Evaluation of Selected Broadcast and Band-Applied Foliar Insecticides for Control of Thrips in Cotton, 2014 * Open Access

Selected foliar insecticides, broadcast or band-applied, were evaluated for control of thrips in cotton. ‘DP 1028 B2RF’ cotton was planted 6 May at the Virginia Tech Tidewater Agric. Res. & Ext. Ctr., Suffolk, VA, using 36-inch row spacing. The foliar applications of Radiant, Orthene, Levo, and Exirel were made at the first true leaf stage on 22 May with a CO ₂ -pressurized backpack sprayer, with Levo and Exirel applied again on 30 May. Radiant was tank-mixed with the crop oil concentrate, Agri-Dex. Aeris-treated seed was used for all plots except for those with Levo or Exirel applications. The broadcast boom was calibrated to deliver 14.3 gpa and 18 psi through 8002VS nozzles spaced 18 inches apart; the band boom was set to 16.8 gpa at 23 psi through 8004E nozzles spaced 36 inches apart. A RCB design was used with 4 replicates; plots were four rows by 40 ft. Thrips injury to plants was determined on four dates by visually rating injury using a 0–5 scale, where 0 = no thrips induced plant injury; 1 = 10% injured leaves, no bud injury; 2 = 25% injured leaves, no bud injury; 3 = 75% injured leaves, and 0–25% buds injured; 4 = 90% injured leaves, and >25% buds injured; and 5 = dead plants. Thrips counts were taken on four dates by collecting five plants per plot in Mason jars containing ∼500 ml soapy water. Immature and adult thrips were counted under a stereoscope following suction filtration. Yield was determined by harvesting two rows of each plot (end-trimmed to 64 row ft) using a commercial two-row cotton picker. Sub-samples were ginned to determine lint versus seed and trash weight (43.8% lint, 56.2% seed and trash). Data were analyzed using ANOVA and LSD statistical procedures.

There were differences in thrips injury ratings between treatments on all sample dates ( Table 1 ). Plots using Aeris-treated seed had lower thrips injury ratings on every sample date. In plots with Aeris-treated seed, the use of broadcast compared with band-applied insecticide did not consistently alter injury ratings across sample dates and there was no significant difference in yield. Thrips counts in treatments using Aeris-treated seed with no insecticide were often higher than counts in treatments using Aeris plus insecticides, although the Aeris-only plots had the numerically highest yield of all treatments.

Author notes