The Norway spruce shoot gall midge is a species of fly that was first discovered in the US in Connecticut in 1983. It is believed to have originated from Europe. The adult midge is tiny - approximately 2 mm long - and upon emerging from the host plant, leaves behind a tiny exit hole. The life cycle and biology of this insect specific to Massachusetts is not yet completely understood. Adults are predicted to be active from late April to mid-May. Eggs are laid between bud scales or near needles of young shoots. Eggs hatch, and larvae feed, creating and living within their galls. Mature larvae may reach 2 mm in length. Larvae may overwinter, and pupation may occur in the spring. Pupation is said to occur within the twigs, with pupal skins sometimes stuck hanging out of the gall following adult emergence. However, again, the exact details of the life cycle of this insect are not yet fully understood. At this time, there may be one generation per year. (Accounts of this insect in its native range note that a single generation occurs per year, with larvae overwintering within the gall. Its distribution is noted to include Europe and Asia, where it is classified as rare (Hartig 1893, Schneider 1962, Huber 1969b).)
There are additional, sometimes native, midge species that this insect may be confused for on different hosts.
This insect has thus far been found to be primarily damaging to landscape ornamentals. Increasingly, reports of sometimes severe damage to its namesake host (Norway spruce) are made on an annual basis. Dieback, thinning foliage, and sometimes bent or distorted twigs are associated with this insect. (Twig terminals may eventually become needle-less.) Larvae create small, almost blistered galls often beneath the prior season's bud scales or near twig tips. Galls may also be found on new growth, twigs, or branches. Needle loss and dieback can sometimes be extensive throughout the host plant. Colorado blue spruce (Picea pungens) has been reported as a potential host for this insect, if growing next to heavily infested Norway spruce. Repeated die-back of the tips of tree branches over several years may cause tree mortality.
Search distorted or twigs with needle loss for blister-like galls. With magnification, galls may be carefully dissected. Galls may be hollow, or contain yellow larvae or pupae (each gall contains a single insect).
Pruning and destroying affected branches prior to adult emergence may help reduce a population of Norway spruce shoot gall midges locally on individual trees.
At least one parasitoid of the Norway spruce shoot gall midge has been reported from its native range, but the status of natural enemies of this insect in the US are not fully understood.
Acephate (NL)
Acetamiprid (L)
Carbaryl (L)
Cyfluthrin (NL)
Deltamethrin (L)
Dinotefuran (NL)
Flonicamid+cyclaniliprole (N)
Gamma-cyhalothrin (L)
Imidacloprid (L)
Lambda-cyhalothrin (L)
Pyrethrins + piperonyl butoxide (L)
Spinosad (NL)
Active ingredients that may be applied systemically include: acephate (injection).
Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.
Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.
