Environmental Entomology (1991) 20, 104-109

Stephen C. Welter, Rachael Freeman and Delbert S. Farnham (1991)
Recovery of 'Zinfandel' grapevines from feeding damage by Willamette spider mite (Acari: Tetranychidae): Implications for economic injury level studies in perennial crops
Environmental Entomology 20 (1), 104-109
Abstract: Complete recovery of 'Zinfandel' grapevines from damage by Willamette spider mite, Eotetranychus willamettei (McGregor), required 2 yr. For vines that previously had experienced the highest level of mite damage (1,347 mite-days), a significant reduction of 14.9% in total yield per vine was detected within the first year of recovery. However, no significant reductions were noted in vegetative growth, mean berry size, or number of fruit clusters per vine (P > 0.05). Yield depressions after 2 yr of infestation were not greater than after a single year of infestation. No significant differences were found for any parameter measured within the second year of the study. A graphic model is presented to illustrate the potential effects of differential recovery rates and duration of recovery from damage by pests of perennial crops on the determination of economic injury levels. Increases in total recovery time and decreases in rate of recovery resulted in lower predictions for economic injury levels for fixed control costs. Failure to consider recovery rate and duration is hypothesized to result in the underestimation of crop losses due to indirect feeding damage.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)

Research topic(s) for pests/diseases/weeds:
damage/losses/economics

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Eotetranychus willamettei	Grapevine (Vitis)	U.S.A. (SW)