Evaluation of Insecticides for Control of Picture-Winged Flies in Sweet Corn, 2017

A field experiment was conducted at the UF/IFAS Everglades Research and Education Center in Belle Glade, FL to evaluate the efficacy of foliar insecticides for management of a three-species complex of picture-winged flies infesting sweet corn ears. Five insecticide treatments and a nontreated check were evaluated in an RCBD with four blocks and one replicate per block. Sweet corn (Syngenta BSS1075) was planted on 13 Feb on 30-inch centers at a density of 32,000 seeds/acre. Plots were eight rows wide and 34 ft long. Each insecticide treatment was applied 10 times between first silk and maturity (8 Apr, 10 Apr, 12 Apr, 14 Apr, 17 Apr, 19 Apr, 21 Apr, 24 Apr, 26 Apr, and 28 Apr). Treatments were applied using a CO₂-pressurized backpack sprayer calibrated to deliver 15 gpa at 30 psi ≈ 1 ft above the canopy. A boom equipped with eight Teejet TP11001VS spaced 15 inches apart was used. Adults of the three picture-winged fly species were observed in nontreated check plots throughout the evaluation, with Euxesta eluta being the most prevalent. Besiege at 10 fl oz/acre (16 Mar, 4 Apr), Rimon at 9 fl oz/acre (11 Apr), and Coragen at 4 fl oz/acre (18 Apr) were applied with commercial spraying equipment for fall armyworm, Spodoptera frugiperda (J.E. Smith), management.

Fly injury and infestation data were collected 3 and 4 d after the last application. For each plot, 20 ears were randomly selected on each of the two center rows (40 ears/plot). For each ear, silk fly injury was rated following a 0 to 5 rating scale (0: no injury, 1: silks injured, 2: tip injured, 3: top 25% injured, 4: top 50% injured, 5: >top 50% injured). The number of fly maggots was also counted for each ear. Data were analyzed using linear mixed models (PROC GLIMMIX, SAS Institute). Means were separated using Tukey’s HSD (α = 0.05).

Differences among treatments for % ears injured, fly injury rating, % ears infested, and number of fly maggots/ear were detected (P < 0.05; Table 1). The Mustang (commercial pyrethroid standard) and Radiant treatments were associated with the greatest reductions in fly injury with 40 and 57% decreases in % ears injured and 49 and 62% decreases in injury ratings, respectively, relative to the nontreated check. In addition, the Mustang and Radiant treatments were associated with the lowest infestation levels, decreasing the number of maggots/ear by 67 and 73%, respectively, relative to the nontreated check. The Lorsban Advanced treatment was not different from the Mustang and Radiant treatments. Although the Agri-Mek treatment seemed to provide intermediate levels of fly control, differences between Agri-Mek-treated plots and nontreated plots were not detected at the 5% level except for % ears infested (47.5 vs. 78.1%, respectively). The Sivanto Prime treatment was not associated with decreases in silk fly injury and infestation levels.

This research was partially supported by industry gifts including seed and products.