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  • Author or Editor: Raymond Cloyd x
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Greenhouse managers tank mix pesticides to broaden the spectrum of pest control, and reduce pesticide and labor costs. However, the effect of tank mixing an assortment of pesticides on efficacy to control pests has not been documented. This study assessed how tank mixing commercially available insecticides and miticides in two-, three-, and four-way combinations impacts the control of western flower thrips (WFT), Frankliniella occidentalis in greenhouse experiments and a laboratory bioassay. The pesticides screened were spinosad, abamectin, bifenazate, azadirachtin, and imidacloprid. Each pesticide was applied at the label-recommended rate. In the greenhouse experiments, transvaal daisy (Gerbera jamesonii) and lisianthus (Eustoma grandiflorum) flowers were inoculated with 25 adult WFT, and then flowers were sprayed with the designated treatments. After 72 hours, flowers were emasculated to assess the numbers of live and dead WFT. In the laboratory bioassay, chrysanthemum (Dendranthema grandiflora) leaf disks, treated with each pesticide and all tank mixes, were exposed to 15 adult WFT. The numbers of live and dead WFT were assessed after 48 hours. For all three experiments, no antagonistic tank mixes were identified. All treatments with spinosad, including the individual application and tank mixes, resulted in high mortality of WFT based on the numbers of live and dead WFT recovered. Our data suggest that tank mixes of spinosad with the other pesticides tested do not affect the efficacy of spinosad in controlling WFT. This information is important to greenhouse managers who want to tank mix pesticides and still control WFT in addition to the other plant-feeding arthropods found in greenhouses.

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Greenhouse trials were conducted in 2000-2001 to evaluate the indirect effects of insect growth regulators, whether stimulatory or inhibitory, on the egg production of female citrus mealybug [Planococcus citri (Risso)]. Green coleus [Solenostemon scutellarioides (L.) Codd] were infested with 10 late third instar female citrus mealybugs. The insect growth regulators kinoprene, pyriproxyfen, azadirachtin, buprofezin, and novaluron were applied to infested plants at both the high and low manufacturer recommended rates. Beginning two days after treatments were applied, plants were monitored daily to determine when female mealybugs began to oviposit. Individual mealybugs were removed from plants, placed into glass vials containing 70% isopropyl alcohol when female mealybugs started to oviposit, and dissected to determine the number of eggs. Overall, there were no consistent patterns to suggest that the insect growth regulators and different rates tested had any effect on the egg production of citrus mealybug females. Although, in one instance, the insect growth regulators kinoprene and pyriproxyfen actually lowered citrus mealybug egg production. In addition, the insect growth regulator buprofezin numerically increased female citrus mealybug egg production.

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Pesticide mixtures are commonly used by greenhouse producers to deal with the array of arthropod (insect and mite) pests encountered in greenhouses. Greenhouse producers tank mix pesticides due to convenience because it is less time consuming, costly, and labor intensive to mix together two or more pesticides into a single spray solution and then perform one spray application compared with making multiple applications. Pesticide mixtures may also result in improved arthropod pest control. However, there has been no quantitative assessment to determine what pesticide mixtures (two-, three-, and four-way combinations) are being adopted by greenhouse producers and why. As such, a survey was conducted by distributing evaluation forms in conjunction with three sessions at two greenhouse producer conferences (two in 2007 and one in 2008) to obtain data on the types of pesticide mixtures used by greenhouse producers and determine if there are any problems associated with these pesticide mixtures. The evaluation form requested that participants provide information on the four most common pesticide mixtures (insecticides and/or miticides) used and for what specific arthropod pests. The response rate of the evaluation forms was 22.5% (45/200). The two-way pesticide mixture that was cited most often (n = 8) was the abamectin (Avid) and bifenthrin (Talstar) combination. The two pesticides typically included in a majority of the two-way and three-way mixtures were spinosad (Conserve) and abamectin. Spinosad was a component of 17 two-way and 7 three-way combinations, while abamectin was cited in 15 two-way and 9 three-way combinations. Both products are labeled for control of the western flower thrips (Frankliniella occidentalis), which is one of the most important insect pests in greenhouses. One pesticide mixture that was difficult to interpret involved the fungicides, thiophanate-methyl (Cleary's 3336) and metalaxyl (Subdue). This mixture was cited twice, and the arthropod pest listed was thrips (Thysanoptera). However, both fungicides have no insecticidal activity. Two of the mixtures listed in the survey used pesticides with similar modes of action: acephate (Orthene) + methiocarb (Mesurol), and pyrethrins (Pyreth-It) + bifenthrin (Talstar). A number of the pesticide mixtures listed for spider mites (Tetranychidae) were questionable due to similar life stage activity of the a.i. as indicated on the label including fenpyroximate (Akari) + clofentezine (Ovation), abamectin + chlorfenapyr (Pylon), and bifenazate (Floramite) + etoxazole (TetraSan). In fact, 38% of pesticide mixtures cited for twospotted spider mite (Tetranychus urticae) control should have been avoided due to analogous life stage activity. The data obtained from the survey clearly demonstrates that greenhouse producers implement a wide-range of pesticide mixtures to deal with the multitude of arthropod pests in greenhouses. However, the basis by which greenhouse producers decide the types of pesticides to mix together is not known. As such, the survey data can be used to direct future multistate or multiregional extension (outreach) efforts in developing programs specifically designed to educate greenhouse producers on which pesticides should and should not be mixed together.

