Compatibility of insect growth regulators with Eretmocerus eremicus (Hymenoptera : Aphelinidae) for whitefly (Homoptera : Alyerodidae) control on poinsettias II. Trials in commercial poinsettia crops

The efficacy and cost of reduced release rates of the parasitoid Eretmoceru s eremicus Rose and Zolnerowich (Hymenoptera: Aphelinidae) when combined wi th application of the insect growth regulator buprofezin were compared to t hose of a higher parasitoid release rate used alone for whitefly control (H omoptera: Aleyrodidae) on poinsettia (Euphorbia pulcherrima Willd. ex Koltz .). The trial was conducted in seven greenhouses in Methuen, Massachusetts from August through December 1997 and employed commercial poinsettia produc tion practices. Two whiteflies species, Trialeurodes vaporariorum (Westwood ) and Bemisia argentifolii Bellows and Perring (= Bemisia tabaci [Gennadius ] strain B), were present. Three treatments were examined: (1) E. eremicus used alone at a release rate of three females per plant per week (two green houses); (2) E. eremicus at an intermediate release rate of two females per plant per week, combined with mid-season use of buprofezin (two applicatio ns, spaced 1 week: apart, applied in weeks 9 and 10) (two greenhouses); and (3) E. eremicus at a low release rate of one female per plant per week, co mbined with mid-season use of buprofezin, applied as in treatment 2 (two gr eenhouses). In addition, observations were made in one additional greenhous e at the site, in which the grower used pesticides for whitefly control. Pr ior to the start of the trial, cuttings used for all treatments experienced some pesticide use, first abamectin during rooting and later buprofezin at potting to reduce whitefly numbers, which were initially very high. At har vest, densities of live whitefly nymphs were not statistically different am ong the biological control treatments, indicating that a low parasitoid rel ease rate combined with buprofezin was as effective as a higher release rat e of the parasitoid used alone. Nymphal densities in separate market sample s (based on smaller sample sizes) showed differences among treatments, but all treatments, including the low parasitoid release rate + buprofezin main tained densities of live nymphs + pupae at or below approximately two per l eaf, a level commercially acceptable in local markets. Control costs per si ngle-stemmed poinsettia plant were $1.18 for the high parasitoid release tr eatment, $0.75 for the treatment of meekly releases of two female parasitoi ds per plant per week + buprofezin, $0.38 for the treatment of releases of one female parasitoid per plant per week + buprofezin, and $0.14 for the ch emical control greenhouse, (C) 2000 Academic Press.