Efficacy of Soil Applied and Foliar Materials for Lepidoptera Control in Tobacco, 2014 * Open Access

The efficacy of one soil applied and several foliar insecticides against lepidopteran pests of tobacco were assessed at two locations, the Lower Coastal Plain Research Station (LCPRS) in Kinston, NC and the Upper Coastal Plain Research Station (UCPRS) in Rocky Mount, NC. At each location, eight treatments, including an unsprayed check, were arranged an RCB design with four replicates per treatment ( Table 1 ). Each 0.018 acre plot consisted of four, ca. 25 plant, rows. All plants were treated in the greenhouse with Admire Pro 4.6F (Bayer Crop Sciences) at a rate of 0.6 fl oz/1,000 plants 1–7 d prior to transplanting to control aphids and flea beetles. Plants were transplanted on 8 May at LCPRS and on 5 May at UCPRS, and in-furrow transplant water (TPW) treatments were applied in ca. 160 GPA of water using four 5-gal mini-tanks affixed to the planter. Tobacco budworms (TBW) were counted on all plants in the middle two rows weekly, beginning 3 wk after transplant and continuing to the week of topping. Plants were topped on 15 Jul at LCPRS and 29 Jul at UCPRS after which hornworms (HW) on all plants in the middle two rows were counted weekly until the end of the experiment. Foliar materials targeting TBW were applied when >15% of plants in the field were infested with at least one caterpillar, and HW targeting materials sprayed when HW infestation exceeded one nonparasitized caterpillar per 10 plants. Only one application per target pest was applied, even if pest populations rebounded.

TBW-targeting sprays were applied to all plots using a CO ₂ -pressurized backpack sprayer fitted with a single T2 solid-cone at 52 psi pressure and 15 GPA spray volume. These applications were performed on 18 Jun at LCPRS and 1 Jul at UCPRS. TBW counts were taken 2, 6, 14, and 19 d after treatment (DAT) at LCPRS and 2, 8, 13, and 21 DAT at UCPRS. HW-targeting treatments were applied with the same sprayer fitted with a single T3 solid-cone at 65 psi pressure and 30 GPA spray volume. These treatments were applied at UCPRS on 16 Aug, and HW counts were performed 3, 6, and 11 DAT. HW populations remained too low to treat at LCPRS throughout the season. All data were analyzed via analysis of variance (Proc mixed; SAS v. 9.3.1) with treatment as the independent variable and replicate nested in treatment as a random effect. Means were separated by Fisher’s Protected LSD (α = 0.05).

At both locations, TBW populations did not exceed the economic threshold of 10% of plants infested with at least one budworm until the week of the pretreatment count. In both instances, the TPW Coragen treatments did not lower TBW infestation below this threshold for longer than the untreated plots ( Tables 1 and 2 ). After foliar materials were applied, significant differences between sprayed and unsprayed plots occurred within 2 DAT at both locations ( Tables 1 and 2 ). At LCPRS, a prolonged budworm flight coupled with rapid plant growth at the time of treatment led to high levels of re-infestation with all plants above the economic threshold within 2 wk of treatment ( Table 1 ). At UCPRS, TBW pressure was reduced below the economic threshold in foliar-treated plots within 8 DAT, but by 13 DAT caterpillars were below threshold for all plots, likely due to the pupation of mature caterpillars. Residual from the TBW-targeting foliar Coragen and Besiege applications may have caused the significantly different pretreatment HW counts. After applying HW-targeting foliar treatments, nonparasitized hornworm counts were both significantly different from unsprayed plots and below economic threshold ( Table 3 ). By 11 DAT, HW counts were too low to analyze for all treatments, again likely to pupation of mature individuals.

Author notes