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The way extension specialists and educators conduct programs, such as workshops, and transfer information to their designated clientele, including homeowners, professionals, and specialty groups, has changed within the last decade due to merging departments, budget cuts, reduced operating funds, and lack of refilling vacant positions. These factors have resulted in a number of driving forces that influence the way extension specialists and educators perform their duties, such as accountability, regionalization of extension, impact of technology, and expanding expertise. To be accountable under today's standards, extension specialists and educators must document the impact, relevance, and effectiveness of their programs. Required documentation must include economic, environmental, and human development factors. The effect of downsizing in many states has led to regionalization, which involves sharing extension specialists and educators across state boundaries. Although there are concerns, such as funding issues and evaluation of extension specialists and educators among states, regionalization in general has resulted in collaborative efforts to organize workshops and produce regional publications that serve a wider clientele base. Extension specialists and educators need to use computer-based and electronic technology, such as teleconferencing and distance-education, to present effective programs and address a wider audience, which will reduce the amount of required travel time. Finally, extension specialists and educators need to keep abreast of issues, such as invasive species, and develop programs to increase awareness of the economic and ecological impacts of invasive species in order to effectively serve the clientele base. Extension specialists and educators will more effectively serve their clientele, justify the importance of extension programming, demonstrate extension as a valued resource to administrators, and deal with the challenges of financial constraint existing now and in the foreseeable future by documenting impact, using multi-state programming, adopting new technology, and keeping up with current issues.

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A greenhouse study was conducted from Oct. 1999 through Feb. 2000, and Mar. 2001 through Apr. 2001, to determine the potential phytotoxic effects of selected insecticides on Spanish lavender (Lavandula stoechas L.), oregano (Origanum vulgare L. `Santa Cruz'), rosemary (Rosmarinus officinalis L.), St. Johnswort (Hypericum perforatum L. `Topaz'), wolly thyme (Thymus vulgaris L. `Wolly'), and nutmeg thyme (Thymus vulgaris L. `Nutmeg'). Insecticides used for the study were Beauveria bassiana Strain GHA, pyrethrin [+ piperonyl butoxide (PBO)], azadirachtin, potassium salts of fatty acids, two rates of cinnamaldehyde, paraffinic oil, and capsaicin. Visual observations of phytotoxicity were made 7 days after the final application. Pyrethrin, potassium salts of fatty acids, and both rates of cinnamaldehyde were consistently more phytotoxic than the other insecticides. Despite the phytotoxic effects from some of the insecticides, new growth that emerged following treatments compensated for the initial damage, and the herbs were still saleable.

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Fungus gnats (Bradysia spp.) are major insect pests in greenhouses. The adult stage is primarily a nuisance whereas the larval stage is directly responsible for plant injury by feeding on plant roots or tunneling into stems. Insecticides are used to deal with fungus gnat larvae in growing medium, although sometimes with limited success. This study evaluated the potential of using a soil amendment—diatomaceous earth (DE) incorporated into growing media—for controlling the fungus gnat Bradysia sp. nr. coprophila. Two experiments were conducted by testing a series of growing media containing various concentrations of diatomaceous earth, and several without diatomaceous earth. The effects of the growing media containing diatomaceous earth on both the 2nd and 3rd instars of fungus gnat larvae were determined by recording the number of adults captured on yellow sticky cards (2.5 × 2.5 cm). Based on the results obtained from both experiments, the addition of DE to growing medium, at the concentrations tested, did not negatively affect or increase efficacy against both the 2nd and 3rd instars. This suggests that incorporating DE into commercially available growing medium may not be beneficial to greenhouse producers. However, further research is needed to assess whether differential larval susceptibility and moisture content influence the ability of DE to control soil-dwelling arthropods.

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