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Douglas-Fir Needle Midges
Contarinia pseudotsugae, C. constricia, and C. cuniculator
Condr.
From: Field Guide to Diseases and Insect Pests of Idaho and Montana Forests, USDA Forest Service Northern Region, Publication Number R1-89-54
Hosts. – Douglas-fir.
Distribution. – Throughout host range.
Damage. – Maggots (larvae) cause galls on current needles
and can destroy most of the foliage if severely infected (fig.
109). Economic damage occurs in Christmas tree plantations. Needles fall off
and, after consecutive years of defoliation, twig dieback can occur.
Identification. – Noticeable galls may be
seen on new needles starting in June (fig. 110). Galls of C pseudotsugae are
swollen on the lower surface and colored on both surfaces with yellow, pink, or
purple. C. constricts galls first appear as a patch of yellow discoloration with
a dark purplish spot visible on both surfaces of the needle. After about 6 weeks
the gall becomes dilated and flattened. C. cuniculator galls affect mainly the
upper needle surface. The upper side is dirty yellow with a glossy, waxy
appearance. Frequently needles are bent at site of injury. See Table 4 for
comparison of needle midge damage with needle casts and adelgids.
There is one generation of these pests each year.
Winter is passed as larvae in the soil. Adults appear in early May but are
seldom noticed as they are small midges not much more than three-sixteenths inch
long. |
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Figure 109. – From a distance, the damage
on this Douglas-fir resembles that caused by
needle cast, needle midge, and Cooley spruce
gall adelgid. In this case, the damage was
cause by Douglas-Fir Needle Midge. |
Image Unavailable
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Figure 110. – Needle infested with Douglas-
Fir Needle Midge have swellings or galls which
are discolored yellow or red. The tiny larva
can be seen in the opened gall on the left. |
Similar damages. – Look for needle 'galls"
to identify. Rhabdocline needle cast, Swiss needle cast, Cooley spruce gall
adelgid and, occasionally, aphids cause similar types of damage to Douglas-fir
needles, but none of these produce galls.
Link to Table 4. – Comparison of Needle Problems of Douglas-Fir.
Link to Images in Forestry Images
References. 2, 15
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