Use of Eretmocerus eremicus and Amblyseius swirskii to suppress Bemisia tabaci on potted poinsettias in protected culture: Data set
Description
The purpose of this study was to determine whether using two natural enemies (a predator, Amblyseius swirskii, and parasitic wasp, Eretmocerus eremicus) in combination would be better at suppressing the main pest of poinsettias, the sweetpotato whitefly (Bemisia tabaci), compared to each natural enemy alone. To test whether the combination of the two natural enemies is superior at suppressing the whiteflies compared to each natural enemy alone, we used both a substitutive and additive design (see Sih et al. 1998. Emergent impacts of multiple predators on prey) to test for both intraspecific and interspecific interactions between our natural enemies on whitefly suppression. Experimental design: Experimental units consisted of 12 whitefly-infested potted poinsettias (subsamples) within a large cage (4 ft x 5 ft x 3 ft; w x l x h). Each trial consisted a total of 24 cages split between two adjacent greenhouses (block_greenhouse 8 and 9). Cages were assigned to one of six treatments (4 treatment replications): 1. Control. No natural enemies were released. Only whiteflies at the start of the trial. 2. Eremicus. Twenty-five E. eremicus pupae released into the cage weekly. 3. Swirskii. Two and a half milliliters of A. swirskii bulk (in carrier material, ~123 mites) spread across the 12 poinsettias at weeks 0 and 4. 4. Eremicus + Swirskii. Combination of treatments 2 and 3 above. 5. Eremicusx2. Fifty E. eremicus pupae released into the cage weekly. 6. Swirskiix2. 5 milliliters of A. swirskii bulk (in carrier material, ~246 mites) pread across the 12 poinsettias at weeks 0 and 4. At the start of the trial (week 0), total number of whitefly nymphs, pupae, exuviae, and adults were counted for every other plant within each cage prior to releasing natural enemies. Number of whitefly nymphs, pupae, exuviae, adults, A. swirskii mites, and E. eremicus adults were subsequently counted on the same plants for individual leaves (1 to 10 = lower to upper canopy) for weeks 2, 4, 6 and 8. Due to difference in subsample level (whole plant vs leaf), data is best analyzed if summed to the plant level first, prior to analysis. In our analysis (ob1_analysesv3), we averaged all plants to the cage level prior to analysis to avoid zero-inflation. Entire trial was replicated a total of three times (spring "A", fall "B", and summer). Spring and fall trials are in the same file ("wfcounts"), since initial and environmental conditions were very similar. Summer trial data is found in the "summertrial.csv" file and was ended prematurely (week 6) due to very high whitefly numbers and rapid plant health decline in all treatments. Endeavor (Pymetrozine) insecticide was applied to all treatments on week four in the summer trial, with no apparent suppression to whitefly populations. Hobo data loggers were placed inside cages in the middle of the greenhouse for each trial and recorded temperature (F) and relative humidity in 30-minute intervals.
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