Journal of Economic Entomology (2009) 102, 336-346

George P. Opit, Jamis Perret, Kiffnie Holt, James R. Nechols, David C. Margolies and Kimberly A. Williams (2009)
Comparing chemical and biological control strategies for twospotted spider mites (Acari: Tetranychidae) in commercial greenhouse production of bedding plants
Journal of Economic Entomology 102 (1), 336-346
Abstract: Efficacy, costs, and impact on crop salability of various biological and chemical control strategies for Tetranychus urticae Koch (Acari: Tetranychidae) were evaluated on mixed plantings of impatiens, Impatiens wallerana Hook.f (Ericales: Balsaminaceae), and ivy geranium, Pelargonium peltatum (l.) L'Hér. Ex Aiton (Geraniales: Geraniaceae), cultivars in commercial greenhouses. Chemical control consisting of the miticide bifenazate (Floramite) was compared with two biological control strategies using the predatory mite Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae). Treatments were 1) a single, early application of bifenazate; 2) a single, early release of predatory mites at a 1:4 predator:pest ratio based on leaf samples to estimate pest density; 3) a weekly release of predatory mites at numbers based on the area covered by the crop; and 4) an untreated control. T. urticae populations were monitored for 3 wk after the earliest treatment. When plants were ready for market, their salability was estimated. Bifenazate and density-based P. persimilis treatments effectively reduced T. urticae numbers starting 1 wk after plants had been treated, whereas the scheduled, area-based P. persimilis treatment had little or no effect. The percentage of flats that could be sold at the highest market wholesale price ranged from 15 to 33%, 44 to 86%, 84 to 95%, and 92 to 100%, in the control, weekly area-based P. persimilis, bifenazate, and single density-based P. persimilis treatments, respectively. We have shown that in commercial greenhouse production of herbaceous ornamental bedding plants, estimating pest density to determine the appropriate number of predators to release is as effective and offers nearly the same economic benefit as prophylactic use of pesticides.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): George P. Opit, David C. Margolies

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
control - general
Research topic(s) for beneficials or antagonists:
evaluation - screening - selection
application technology

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Tetranychus urticae	Impatiens (crop)	U.S.A. (mid S)
	Tetranychus urticae	Pelargonium (crop)	U.S.A. (mid S)
Phytoseiulus persimilis (predator)	Tetranychus urticae	Impatiens (crop)	U.S.A. (mid S)
Phytoseiulus persimilis (predator)	Tetranychus urticae	Pelargonium (crop)	U.S.A. (mid S)