Effect of Soil-Applied Insecticides and Insecticide Placement on Tobacco Flea Beetle and Tobacco Aphid in Flue-Cured Tobacco, 1991

Abstract

Abstract Combinations of soil-applied and over-the-top insecticides and insecticide placement and timing were tested in two trials conducted on commercial farms in Lenoir Co. (LC) and Wayne Co. (WC), NC. Plots were 4 rows wide and 0.02 acre in area, separated laterally by a vacant row and on each end by a 16-20 ft turn alley. Treatments were arranged in a randomized complete-block design with 4 replications. Tobacco (K-149, LC; K-326, WC) was transplanted on 19 Apr (LC) and 25 Apr (WC) into a Norfolk sandy loam. Broadcast treatments were applied on 10 Apr (LC) through 8004 flat fan nozzles delivering 21 gal/acre at 20 psi and incorporated immediately by discing twice. Granular band treatments were applied in an 8 inch band using an electrically driven granular applicator and incorporated by bedding over the band. Shanked treatments were applied immediately prior to transplanting into a pre-formed bed which had been leveled to final transplanting height. A narrow (1.5 inch) fertilizer shank placed granules 5 (WC) or 6 (LC) inches below the bed surface in the row center or 5-6 inches below the bed surface and 5 inches to one or both sides of the row center. In the latter treatment, 1/2 rate was delivered to each side. Soils were moist but not wet and above 21°C at the time of all insecticide applications. Transplant water (TW) treatments were made in Lenoir Co. using the farmer's mechanical transplanter delivering 125 and in Wayne Co. by hand applying 130 gal/acre. Over-thetop (OT) sprays were applied through 3 hollow cone nozzles/row at 60 psi delivering 24 gal/acre. These sprays were applied at threshold for the tobacco aphid (10% plants infested) or on 1 or 2 schedules (5, 7, and 10 wk after transplanting or 5, 7, and 9 weeks after transplanting). Plots were checked weekly through the growing season. Flea beetles and flea beetle feeding holes were counted on 10 and 5 plants respectively in each of the 2 center rows of the plot. Aphid infestation was rated on all plants in each plot (0 = no aphids, 1 = 1-9 aphids on most infested leaf, 2 = 10-49 aphids on most infested leaf, 3 = 50-200 aphids, 4 = 200-500 aphids, 5 = 500+ aphids on most infested leaf). Plants rated 3 or above were considered infested in determining thresholds. Data were subjected to analysis of variance and means separated using the Waller-Duncan K-ratio t test.