Phenology and control of rust mites on grapevines

Rust mite-related, Calepitrimerus vitis (Nalepa 1905) (Acari: Eriophyidae) Short Shoot Syndrome (SSS) is described in many grapegrowing areas worldwide. Symptoms include leaf distortion or crinkling, stunting of young growing shoots, railroad scarring on shoot stems, bronzing on leaves in the fall, zig-zag shaped shoots, reduced cluster size and yield. Most vineyards generally have rust mites. Research indicates that the early part of the growing season is most probably when damage happens. This susceptible period is when buds start to swell and tissues are less tightly packed until budbreak. Long-term heat accumulation maps of vineyard regions indicate when vines are susceptible to early-season damage by C. vitis. As the season progress, mites move from protected overwintering refuges to exposed positions on vine tissues and leaves. In-season mite populations spread across the canopy until mid-July. The peak population of rust mites on leaves was recorded end of July and the first half of August. Mite populations start to decrease on vine leaves later in August and continue to decrease until after harvest in October. Rust mites collected from sticky tapes in middle August through early October indicate that during this time, mites are most likely moving to overwintering sites.

The current recommendations for rust mite control is during the late dormant period up to bud break as explained above. Our phenology data indicates that there may be additional timing and pesticides options and these are discussed.