Wireworm Control on Sweet Potatoes, 1971

Shell DD at 10 gallons per acre was applied in row for nematodes on May 10, 1971. Sweet potatoes 'Jewel' were planted on June 1 near Bentonville, NC. Preplant treatments were applied on May 26. Foliar treatments were applied on June 7, 21, and 28. The lay-by treatment was applied on July 16 when roots were enlarging. Nonreplicated plots consisted of 5 rows 450 ft long (1/7 acre). Soil was classified as a Norfolk sandy loam with adequate soil moisture. Granular insecticides were applied broadcast preplant and over the row with a hand-cranked cyclone seeder. Foliar sprays were applied with a compressed hand sprayer at the rate of 20 gallons per acre at 40 psi. Wireworm damage was evaluated by scoring 100 roots selected at random from center rows on October 29. Damage classes were: 0 = no damage; 1 = up to 5 holes; 2 = 6 to 10 holes; and 3 = 1 1 or more holes/sweet potato. When this damage was averaged, a “damage index” was obtained. “Percent damage control” was arrived at by the following formula: for treated sweet potatoes let A = the damage index and B = the % treated sweet potatoes damaged; for untreated (check) sweet potatoes let X = the damage index and Y = the % sweet potatoes damaged; then 100 - (AB/XY × 100) = percent damage control, a factor which reflects the effectiveness of the insecticide by comparing wireworm damage to potatoes from treated plots with potatoes from untreated plots.