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New Repellent Show Promise for Reducing Rodent Damage

Voles cause extensive girdling damage to orchards and vine crops in California. Although rodenticides are often used to control vole damage, they are rarely allowed in fields where fruit is on the trees for most of the year.

Repellents for rodents have shown promise in lab studies, but often fail to be effective in field trials. Recent laboratory studies have shown low concentrations of anthraquinone (AQ; a naturally occurring compound) can cause up to 84 percent repellency in voles exposed to AQ-treated grains. Vegetation management, such as mowing, herbicide application, or physical removal of vegetation around the base of trees, may also help reduce vole damage.

NWRC and University of California researchers investigated the efficacy of combining an AQ application with vegetation management to minimize vole girdling damage to Clementine citrus trees. Results showed a 90 to 100 percent reduction in girdling damage to trees following a single application of AQ during trials in spring and summer. Removal of vegetation around the base of trees further reduced damage during the summer, with no girdling observed on AQ-treated trees that were surrounded by bare soil. Furthermore, the efficacy of AQ did not decrease during the duration of the 5-6 week sampling period. Researchers recommend the use of AQ and vegetation management as part of an integrated pest management approach for mitigating vole damage in the summer. 

Other studies involving captive Richardson’s ground squirrels and house mice have shown AQ-treated materials may also help to reduce structural damage by these rodent species.

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