Recognize and manage balsam twig aphid

Time to scout if you had Fraser or balsam fir trees damaged last year

Balsam twig aphid egg begin to hatch early in spring, at roughly 60 to 70 degree-days base 50°F (DD50) and continued until approximately 100 DD50. The newly hatched aphids are very small and difficult to see, at approximately 100 to 140 DD50, they have grown enough to be easily visible against a dark background. These first-generation aphids are called “stem mothers.”

Target the stem mBalsam twig aphids on balsam fir.others

When spraying is necessary, it is critical to apply insecticides at the proper time to prevent damage to current-year foliage. The ideal time to spray is at 100 to 140 DD50, after the stem mothers have hatched, but before the sexuparae, or second generation, aphids are present. Typically at this point, buds are swelling, but have not yet broken, and the stem mothers have hatched and are exposed at the ends of the shoots. It is very important to control the stem mothers before they produce the sexuparae. The sexuparae typically feed inside the expanding bud and are well protected from insecticides.

Balsam twig aphids on balsam fir.

If you had Fraser or balsam fir trees that were heavily damaged by this aphid last year, you will probably want to begin scouting now and into next week. Scout the trees that were damaged last year as that's where you will be most likely to find aphids this year. If you had heavy damage last summer and you are planning to harvest trees this year, you can apply an insecticide this spring. To prevent damage to your tree, you will need to kill the stem mother – this first generation.

Shoot on left heavily damaged from feeding by balsam twig aphid, with a normal shoot on right.
Shoot on left heavily damaged from feeding by balsam twig aphid, with a normal shoot on right.

Keep in mind, however, that if aphid populations are not very high and you did not have heavy damage last year, you may not need to spray. There are many different kinds of predators that will be happy to feed on your aphids, all summer long.

For more information, read MSU Extension bulletin E-2813, Biology and Management of Balsam Twig Aphid.

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