Efficacy of Unregistered Soil-Applied Materials for Flea Beetle and Aphid Control in Tobacco, 2017

The efficacy of unregistered soil-applied insecticides against tobacco flea beetles and green peach aphids was assessed at the Upper Coastal Plain Research Station (UCPRS) in Rocky Mount, NC. At this location, six treatments, including an untreated check, were arranged in a randomized complete block (RCB) design with four replicates per treatment (Table 1). Experimental materials were applied to greenhouse transplant trays 1 day before transplant using a CO₂-pressurized sprayer fitted with a single-nozzle boom affixed with a flat fan nozzle in a spray volume of 1 liter per four trays. Immediately after application, treatments were washed into the soil media using twice the application volume of plain water. Plants with different treatments were kept in separate float beds to prevent cross-contamination. Plots were planted on 21 Apr, and each 0.018 acre plot consisted of four, ca. 25 plant, rows. The number of flea beetle holes on 10 plants in each of the middle two rows was counted 4 wk after transplant (WAT) and 5 WAT. These plants were given a phytotoxicity rating on the following scale: 0 = no observed phytotoxicity, 1 = yellowing of plant, but no stunting, 2 = stunting of plant occurred, and 3 = stunting and leaf necrosis. To measure any difference in plant growth due to applied materials, the width of the largest leaf on each of the same plants was measured during this time period. Starting 7 WAT, stand and the number of plants infested with reproducing wingless aphids was counted in the middle two rows of each plot. Data were analyzed in SAS v. 9.4 via proc mixed with treatment, date, and treatment × date interactions as fixed effects and replicate nested in treatment as a random effect. If significant treatment × date interactions occurred, means were compared within each date. Means were separated by Fisher’s protected LSD (α = 0.05).

No significant interaction between insecticide treatment and sample date was observed for phytotoxicity (F = 1.05, df 5, 18, P = 0.42); therefore, data presented are means across sample dates. Minimal phytotoxicity was observed following insecticide application, and no significant differences in phytotoxicity ratings were observed among treatments. On 6 May, no significant differences in leaf width were detected among treatments, whereas on 25 May, Admire Pro resulted in significantly greater leaf width than that observed in the untreated check (Table 1). For both flea beetle damage and percent aphid infested plants, no significant interaction between insecticide treatment and sampling date was observed (F = 1.71, df = 5, 18, P = 0.18 and F = 1.78, df = 15, 45, P = 0.06, respectively), so overall means are presented below. Admire-treated plants had significantly fewer flea beetle holes per leaf compared with plants in plots that received any of the other treatments (Table 2). Aphid numbers were low and variable, and no significant differences were observed among treatments (Table 2). This research was supported by industry gifts of product and research funding.