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Submitted to: National Research and Action Plan for Silver Leaf Whitefly
Publication Type: Abstract Only Publication Acceptance Date: 6/1/1998 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: We compared natural enemy conservation in untreated plots and plots under 3 insecticide regimes. Treatment was replicated 4 times in 0.27 hectare plots. Whitefly populations were monitored weekly and all insecticides were applied according to recommended action thresholds. A split-plot design was created in late July when half of all plots were sprayed once to control Lygus hesperus. Weekly sweepnet samples were used to estimate the abundanc of arthropod predators, and leaf samples were used to estimate the abundance and activity of native whitefly parasitoids. Preliminary results indicate that Eretmocerus eremicus and Encarsia meritoria were present throughout the season, although the former species was dominant, comprising about 80% of all parasitoids collected. Rates of parasitism began low, generally peaked around mid-August and then declined. Parasitism averaged about 8.4% over the whole experimental area for the season. Host and parasitoid densities differed significantly among insecticide regimes on most post-treatment dates and were consistently highest for the untreated control and lowest for plots treated with pyriproxyfen. Percentage parasitism differed among treatments on 3 of 6 post-treatment dates and was generally highest for pyriproxyfen plots and lowest for buprofezin and untreated control plots. Spraying for Lygus in late-July had little effect on host and parasitoid abundance or percentage parasitism. |
