Efficacy of Eretmocerus eremicus and Flupyradifurone on Bemisia tabaci (MED whitefly), 2017 Open Access

With the overall goal to find effective alternates to neonicotinoid insecticides for the MED whitefly management program, the specific objective of this study was to evaluate whitefly parasitoid Eretmocerus eremicus and a butenolide insecticide flupyradifurone, for whitefly control, when applied alone or in combination. The trial was conducted on mint under greenhouse conditions at Mid-Florida Research & Education Center, University of Florida (MREC-UF). Mint cuttings (5–6 inches) were taken from stock plants and placed into 6-inch pots with Professional Growing Mix (Sun Gro Horticulture). Potted plants were irrigated as needed and fertilized with Peters Professional® 20-20-20 (1 tablespoon per gal) (Scotts Co., Marysville, Ohio) every 2 wk. Four treatments (Table 1) were arranged in a RCB design with six replicates, where each replicate consisted of four plants per cage. Cages (replicate) were infested with 100 MED whitefly adults (3×) at weekly intervals, and treatment cages with E. eremicus were inoculated using 1 Eretline blister (Bioline AgroSciences, a blister pack consist about 250 wasp adults) (2×) per cage starting 2 wk after first whitefly infestations and prior to the insecticide application. Sampling of all treatments to determine an initial count of arthropods and to confirm whitefly biotype was conducted prior to the drench application (3 fl oz solution/pot) of flupyradifurone (21 fl oz/100 ga). Cages were evaluated at weekly intervals for a period of 7 wk by randomly sampling five leaves per replicate (across all four plants). The number of MED whitefly, eggs, nymphs, and adults was counted per leaf. Counts of each life stage were analyzed independently using a generalized linear mixed model with the SAS (SAS Institute, Cary, NC) procedure GLIMMIX. The model was used to determine treatment effect at each sampling period. Since the response variable was count data with no upper bound, the model statement distribution was specified as Poisson. The autoregressive correlation structure was applied to account for the correlation in data generated by resampling the same experimental unit over time. Differences among treatment means were separated using Fisher’s LSD test (α = 0.05) in the repeated measures model. The numbers of whitefly life stages in the efficacy trial were not uniform, so the Henderson–Tilton’s formula was used to calculate corrected mortality.

Eretmocerus eremicus is among the parasitoids which utilize their prey for both food and site of reproduction resulting in suppression of the pest population on the plant. In the current study, visual observation of whitefly parasitization was insignificant, and thus parasitized immatures and emerged wasps were not included in the analysis. Flupyradifurone was effective in suppressing MED whitefly immatures for the majority of study period (Table 1). In the flupyradifurone treatment, a significantly lower number of whitefly eggs, nymphs, and adults compared with the untreated control was recorded on wk 2, 4–7, wk 3–7, and wk 5–7, respectively (Table 1). Eretmocerus eremicus provided significant suppression in whitefly eggs and nymphs on wk 4–6 and wk 5–7, respectively. Numerically, the combination treatment provided the best suppression in MED whitefly population. Overall, whitefly immatures (eggs + nymphs) mortality in different treatments ranged between 72% and 98% (wk 4–7) for E. eremicus, 48% and 80% (wk 2–7) for flupyradifurone, and 57% and 100% for combination treatments. No phytotoxicity was observed for any treatment. This research was supported by the Floriculture and Nursery Research Initiative & USDA Farm Bill.