Insect and Disease Fact Sheet Compliments of
New Century 
1-877-79TREES
Maple Bladder Gall, Spindle Gall &
Gouty Vein Gall
|
The
upper surface of silver and red maple leaves often become covered with small,
red, round wart-like structures about 1/16 to l/8-inch in diameter. These are
maple bladder galls caused by a small mite. The structures are generally
noticed first in May, about the time the leaves have become fully expanded.
At first the galls are green but they quickly turn pink to red and eventually
black. Leaves frequently become so covered with the galls that they
completely twist out of shape and may even drop early. |
|
On
sugar maple, another leaf gall is commonly found, the maple spindle gall. This
gall is also caused by a mite. The
gall appears as thin, elongate bladders arising from the leaf upper surface.
These galls rarely distort the leaf but considerable numbers of galls can make
the leaves unsightly
The
maple gouty vein gall midge only attacks sugar maple and causes thickened
pouches along the major veins. These galls can completely crumple the early
leaves of maples, often making them look like herbicide damage. The galls are
caused by the larvae of a small gnat-like midge, Felt.
|
Homeowners
often become quite alarmed when they discover that their maple tree leaves
are infested with leaf bladder, spindle or gouty vein galls. They fear that
the tree is going to die unless something is done quickly. This is not the
case. Maple leaf galls seldom, if ever, cause permanent injury to a tree, but
they do detract from the beauty of the leaves. |
|
Damage
Other
than the mere aesthetic damage .and-possible early leaf drop, no significant
damage is done to the health of maple trees. Following a mild winter, damage
from these leaf galls can be excessive but affected trees often send out new
leaves to replace the damaged ones.
Description and Life Cycle
Both
the maple bladder gall and maple spindle gall mites over winter as free living
mites under loosened bark and around the callous growth of wounds, scars and
pruned branches. These over wintered forms produce the gall forming stage in
early spring. When the maple leaves first appear, the mites migrate to
expanding buds and begin to feed on the undersurface of leaf buds. This causes
the formation of a blister which expands into a hollow bladder or spindle as
the leaf expands. The mites enter the cavity and continue to feed within its
protective walls. This stage reproduces asexually within the galls and the new
mites mature by late June to mid-July. At this time the galls dry out and the
tiny entrance hole opens up to allow escape of the
mites. These mites then seek out over wintering sites.
The
maple gouty vein gall midge spends the winter as full grown larvae in the
ground and leaf litter under their
host sugar maples. In late January into early March these larvae spin
small white cocoons in which 1:0 pupate. The pupae rest until April and early
May when the gnat-like adults emerge. These midges have black wings and heads
but the body appears
reddish from the eggs inside. Each female may lay up to 100 eggs among the leaf
hairs on the lower leaf surfaces of expanding leaves. The tiny, maggot-like
larvae hatch in a couple of days and they migrate to the leaf upper surface.
Here they line up in small groups along the major leaf veins. At these congregation
points, the leaves swell and the vein edges fold over to form the galls. Within
a few days the galls are fully formed. The larvae feed within the protection of
the gall until October. At this time the galls dry and a slit-like opening is
formed. The mature larvae drop to the soil to seek shelter.
Control Hints
Since
these leaf galls of maple do not cause any real harm to the trees, control
measures are not generally needed. Tree owners and tree managers are encouraged
to learn about the life cycles of these pests and learn that no lasting damage
will result.
Strategy 1: Use Resistant Maples - Norway maples and some of the named
cultivars of maples with outstanding red or yellow leaf color appear to be
resistant to these gall mites and midges
Strategy 2: Dormant Oils - Some reports of success have
been made where the trunk has been drenched with dormant oil to kill the over wintering
stages of the bladder _all and spindle gall mites.
Strategy 3: Standard Insecticide/Miticide Sprays - Several insecticides and miticides
are registered for control of gall mites (eriophyid
mites) and gall midges. If these-products are to be used they have to be
applied precisely when the new leaf buds are opening. Most sprays have little,
if any, effect because the window of opportunity is very short. Once the gall
has formed, it is too late to make an application.
Strategy 4: Systemic Insecticides/Miticides - Several systemic pesticides (sprayed, soil injected or
trunk injected) have been recommended as useful in controlling these gall
forming pests. However, little evidence of success has been found in the
current literature. Once the gall has formed, it is too late to make an
application.
Information obtained Through the Ohio State University
Extension Factsheet HYG-2004-95
Insect and Disease Fact Sheet Compliments of
New Century
1-877-79TREES