Grape rust mite is best known from
grape-growing areas in Europe, South America, Australia and the
Pacific Northwest. This eriophyid mite is very small and
probably won't be seen without magnification. Body length is about 0.1-0.2 mm (1/100 inch).
Adult females overwinter beneath bud scales, under bark, and other
protected locations. They disperse to foliage in the
spring. Feeding by grape rust mite can seriously damage
spring growth and buds, resulting in reduced yield. Feeding
on leaf surfaces may cause leaves to turn dark green to black or
bronze. Foliage should be examined under a dissecting
microscope to evaluate mites because of their tiny size.
Summer populations may reach very high levels, but may not cause
much real damage to the vines; control may be needed the following
spring however, to prevent injury to buds and shoots (James
2019). The presence of some grape mites may actually
improve stability of biological control of spider mites by
providing additional prey for predatory mites.
Biological control: Control may be provided by
predatory mites. Growers are encouraged to use pesticides
that have low toxicity to these valuable predators (also control
agents for spider mites).
Chemical control: In commercial vineyards (OSU
2019), delayed dormant populations may be controlled by
sulfur at the woolly bud stage, followed by a spray at bud break (Skinkus
2019). Spring and early summer populations may be
controlled using insecticidal soap, neem oil, Stylet oil, or
sulfur. Late summer - fall populations may be difficult to
control because mites may have started their movement to
overwintering sites beneath bud scales.
