| Results from sampling adult whiteflies in greenhouses using yellow sticky traps indicated that a minimum of one card per 37 m{dollar}{bsol}sp2{dollar} (one per 400 ft{dollar}{bsol}sp2{dollar}) should be considered for pest monitoring applications in poinsettia stock plants. This density, two-and-a-half times that presently recommended, is necessary due to population aggregation.; Potential phytotoxicity and plant growth regulating activity of insecticidal dips for rooted poinsettia cuttings was investigated. For insecticidal soap, 10 s and 1 min. dips did not inhibit growth of cultivars tested, and no dip duration proved inhibitory to cultivar Freedom. Ten second dips in oxythioquinox did not result in phytotoxicity or negative effects on growth of any cultivar. Fenoxycarb and kinoprene were phytotoxic and decreased growth only as 4 h dips to 'Red Sails'. Kinoprene decreased growth of 'V-14 Glory' as a 4 h dip. Fluvalinate and azadirachtin were not phytotoxic or inhibitory to growth of any cultivar at any duration, except azadirachtin which was slightly phytotoxic as a 4 h dip. In a separate study investigating efficacy of dips against early immature stages of the silverleaf whitefly, Bemisia argentifolii, only fenoxycarb decreased hatch rate. Oxythioquinox, imidacloprid, kinoprene and azadirachtin as 10 s and 1 h dips resulted in mortality of nymphs hatched from treated eggs. Soap and fenoxycarb killed hatched nymphs as 1 h dips only. Oxythioquinox and kinoprene provided the highest mortality of hatched nymphs as 1 h dips. Soap, oxythioquinox, azadirachtin, kinoprene and imidacloprid increased mortality of treated first-instar nymphs. Fluvalinate did not affect hatch rate or nymphal mortality. Another study combined chemical and cultural control to examine alternative applications and irrigation effects on the systemic insecticide imidacloprid. Spray and dip applications only slightly delayed establishment of heavy populations of silverleaf whitefly nymphs and proved non-viable as control alternatives. Surface-applied imidacloprid provided control until 84 days after treatment (DAT). By 84 DAT and continuing through 112 DAT, surface-application/subirrigated plants gained more whiteflies than did surface-application/overhead-irrigated plants.; In physical control studies, a wind tunnel was built to determine the airflow resistance of 28 commercial greenhouse screening materials. Resistance curves were generated by plotting pressure drops across each screen over a range of air approach velocities. Pressure drops ranged from 0.008 to 0.272 inch w.g. at an example air velocity of 300 ft./min. Five screens were characterized as very highly or highly resistant to airflow but many more screens had moderate or low resistance and were relatively similar in their pressure drops under production conditions. All moderate, low and very low resistance screens had pressure drops below 0.07 inch w.g. at 300 ft./min. giving the grower several options in choosing a screen that will not exceed an acceptable maximum pressure drop and thus maintain ventilation and cooling efficiency. In separate studies of screen efficacy, 17 screens excluded more silverleaf whitefly whereas only seven excluded more thrips than the fiberglass window screen control. FlyBarr differentially excluded whitefly over thrips; many more screens excluded thrips over whitefly. Not all materials characterized as highly resistant to airflow provided significant exclusion. Exclusion of both pests was attained with several moderate and one low resistance screen, BugBed 110UV. |
