Ministry of Agriculture
Grape Insect and Mite Pests
Grape Erineum Mite
(= Grape Leaf Blister Mite, Colomerus vitis (Pagenstecher))
- 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.
Identification
Adult erineum mites are only 0.2 mm long and a dissecting microscope is required to observe them properly. Their creamy pale bodies are elongate with only two pairs of legs. Although erineum galls can be confused with certain fungal diseases or phylloxera leaf galls by inexperienced growers, their characteristic appearance is the best way to identify these pests. The hemispherical concave galls or erinea formed on the undersides of leaves initially have a felty white appearance due to the presence of densely packed long leaf hairs. Opposite to these galls, bumps will be visible on the upper surfaces of leaves. These swellings are a reddish colour in spring and turn green as the leaves mature. Small numbers of mites feed on the dense hairs in each gall, which eventually turn brown. Having been reported recently from Washington State, two other forms of erineum mite, the leaf-curling strain and bud-inhibiting strain are possible in British Columbia. The former causes slight to severe downward curling of leaves in summer with stunting of shoots and increased growth of lateral shoots. Feeding of the bud-inhibiting strain on buds causes a range of abnormalities, including scarified shoots, short zigzagging internodes, dead terminal buds and malformed leaves. For additional information on erineum mites and other pests of grapes, visit the University of California Integrated Viticulture Online website.
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| Grape erineum mite damage to upper leaf surface | Grape erineum mite damage to lower leaf surface |
Life Cycle and Damage
Adult erineum mites overwinter under the scales of buds. Mites move in spring to developing shoots and create galls on young leaves around the fruiting zone. Several generations are produced each year, with new galls developing higher up the shoots. Beginning in late summer, adult mites move back to the buds for winter.
Leaves with a few too many erineum galls appear to function normally and there is little or no economic damage to mature vines until almost all leaves are covered with galls. Even then, damage usually only occurs if vines are also suffering from other stresses. Establishment of newly planted vines can be delayed somewhat by erineum mite feeding, which will retard or reduce fruiting.
Monitoring and Spray Thresholds
Erineum galls are usually very apparent during routine vineyard operations. Grape varieties differ in susceptibility to this pest and it is important to check individual blocks for the presence of mites. In order to prevent premature loss of leaves, new vines should be inspected and treatments applied if large numbers of galls are found on most leaves during the spring or summer months.
Biological Control
The western predatory mite, Galendromus occidentalis, is an important erineum mite predator. Predaceous thrips will feed on exposed mites, but their effectiveness is likely limited when mites are protected within the dense hairs of the galls.
Cultural Control
New plants may become infested in the nursery. Ensure that material used to establish new vineyards is free of mites and other pests or diseases. Removing galled leaves can control light infestations to some extent. Research conducted in the Okanagan Valley demonstrated that removal of infested leaves in May from Sauvignon Blanc vines did not alter yields or fruit quality.
Chemical Control
Erineum mite is seldom a problem in vineyards where sulphur is applied routinely for powdery mildew control. Applications of sulphur (e.g. Kumulus™ DF, or wettable sulphur) are most effective early in the season when galls are first being formed on new leaves. Sulphur sprays should not be used on Foch or Vitis labrusca varieties, as they are susceptible to leaf and fruit damage. Miticides (acaricides) such as Pyramite™ or Kelthane™ applied against spider mites and sprays of organophosphates (e.g. malathion and Sevin™) for control of leafhoppers will also reduce numbers of erineum mite somewhat.
September 2010
