Ministry of Agriculture
Grape Insect and Mite Pests
Grape Leaf Rust Mite
(Calepitrimerus vitis (Nalepa))
- Identification
- Life Cycle and Damage
- Monitoring and Spray Thresholds
- Biological Control
- Cultural Control
- Chemical Control
Prepared by D. Thomas Lowery, Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, Summerland.
Grape leaf rust mite, which belongs to the same family (Eriophyidae) as grape erineum mite, was identified for the first time on grapes in the Okanagan Valley in 2009. Growers are referred to the following source for additional information: Grapevine pests and their management, by A. Loch. Primefact 511, New South Wales Dept. of Primary Industries, NSW Australia.
Identification
A microscope is required to properly identify these 0.2 mm long pale white wormlike mites that closely resemble erineum or blister mites, but do not form leaf galls. They are much smaller than spider mites and elongate rather than round, tapering at the rear, and having two pair of legs near the head. Their presence is best determined by the bronzing of leaves during July and August that results from their feeding. Unlike spider mites that cause similar damage to leaves, grape leaf rust mites do not produce webbing.
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| Grape leaf rust mites. Photo courtesty: M. Weis, Agriculture and Agri-Food Canada, Summerland |
Enlarged grape leaf rust mite. Photo courtesty: M. Weis, Agriculture and Agri-Food Canada, Summerland |
Life Cycle and Damage
Adult rust mites that spend the winter under bark or bud scales move in spring to the developing buds to feed and lay eggs. Large numbers of adults concentrated on the available green tissue in early spring can damage buds, resulting in deformed leaves, scarring of shoots, reduced shoot growth, and even bud death. Early season rust mite damage can be confused with cold injury or damage from other causes. Damage becomes less visible as the season progresses and shoots lengthen. Immature mites that hatch over a period of several weeks feed under the bud scales, eventually moving to feed on developing leaves. Unlike spider mites, rust mites infest equally the upper and lower leaf surfaces. Many generations are produced throughout the summer, and before leaves drop in the fall adult rust mites migrate to the cordon and trunk for the winter. Bronzing of leaves is most obvious during July and August, but damage to leaves is not thought to cause serious damage to the vines. Extensive bronzing of leaves is an indication that rust mites need to be controlled the following spring.
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Grape leaf rust mite damage to shoots. Photo courtesy: L. Jensen, Agriculture and Agri-Food Canada, Summerland |
Monitoring and Spray Thresholds
There are no established thresholds for this pest. Control is indicated when a significant proportion of leaves become bronzed in late summer.
Biological Control
As for erineum mite, western predatory mite, Galendromus occidentalis, other mite predators, and predacious thrips are often able to keep rust mites in check. To maintain healthy populations of beneficial insects and predatory mites, it is important whenever possible to limit the use of insecticides and to apply selective materials that are less toxic to predatory mites.
Chemical Control
A successful rust mite control program developed in Australia relies largely on spring applications of sulphur (e.g. Kumulus™ DF, or wettable sulphur) in high volume sprays during bud swell to woolly bud stage. Sulphur sprays should not be used on Foch or Vitis labrusca varieties, as they are susceptible to leaf and fruit damage. There are no miticides currently registered for the control of grape leaf rust mite.
September 2010
