Maple Gall Mites
Contact: Eric Day, Manager, Insect Identification Laboratory
August 1996
Maple Gall Mites
Acarina: Eriophyidae, Eriophyes spp.
Plants Attacked
Silver, red, and sugar maple
Description of Damage
Growths in discreet gall formations are
incited by the feeding of adult mites on newly developing
foliage. Several species of mites are involved: green or red
maple bladder gall on silver and red maple; green to tan maple
spindle gall on sugar maple; and red maple erineum gall on silver
and red maple.
Identification
Not an insect, nor a typical spider mite, these
mites are seen with difficulty even through a 10X magnifier.
They are carrot-shaped or worm-like, whitish or orange, and have
2 pairs of very short legs.
Life History
Adult mites become active very early in spring as
buds begin to open. As new leaves unfold, mites begin to feed.
The leaf tissue at that point grows out from the upper surface to
form a gall gradually, enclosing the mite. As the leaves become
full size, the mites in the numerous galls lay eggs which hatch
in a very short time. Hundreds of mites develop, and leave the
galls through the opening on the underside of the leaf blade to
crawl to newly developing leaves. By the time new growth on the
plant ceases, little mite activity occurs until the next spring.
Control
There is little that can be done to prevent maple gall
mites. Sprays have some lessening effect, but little damage is
caused to the plant even in severe infestations. Control is
hardly worthwhile. Lime sulfur can be used as a spray before
leaf buds open, but while flowers are blooming. Caution: lime
sulfur causes severe staining of white paints, woodwork, and
stonework.
Remarks
This is probably one of the most common inquiries
received by diagnosticians because the galls are highly
conspicuous and tree owners are uncertain of the extent of spread
and the seriousness of the problem.