Grape erineum mite, Colomerus vitis (Pagenstecher)
This is taken primarily from an
extension bulletin by D. G. Pfeiffer & P. B. Schultz, entitled
"Major Insect and
Mite Pests of Grape in Virginia" (Va. Coop. Ext. Serv. 444-567 (1986))
This eriophyid mite is very small and probably
won't be seen without magnification.
It overwinters beneath loose bark of one-year old canes. There are
three strains reported: the bud strain, the erineum strain, and the
leaf-curling strain. Feeding by the bud strain on buds of
susceptible varieites injures the bud cluster, distorts basal leaves
(developing apical leaves are deeper in the bud, and are less likely to
be injured at this time), and may kill the overwintering buds. In
spring,
mites move to leaves where they cause a gall-like "erineum"
(mite-induced growth of leaf surface hairs or erinea) on the
upper leaf surface. On the lower surface, beneath the erineum, is
a dense, white growth of abnormally curled plant hairs. Mites feed
and reproduce in this patch of hairs.
Some varieties reportedly support populations fo grape erineum mite
without developing the leaf erineum symptom. Best time for
control is when shoots are growing or when erinea are forming.
When mites have retreated to beneath bud scales, control is difficult.
Other reading:
Jeppson, L. R., H. H. Keifer, & E. W. Baker. 1975. Mites Injurious
to Economic Plants.Univ. of Calif. Press, Berkeley.614 p. 74 pls.
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