Control of Leaf-Feeding Insects of Flue-Cured Tobacco with Soil Applied Insecticides, 1983

Tests were established on commercially grown tobacco in Wayne (Test 1) and Hertford (Test 2) Co., N.C. Soil types were Goldsboro (Test 1) and Norfolk (Test 2) sandy loam. Plots were 16-ft wide (four rows) and 75 ft long (0.0267 acre) and were separated laterally by vacant rows and on each end by 12- or 20-ft turn alleys. Treatments were arranged in a randomized complete block design with three replications. Broadcast sprays were applied 29 Apr., Test 1; 5 May, Test 2) using a tractor-mounted boom sprayer delivering 21.8 and 23.4 gal/acre in Tests 1 and 2, respectively, through 8004 flat fan nozzles at 25 lb/in2. Granular broadcast applications were made using two electrically driven tractor-mounted Gandy applicators. All broadcast applications were incorporated by discing twice in opposite directions. Temik narrow band treatments were applied in a 2 to 3-in. band using an applicator shank (3 May, Test 1; 13 May, Test 2). Granules were placed ca. 3 in. below the surface of a partially formed bed and covered with an additional 2 to 3 in. of soil. Transplant water applications were made using the farmers’ tractor-drawn transplanters (Test 1: 9 May, 320 gal/acre; Test 2: 13 May, 208 gal/acre). Sidedress treatments were applied (14 Jun., Test 1; 16 Jun., Test 2) in a 2 to 3-in. band to one side of each row ca. 2 in. below the surface. Insect counts and damage ratings were made on the middle two rows of each plot. Budworms were counted on 20 or 40 plants and the same plants rated for budworm damage: 0, no damage; 1, light damage typical of feeding by 1st to 3rd stage larvae; 2, heavy damage typical of feeding by large larvae; 3, plant topped by feeding. Flea beetles were counted on 10 plants and the number of feeding holes counted on the uppermost leaf over 6 in. long of the same plant. Green peach aphids were counted on the uppermost leaf over 6 in. long of 10 plants. Twenty plants were rated for overall aphid infestation: 0, no aphids seen; 1, 1 to 10 apterous aphids on most infested leaf; 2, 11 to 50 apterous aphids on most infested leaf; 3, 51 to 200 apterous aphids on most infested leaf; 4, 200+ apterous aphids on most infested leaf; 5, plant heavily infested, honeydew and sooty mold obvious. Hornworms (mixed species) were counted on 20 plants. After harvest and curing, tobacco from each plot per harvest was weighed and given a government grade. Grades were converted to a quality index (1 to 99) and a weighted average computed. All variables were subjected to analysis of variance and means separated using the Waller-Duncan K ratio t test (K ratio = 100). For analysis, aphid, budworm, flea beetle and hornworm numbers were transformed to the square root of N + 0.5.