What are Those Tiny Bugs on Balsam Firs? A Close Look at Balsam Twig Aphids

As a balsam fir owner, you may have noticed some tiny insects congregating on the stems and needles of your tree. These small, sap-sucking bugs are known as balsam twig aphids, and they can be a common pest on balsam firs. In this article, we’ll take a close look at balsam twig aphids – what they are, what they look like, and how to control them if they become a problem.

What are Balsam Twig Aphids?

Balsam twig aphids, as their name suggests, are a species of aphid that feeds on balsam fir trees. Their scientific name is Mindarus abietinus. They have a complex lifecycle that involves multiple generations per year and both sexual and asexual reproduction. The aphids overwinter as eggs on fir trees, usually in bark crevices, terminal buds, or needles. The eggs hatch in spring when fir buds open.

The tiny nymphs that emerge feed on the youngest growth of the tree There can be several generations of aphids throughout spring and summer. The aphids reproduce asexually during this time, giving birth to live young. In fall, they produce a generation of winged aphids that migrate to spruce trees, where they mate and lay overwintering eggs The eggs then hatch the following spring, beginning the cycle again on balsam fir.

Identifying Balsam Twig Aphids

Balsam twig aphids are very small measuring only about 2 mm in length. Despite their tiny size, colonies of hundreds of aphids can build up rapidly, making them more noticeable.

Some key identifying features of balsam twig aphids include:

• Color Can range from pale yellowish-green to bluish-gray Often covered in a white “woolly” wax secretion,

• Body shape: Oval and somewhat pear-shaped. The rear of their body may appear swollen.

• Cornicles: Small tube-like structures protruding from the rear end. These structures secrete pheromones and defend against predators.

• Antennae: Short antennae with 6 segments.

• Legs: 6 legs, may appear thick and stubby.

• Feeding: Feed by sucking sap from tender shoot growth. Colonize at bases of needles and bark crevices.

If you spot a cluster of tiny (1-2 mm), grayish, oval insects on your balsam fir’s stems or needles, there’s a good chance they are balsam twig aphids. Their waxy, cottony secretions are another giveaway.

The Lifecycle and Habits of Balsam Twig Aphids

To understand balsam twig aphids, it helps to learn about their rather complex lifecycle:

• Spring: Overwintered eggs from last year’s generation hatch as fir buds open in spring.

• Early Summer: The nymphs feed on fresh fir growth and progress through multiple generations. Reproduction is asexual during this time.

• Mid-Summer: Winged aphids develop and migrate from fir to spruce trees.

• Late Summer: Sexual reproduction occurs on spruce, resulting in eggs being laid in bark crevices.

• Fall & Winter: Eggs overwinter on spruce. The cycle repeats next spring when eggs hatch and aphids return to balsam fir.

During summer, the aphids tend to feed on the tender, younger parts of the tree – usually the current year’s shoot growth. They prefer to feed at the bases of needles and in protected areas like bark crevices. Their saliva is toxic to plants and can cause yellowing, distortion, and stunting of the shoots. Honeydew secretions also promote the growth of sooty mold fungus.

Signs of Balsam Twig Aphid Infestation

A minor aphid infestation may go unnoticed. But heavier infestations can lead to:

• Stunted, distorted shoot growth
• Yellow or reddish discoloration of needles
• White wax or cottony secretions on stems and needles
• Honeydew drippings and sooty mold growth
• Branch dieback in severe cases

Check for aphids on new shoot growth, as well as honeydew and cottony material on needles. Look closely, as the aphids themselves are tiny. Ants may also be present feeding on the honeydew.

Controlling Balsam Twig Aphids

Light aphid infestations often do not require control. Natural predators like ladybugs and lacewings will help keep populations in check. But if shoot growth becomes heavily infested, controls may be needed to prevent damage. Options include:

• Insecticidal oils and soaps: These smother and kill aphids on contact, but require good coverage. Target nymphs early before populations build.

• Horticultural oil sprays: Use a dormant oil spray in late winter/early spring to kill overwintering eggs. Summer oils can also smother aphids. Avoid spraying opened buds.

• Insecticides: Systemic insecticides that are taken up by the tree provide longer control. Apply early as a drench for best results. Use as directed.

• Pruning: Prune out heavily infested branches to quickly reduce populations. Destroy the pruned material.

• Plants health: Avoid excess nitrogen fertilization, prune for airflow, and keep trees healthy to withstand aphid damage better.

With diligent monitoring and timely control when needed, balsam twig aphid damage can be minimized. But don’t worry about a few aphids here and there – as they rarely cause significant harm to established, healthy balsam fir trees. They’re just part of the complex web of insects found in the landscape.

A Few Frequently Asked Questions

Q: Will balsam twig aphids kill my fir tree?

A: In most cases, no. Some shoot dieback may occur in severe infestations. But they rarely kill established trees outright. The biggest risk is to young transplants if populations explode. Monitor yearly and control excessive numbers.

Q: Should I spray my tree preventatively for aphids?

A: Preventive spraying is not necessary in most cases. Try to preserve beneficial insects by only spraying if significant infestations occur. Monitor in early summer and target young nymphs.

Q: Are balsam twig aphids the same as woolly adelgids?

A: No, balsam woolly adelgid is a different type of aphid-like pest that feeds on bark. Balsam twig aphids target shoot growth rather than bark. But both secrete woolly wax.

Q: Do balsam twig aphids harm spruce trees?

A: No, the winged migrants that spend fall on spruce do not feed significantly on them. Spruce acts more as an overwintering host. The main damage occurs during summer on balsam fir.

Q: Should I prune off all infested branches?

A: Selective pruning of highly infested stems can help reduce high populations. But avoid excessive pruning that stresses the tree. Enough foliage needs to remain for plant health.