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The Douglas-fir gall midge, Contarinia pseudotsugae, is a small fly in
the family Cecidomyiidae. It is native to western North America, where
it feeds on Douglas-fir trees (Pseudotsuga menziesii). The larvae of the
midge form galls on the needles of the tree, causing them to become
swollen and distorted.
The adult midge is a small, delicate fly,
about 2 mm in length. It has a dark brown or black body and long,
slender legs. The wings are clear, with a few dark spots. The larvae are
small, white maggots, about 1 mm in length. They have a long, pointed
head and a segmented body.
The Douglas-fir gall midge overwinters
as a larva in the galls. In the spring, the larvae emerge from the galls
and pupate in the soil. The adults emerge from the pupae in the summer
and lay their eggs on the needles of Douglas-fir trees. The larvae hatch
from the eggs and feed on the needles, causing them to form galls.
The Douglas-fir gall midge can cause significant damage to
Douglas-fir trees. The galls can reduce the tree's ability to
photosynthesize, which can lead to reduced growth and vigor. In severe
cases, the tree may die.
There are a number of ways to control
the Douglas-fir gall midge. One method is to apply insecticides to the
trees. Another method is to prune the infected needles from the tree.
Biological control is also a possibility. There are a number of natural
enemies of the Douglas-fir gall midge, including parasitic wasps and
predatory beetles.
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