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Michelle L. Bell and James R. Baker

Twenty-eight greenhouse screening materials, with predetermined airflow resistance values, were evaluated for exclusion of silverleaf whitefly (Bemisia argentifolii Perring & Bellows) and thrips from a mixed-species population. Screens differed in exclusion efficacy, as a percentage of the fiberglass window screen control and at an approach velocity of at 92 m/min, from –35 to 94% for silverleaf whitefly and from –13 to 95% for thrips. Seventeen screens excluded more silverleaf whitefly, whereas seven excluded more thrips than the window screen control. One material differentially excluded whitefly over thrips; many more differentially excluded thrips over whitefly. Airflow resistance, indicative of mesh hole size, did not necessarily correspond with degree of exclusion. Though two high-resistance screens, No-Thrips and Econet S, excluded both pests, not all materials characterized as highly resistant to airflow provided significant exclusion. Exclusion of both pests was also attained with three moderate resistance screens, BugBed 123, BugBed 85, Pak 44×44, and one low-resistance screen, BugBed 110UV.

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Michelle L. Bell, James R. Baker, and Douglas A. Bailey

Potential phytotoxicity and plant growth-regulating activity of insecticidal dips for poinsettias was investigated by dipping, then growing unpinched, rooted cuttings of `Red Sails', `Freedom', and `V-14 Glory' in the following insecticidal emulsions for five durations: 2% insecticidal soap (Safer's), 2% horticultural oil (Sunspray Ultrafine), fluvalinate (Mavrik Aquaflow), oxythioquinox (Joust), kinoprene (EnstarII), azadirachtin (Margosan-O), fenoxycarb (Precision), and an oil-carrier formulation of Beauveria bassiana (Naturalis-L). Dips in soap, oxythioquinox, Naturalis-L, and oil were phytotoxic to all three cultivars. Also, kinoprene and fenoxycarb were phytotoxic to `Red Sails'. At dip durations of 10 s and greater, soap, Naturalis-L, and oil were phytotoxic. Oxythioquinox was phytotoxic at durations of 1 min, 15 min, and 1 h. Only fluvalinate was not phytotoxic as a 4-h dip. After 2 weeks, plants dipped in oxythioquinox, Naturalis-L, and oil were stunted. By week 4, differential cultivar effects were seen: six dips (all but fluvalinate and azadirachtin) stunted growth of `Red Sails', whereas only Naturalis-L and oil retarded growth of `V-14 Glory'. Six weeks after treatment, growth of all cultivars was stunted by oxythioquinox, Naturalis-L, and oil, but was not retarded by fluvalinate or azadirachtin. Dip duration significantly affected growth by weeks 4 and 6, when all durations of Naturalis-L and oil reduced growth. Additionally, 4-h dips of oxythioquinox and kinoprene stunted plants after 4 weeks, and 1- and 4-h dips of oxythioquinox, kinoprene, and fenoxycarb adversely affected growth after 6 weeks.

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Michelle L. Bell, James R. Baker, and Douglas A. Bailey

Since whiteflies preferentially oviposit on the newest leaves, it is the early life stages that are most likely to be present on poinsettia cuttings from infested stock or infested during rooting. This study evaluated efficacy of insecticidal dips against eggs and first nymphal instars of the silverleaf whitefly, Bemisia argentifolii. Dip efficacy was investigated by dipping rooted cuttings of whitefly-infested `Freedom' in the following insecticide emulsions: 2% insecticidal soap (M-Pede), 1% horticultural oil (Ultrafine), fluvalinate (Mavrik), oxythioquinox (Joust), kinoprene (EnstarII), azadirachtin (Margosan-O), fenoxycarb (Precision) and imidacloprid (Merit). Two dip durations, 10 seconds and 1 hour, were tested for each insecticide. Water dips for the two durations were used as control treatments. Fenoxycarb and azadirachtin dips for durations of 10 seconds and 1 hour and oxythioquinox dips for 1 hour resulted in greater egg mortality than the other treatments. No insecticide/dip duration treatment gave 100% mortality of eggs. Dips found to be efficacious killed proportionately fewer eggs than first instar nymphs.