Order:    Diptera

Family:    Cecidomyiidae

Latin Name:    Paradiplosis tumifex Gagneé

Common Names:    Balsam Gall Midge

Introduction
Top

As their name suggests, balsam gall midges are tiny flies that cause swellings on balsam fir needles. If numbers are high, large numbers of needles can be infested and eventually drop, making the tree unsuitable for the Christmas tree market.

Life History
Top

The adult gall midge is a small delicate orange-coloured fly. The adults emerge from pupae in early spring. Eggs are deposited between the needles of partially opened buds. The larvae travel to the base of the needles and through chemical or mechanical means cause the needle to envelop them and form the gall. The larvae feed within this gall during the summer and as autumn approaches, drop from the galls and crawl into the soil. The infected needles die and eventually drop to the ground. The insect overwinters as a larva within a silken cocoon and pupates in the spring.

Damage Symptoms
Top

The gall of the balsam gall midge is the only damage attributed to this pest. In severe infestations, heavy defoliation may occur resulting in unsightly Christmas trees and a possible reduction in growth. This insect rarely causes permanent damage and if infested Christmas trees are not to be harvested for another 3-4 years, they may outgrow the damage.

Control Options
Top

Control is often very difficult due to the short period that the larvae are exposed. Once the larvae are enveloped by the needle within the gall, it is futile to spray for it.

The recommended time for an insecticide application is when the buds are at least 20% flushed. This will kill most of the larvae before the gall forms.

The key control agent is a predator midge which will normally causes a population collapse for the balsam gall midge.