Efficacy of Eretmocerus eremicus and cyantraniliprole 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 diamide insecticide cyantraniliprole, 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, OH) every 2 wk. Four treatments–(1) control, (2) cyantraniliprole, (3) E. eremicus, and (4) E. eremicus + cyantraniliprole were arranged in a randomized complete block design with six replicates, where each replicate (cage) consisted of four plants per cage. Mint plants in each cage (replicate) were infested with 100 MED whitefly adults (3×) at weekly intervals (25 whitefly/plant), and treatment cages with E. eremicus were inoculated with ~100 parasitoids (2×) per cage starting two weeks after first whitefly infestations and prior to the insecticide application. Pretreat sampling to determine an initial count of arthropods and whitefly biotype confirmation was made prior to the drench application (4fl oz solution/ pot) of cyantraniliprole. Treatment evaluations were made at weekly intervals for a period of 7 wk by randomly sampling five leaves per replicate and recording the number of MED whitefly, eggs, nymphs and adults per leaf. Counts of whitefly life stages observed in different treatments were analyzed independently using a generalized linear mixed model with the SAS (SAS Institute, Cary, NC) procedure GLIMMIX. The model was used to determine the effect of insecticide treatments, sampling period and their interaction on the arthropod counts. Since the response variable was count data with no upper bound, in model statement distribution was specified as Poisson. The autoregressive correlation structure was applied to account for the correlation in data generated by re-sampling 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. As the number of whitefly life stages in the efficacy trial was not uniform, 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, whitefly parasitization by wasps was insignificant, and thus parasitized immatures and emerged wasps) were not included in the analysis. Cyantraniliprole was effective in suppressing MED whitefly life-stages throughout the study period (Table 1). Significantly lower numbers of whitefly eggs, nymphs and adults (except wk1) were recorded on all the sampling dates in the two insecticide-treated plots (cyantraniliprole, and cyantraniliprole + E. eremicus) compared to the untreated control (Table 1). Eretmocerus eremicus provided significant suppression in whitefly eggs and nymphs on weeks 1–7 and weeks 4–7, respectively. Numerically, combination treatment provided the best suppression in MED whitefly population. Overall whitefly mortality in different treatments ranged between 21 and 85% for E. eremicus, 71–100% for cyantraniliprole, and 88–100% for combination treatments. No phytotoxicity was observed for any treatment. This research was supported by the Floriculture and Nursery Research Initiative & USDA Farm Bill.

Author notes