworms were determined. “Injured#x201D; was defined as any penetration of a tuber by a wireworm. “Culled#x201D; was defined as any injury severe enough to meet the description of “damage#x201D; in Sec. 51.1560 and 51.1564 of the U. S. Standards for Grades of Potatoes. Because of significant differences in percentages of injured and culled tubers in the untreated check plots between subblocks, all the percentages were converted to percent control so the treatments could be compared with each other. These percentages were then transformed to arcsine percentage and analyzed by analysis of variance (split-plot design) and Duncan's multiple range test. Materials that were not applied by all 4 application methods and those that were applied in 6-inch bands were not included in the analysis.