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Augusto Ramírez-Godoy, María del Pilar Vera-Hoyos, Natalia Jiménez-Beltrán and Hermann Restrepo-Díaz

with imidacloprid (Confidor ® 350 SC; Bayer, Bogotá, Colombia) at 0.10 L a.i. per ha; and 3) trees treated with a commercial strain of B. bassiana (spores of the GHA strain) (Mycotrol ® ; Laverlam S.A., Cali, Colombia). A conidial germination

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Charles A. Powell, Mark A. Ritenour and Robert C. Bullock

, the causal agent of citrus canker ( Hill, 1918 ). Two of the most commonly used insecticides on young trees are Temik (aldicarb) and Admire (imidacloprid). Both Temik ( Bullock, 1989 ; French and Timmer, 1979 ) and Admire ( Powell et al., 2006 , 2007

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Michelle L. Bell

Rooted `Freedom' poinsettia cuttings were treated with imidacloprid by surface application (0.005 g a.i./16.5-cm container) and the following alternative application techniques: foliar spray, 10 s dip, and 1 h dip (0.028 g a.i./liter). Topdressed plants were either overhead- or bottom-watered to investigate effects of leaching on imidacloprid residual activity. Number of silverleaf whitefly nymphs/cm2 leaf were counted weekly, then biweekly, from 14 to 112 days after treatment. Spray and dip applications delayed establishment of heavy whitefly populations compared to the untreated control but did not prevent infestation. Single foliar and dip applications of imidacloprid proved not to be viable control alternatives. The two irrigation treatments using surface-applied imidacloprid provided whitefly control through 84 days after treatment. Beyond 84 days after treatment, topdressed, subirrigated plants had more whiteflies than topdressed, overhead-irrigated plants.

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Justin M. Vitullo and Clifford S. Sadof

plant substrates. Imidacloprid is one of the most commonly used materials in landscapes because of its activity against leaf beetles (Chrysomelidae) and its long residual toxicity ( Sclar and Cranshaw, 1996 ; Webb et al., 2003 ). A single systemic

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Adam D. Karl, Ian A. Merwin, Michael G. Brown, Rebecca A. Hervieux and Justine E. Vanden Heuvel

of pesticides such as imidacloprid in the vineyard. Imidacloprid leaching is lower in soils with greater organic matter due to the sorption of imidacloprid to organic matter, providing a potential means of reducing leaching ( Cox et al., 1998

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Charles A. Powell, Michael S. Burton, Robert Pelosi, Mark A. Ritenour and Robert C. Bullock

); an annual application of oxydemeton-methyl (Metasystox-R; Gowan Co. Yuma, AZ) (trunk drenched, 0.62 mL·L −1 ); soil drenches with imidacloprid (1-[(6-chloro-3-pyridinyl) methyl]-N-nitro-2-imidazolidinimine) (Admire; Bayer Cropscience) at 1920 mg

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Claudio C. Pasian, Daniel K. Struve and Richard Lindquist

The effectiveness of two methods of application of the insecticide imidacloprid in controlling 1) aphids (Brachycaudus helichrysi) on Chrysanthemum plants, Dendranthema ×grandiflora (Ramat) (cv. Nob Hill) and 2) whitefly (Bemisia argentifolii) on poinsettia, Euphorbia pulcherrima (Wild.) (cv. Freedom Red) were compared. Plants were grown in containers with their interior covered by a mixture of flat latex paint and several concentrations of imidacloprid (0, 10, 21, 42, and 88 mg·L–1), or treated with a granular application of the insecticide (1% a.i.) according to label recommendations. All imidacloprid treatments were effective in reducing aphid survival after 8 weeks. The two most effective treatments were: granular (1% a.i.) and 88 mg·L–1 with an average of 0.2 aphid per plant as opposed to 50.4 aphids per plant for the control. The 42-mg·L–1 treatment had an aphid survival rate 1.6 aphids per plant. All imidacloprid treatments were effective in reducing white fly larvae. The 42 and 88 mg·L–1 and the granular (1% a.i.) were equally effective in reducing larvae numbers in lower poinsettia leaves: 0.5, 1.9, 0.9 larvae/2.5 cm leaf disk, respectively, while the control treatment had 62.9. None of the plants given treatments with paint showed any sign of phytotoxicity. These results suggest the possibility of a new application method for systemic chemicals with the potential of reducing or eliminating Worker Protection Standard (WPS) Restricted Entry Intervals (REI) and reducing the release of chemicals to the environment. Chemical name used: 1-[(6-Chloro-3-pyrimidil)]-N-nitro-2-imidazolidinimine.

