Abstract
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.