BALSAM TWIG APHID ( Mindarus abietinus )
The balsam twig aphid, is an insect that greatly concerns growers of balsam and Fraser fir Christmas trees in New York State. An adult balsam twig aphid is small (1/16-3/16 inch long) and generally pale green. Eggs are the overwinters stage and may be found nestled in bark crevices or scattered on the new shoots of susceptible fir trees.
Eggs hatch in the spring beginning a few weeks before balsam fir budbreak, and the nymphs crawl out onto the previous season's growth to feed on the underside of needles. The aphids feed there until the buds begin to swell and meanwhile cover themselves with a white cottony wax. They begin to reproduce, giving birth to live young, just as the buds begin to swell, and they begin to move onto the buds and crawl beneath the bud scales to feed on the new growth. The most severe damage is caused while the new growth is developing. Aphid feeding causes the needles to bend and curl up around the colony of insects. This damage will not go away even after the insects are gone.
Beginning in mid-April, examine trees which show signs of Balsam twig aphid damage on the previous year's needles. Look for pale greenish aphids feeding alone on the undersides of the needles. If you find a few aphids, wait another week, and look again. The best time to control this pest is when most of the stem mothers have hatched out, but before they begin to reproduce. This means planning to spray (if needed) before budbreak, i.e. during dormancy! Several pesticides are registered for use on balsam twig aphids. If needed, an additional spray may be applied when new growth emerges to control aphids missed by the dormant spray.
Fig. 1. Injury (curling of needles) caused by the feeding of the balsam twig aphid
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