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Gregory J. McKee, Frank G. Zalom and Rachael E. Goodhue

rates applied, and their application dates are listed in Table 1 . Table 1. Experimental treatments applied to strawberries at Watsonville, Calif., 2002–2003. Products used as experimental treatments included imidacloprid (Admire

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Marc van Iersel and Ron Oetting

Ebb-and-flow systems can be used to apply systemic pesticides to greenhouse crops without worker exposure or runoff. However, there is little information on the efficacy of pesticides applied with ebb-and-flow systems. We are using silverleaf whitefly (Bemisia argentifolii) control on poinsettia (Euphorbia pulcherrima) with imidacloprid as a model system to study pesticide efficacy in ebb-and-flow systems. The objective of this study was to determine the effect of the amount of insecticide taken up by the pot on the efficacy of whitefly control. Different amounts of imidacloprid uptake were obtained by not watering the plants for 0, 1, 2, or 4 days before the imidacloprid application. The imidacloprid (132 g·L–1) was applied once when the roots of the cuttings had reached the side of the pots. These treatments were compared to an untreated control on ebb-and-flow and a standard drench application (100 mL) to hand-watered plants. Pots in the different subirrigation treatments absorbed 12 to 175 mL of imidacloprid solution. Four days after the application, leaf tissue of the hand-watered plants contained 8 to 20 times more imidacloprid than the subirrigated plants. Efficacy was determined from the percentage of surviving mature whiteflies after 2 days on the plants and by counting the number of immatures after 2 weeks. Surprisingly, imidacloprid efficacy was better in the subirrigated imidacloprid treatments than in the hand-watered treatment. Whitefly control in all subirrigated imidacloprid treatments was excellent, irrespective of the amount of imidacloprid solution taken up by the pots.

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J.C. Palumbo and C.A. Sanchez

Imidacloprid is a new, chloronicotinyl insecticide currently being used to control sweetpotato whitefly [Bemisia tabaci Genn, also known as silverleaf whitefly (Bemisia argentifolii Bellows and Perring)]. Large growth and yield increases of muskmelon (Cucumis melo L.) following the use of imidacloprid have caused some to speculate that this compound may enhance growth and yield above that expected from insect control alone. Greenhouse and field studies were conducted to evaluate the growth and yield response of melons to imidacloprid in the presence and absence of whitefly pressure. In greenhouse cage studies, sweetpotato whiteflies developed very high densities of nymphs and eclosed pupal cases on plants not treated with imidacloprid, and significant increases in vegetative plant growth were inversely proportional to whitefly densities. Positive plant growth responses were absent when plants were treated with imidacloprid and insects were excluded. Results from a field study showed similar whitefly control and yield responses to imidacloprid and bifenthrin + endosulfan applications. Hence, we conclude that growth and yield response to imidacloprid is associated with control of whiteflies and the subsequent prevention of damage, rather than a compensatory physiological promotion of plant growth processes. Chemical names used: 1-[(6-chloro-3-pyridinyl)methyl]-4,5-dihydro-N-nitro-1-H-imidazol-2-amine (imidacloprid); [2 methyl(1,1′-biphenyl)-3yl)methyl 3-2-chloro-3,3,3-trifluoro-1-propenyl]-2,2-dimethylcyclopropane carboxylate (bifenthrin); 6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodiaxathiepin 3-oxide (endosulfan).