This study was designed to determine the efficacy of binary pesticide mixtures against one of the most important insect pests of greenhouse-grown horticultural crops, western flower thrips (Frankliniella occidentalis). Two separate experiments were conducted under greenhouse conditions to simulate a greenhouse production cycle using yellow transvaal daisy (Gerbera jamesonii) cut flowers, which were artificially infested with a known number of western flower thrips. The pesticides used in the two experiments were spinosad, pymetrozine, abamectin, pyridalyl, fluvalinate, chlorfenapyr, bifenazate, azadirachtin, petroleum oil, tolfenpyrad, fenhexamid, azoxystrobin, and spirotetramat. Pesticide mixtures were evaluated at the recommended labeled rates (Expt. 1) and assessments were made to determine if adding didecyl dimethyl ammonium chloride enhanced the efficacy of the pesticide mixtures (Expt. 2). Results from Expt. 1 indicated that many of the binary pesticide mixtures provided ≥80% mortality of western flower thrips although this was a baseline population without previous exposure to pesticides. In Expt. 2, the addition of didecyl dimethyl ammonium chloride failed to increase the efficacy of most of the designated pesticide mixtures compared with the pesticides applied separately. Furthermore, none of the binary pesticide mixtures were phytotoxic to the transvaal daisy flowers. Although there are issues associated with using pesticide mixtures such as the potential for resistance developing to different pesticides in mixtures, greenhouse producers combine pesticides together to reduce labor costs and expand the spectrum of activity against insect and mite (Tetranychidae) pests. Therefore, the relevance of this information is that greenhouse producers now understand which pesticide mixtures may be used and those that should be avoided when suppressing populations of western flower thrips thus minimizing feeding damage to greenhouse-grown horticultural crops.
Raymond A. Cloyd and Amy L. Raudenbush
Amy L. Raudenbush, Raymond A. Cloyd, and Erik R. Echegaray
This study was conducted to assess the direct and indirect effects of Growstones™ aggregates, which are made from recycled glass, on fungus gnat, Bradysia sp. nr. coprophila (Diptera: Sciaridae), adult emergence, female egg-laying capacity, and egg survival. A series of experiments were performed under laboratory conditions to evaluate the effect of different sizes (2.0 to 10.0 mm) of Growstones™ aggregates, layer thicknesses (0.63 to 3.18 cm), and the use of the biological control agent, the rove beetle, Dalotia coriaria, along with different thicknesses (1.27 and 3.18 cm) of small Growstones™ aggregates on fungus gnat adult emergence. For each experiment, Growstones™ aggregates were applied to the surface of the growing medium in 473-mL polypropylene deli containers. This study demonstrated that the thickest (3.18 cm) layer of small (2.0 mm) Growstones™ aggregates significantly reduced or delayed the emergence of fungus gnat adults. In addition, the thickest layer of small Growstones™ aggregates may have indirectly affected egg survival. However, the use of Growstones™ along with rove beetle adults did not significantly reduce fungus gnat adult emergence.