Spruce gall midge
Print
EmailEditor’s note: This article is from the archives of the MSU Crop Advisory Team
Alerts. Check the label of any pesticide referenced to ensure your use is
included.
The
spruce gall midge, Mayetiola piceae, is an unusual pest that we have
found on Black Hills spruce in the northern Lower Peninsula and the
Upper Peninsula. The midge, a tiny fly-like organism, overwinters in
numerous swellings that encircle the terminal shoots. Many of the
swellings have a slight nipple or protrusion (see photo 1) at the end
where the pupa has pushed up against (and occasionally through) the
outer shell; ready to emerge when they complete their development.
The adults which are emerging now in the Lake City area will mate and
lay eggs on the newly developing bud. The bright orange, but tiny,
larvae (see photo 2) hatch within a couple of weeks and bore into the
shoots to feed on plant juices. In response to the feeding, plant tissue
swells up around the larvae to form the galls. The larvae continue to
feed through out the season.
The damage can kill individual shoots (see photo 3). Repeated attacks
can cause brooming, a proliferation of shoots at the ends of the twig
and disfigured growth. (See photo 4)
Fortunately, a tiny parasitic wasp is a common natural enemy and
chemical control is not normally needed. Inspect your trees in the early
spring for signs of the galls. If found, prune those shoots out to
remove the insects before they can emerge. Prune the shoots back to a
side bud or lateral shoot. Be sure to burn or otherwise destroy the
shoots you prune out. If damage is really severe, you miss the time to
prune, and damage is so bad that you feel you must use a chemical
product, treat the newly developing shoots in the next few weeks prior
to egg hatch. Make sure to get good coverage.
