Insecticide Efficacy Against Sugarcane Aphids in Sorghum, 2016

The sugarcane aphid (SCA) was first detected in small numbers in Kansas in August, 2014, and only in spotty locations in south central Kansas. However, by 2016, the aphid had migrated in large enough numbers to cause considerable economic problems for many Kansas growers. Fields with significant SCA pressure were selected for these trials located in Saline (Table 1) and Dickinson (Table 2) Counties, Kansas, and treatments were applied when plants were in flowering to soft dough stages. Plots were four rows (10 ft) wide by 30 ft long with four replications of each treatment arranged in an RCB design. Insecticides, application rates and dates, and evaluation dates are provided in Tables 1 and 2. Treatments were applied using a hand sprayer delivering 20 gpa at 30 psi. Evaluations were made by counting SCA on 10 randomly selected flag leaves/plot (Table 1) and 10 randomly selected flag leaves plus 10 randomly selected bottom-most green leaves/plot (Table 2). Pretreatment counts averaged 269 −312 SCA/leaf. Data were analyzed using ANOVA and mean comparisons made by LSD (P ≤ 0.05).

At both locations, beneficial insect populations developed rapidly in the check plots and provided some control of SCA populations, especially late in the season. No phytotoxicity was observed in either trial.

In Table 1, all treatments provided significant control at 4 DAT compared to the check plots, with Sivanto providing the best control, although it was not significantly different from Transform, or either rate of Carbine or Centric. Sivanto had the lowest number of SCA at 20 DAT, although it was not significantly different from Exirel at either rate. In contrast, Carbine, at the higher rate, and Centric, at the lower rate, were not significantly different from the check. Throughout the trial, winged SCA continued to migrate into the plots, although they did not appear to be able to establish new colonies in plots treated with Centric for the first 7 DAT or Sivanto for the duration of the trial.

In Table 2, at 3 DAT all treatments containing Sivanto had the fewest SCA and this trend carried through to the 28 DAT evaluation. Lorsban, Fastac, and Warrior II provided significant control of SCA initially, but SCA numbers were increasing by 14 DAT. These compounds were also effective at eliminating beneficial insects which may have allowed SCA populations to rebound whereas beneficial populations built up and provided control of SCA in the check plots.

This research was supported in part by grants from industry.