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United States Department of Agriculture

Agricultural Research Service

Title: Low-Density Releases of Neoseiulus Fallacis to Control Tetranychus Urticae (Acari: Phytoseiidae, Tetranychidae): Achieving Near-Equilibrium Predator: Prey Densities, and Maximum Dispersal of Predator Mites in Apple Seedlings

Authors
item Croft, Brian - OREGON ST. UNIVERSITY
item PRATT, PAUL
item Luh, Han - OREGON ST. UNIVERSITY

Submitted to: Experimental and Applied Acarology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 20, 2003
Publication Date: July 20, 2004
Citation: Croft, B.A., Pratt, P.D., Luh, H.K. 2004. Low-density releases of neoseiulus fallacis to control tetranychus urticae (acari: phytoseiidae, tetranychidae): achieving near-equilibrium predator: prey densities, and maximum dispersal of predator mites in apple seedlings. Experimental and Applied Acarology.

Interpretive Summary: Releases of the predatory mite Neoseiulus fallacis at 1,500-6,000 per ha when densities of the two spot spider mite were at extremely low densities (0.1-0.3 per leaf) provided seasonal control of all stages of the pest mite (Tetranychus urticae) at 1-2 per leaf in an apple seedling rootstock nursery. Predaceous mites (all stages) increased to 0.3-0.4. per leaf after releases and predator: prey ratios of plus or minus 1:3-7 provided pest regulation thereafter. Such low-density releases were thought to be effective because multiple dispersal bouts allowed predators to locate rare and widely distributed spider mites (on 2-6% of leaves). A mathematical model simulating predator dispersal (incorporating wind speed and direction) described the movement and pest control patterns accurately when compared to field collected data. An upright, dense, uniform planting of apple seedlings was an effective producer and recipient for dispersing predators and these attributes seemed to explain why biological control was so effective. Low-density releases of N fallacis for control of T. urticae are predicted to be less effective on other crops with less prominent profiles and soil coverage.

Technical Abstract: Releases of Neoseiulus fallacis (Garman) at 1,500-6,000 per ha when prey were at 0.1-0.3 per leaf provided seasonal control of Tetranychus urticae Koch (all stages) at 1-2 per leaf in an apple seedling rootstock nursery. Predaceous mites (all stages) increased to 0.3-0.4. per leaf after releases and predator: prey ratios of plus or minus 1:3-7 provided pest regulation thereafter. Such low-density releases were thought to be effective because multiple dispersal bouts allowed predators to locate widely distributed spider mites (on 2-6% of leaves). A random-diffusion model simulating predator dispersal (incorporating wind speed and direction parameters) adequately explained movement and pest control patterns. An upright, dense, uniform planting of apple seedlings was an effective producer and recipient for dispersing predators and these attributes seemed to explain why biological control was so effective. Low-density releases of N fallacis for control of T. urticae are predicted to be less effective on other crops with less prominent profiles and soil coverage.

Last Modified: 8/19/2014
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