Rust mites can be a nuisance pest and require careful monitoring and assessment. Check out the post below written by Dr. Patty Skinkis, Viticulture Extension Specialist & Associate Professor, which provides information on how to deal with these pests.
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Monitoring Vineyards for Grape Rust Mites in Late Summer
Dr. Patty Skinkis, Viticulture Extension Specialist & Associate Professor
Grape rust mites have been a nuisance pest in vineyards of western Oregon for years. They can be found living on grape tissues from early spring through summer. During late summer and into fall, they retreat to overwintering sites in the bark and bud scales. The grape rust mite has been known to cause shoot deformity early in the growing season and stippling of leaves as they advance into the upper canopy in summer. If populations are very high (hundreds to thousands per fully expanded leaf), the leaf tissue can begin to discolor, starting to turn a dark green, then purplish and finally a bronzed color in late summer to early fall. This discoloration can lead to reduced photosynthetic ability of the vines if a large percentage of the vine’s leaf area is damaged.
Monitoring for signs and symptoms of rust mite infestation are important to do throughout the season. However, determining the presence of grape rust mites in your vineyard now (late August and early September) will help determine whether control methods are warranted the following season. We developed a user-friendly method by which to monitor grape rust mites on vine tissues, and this method has since been employed by growers in Oregon to determine presence of rust mites. The protocol for this method is available for use:
- Grape tissue washing protocol (link to document)
- Visual work flow of protocol (link to document)
Using this method, we were able to determine a strong correlation of stippling symptoms to rust mite presence on small shoots and leaves. The greater the stippling severity on the leaf, the greater the number of rust mites. The bronzing of leaves was also associated with high rust mite numbers, but the symptom was associated with feeding later in the summer on older leaf tissues. Now is your last chance to monitor your vineyards for these symptoms and verifying mite presence before the hustle of harvest. For examples of these symptoms, see the grape rust mite section of the PNW Insect Management Handbook.
If you find significant rust mite damage and presence, it is best to make note of those vineyard blocks that are most damaged and consider your management options for the future. In some cases, you may want to reevaluate your in-season fungicide program, as sulfur has been found to be effective at reducing or maintaining low rust mite populations. Also, it is best to know the infestation status of your vineyard now so that plans can be made to monitor and take action against rust mites shortly after bud break the following spring. Current recommendations exist for early season rust mite control, and those can be found in the pest management guide released by OSU Extension each spring.
For more information about monitoring for rust mites and management, see the following publications and resources:
Schreiner, R.P., P.A. Skinkis, and A.J. Dreves. 2014. A rapid method to assess grape rust mites on leaves and observations from case studies in Western Oregon vineyards. HortTechnology. 24: 38-47.
Skinkis, P.A., J.W. Pscheidt, E. Peachey, A. Dreves, V.M. Walton, D. Sanchez, I. Zasada, and B. Martin. 2014. 2014 Pest Management Guide for Wine Grapes in Oregon. OSU Extension Publishing. http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/45975/em8413.pdf
Skinkis, P. 2014. Grape Rust Mites, eXtension/eViticulture.org. http://www.extension.org/pages/33107/grape-rust-mite#.U_yZCHcXOVo
Skinkis, P., J. DeFrancesco, and V. Walton. 2014. Grape Rust Mite, PNW Insect Management Handbook. http://insect.pnwhandbooks.org/small-fruit/grape/grape-grape-rust-mite
