Balsam Twig Aphid
Order: Homoptera
Family: Aphididae
Mindarus abietinus
Overview
Balsam fir (Abies balsamea) is a commonly grown Christmas and ornamental tree species in New England and serves as the primary host to the balsam twig aphid. In the spring, the piercing-sucking feeding activity of this pest causes the newly emerging needles to become twisted and the copious amount of honeydew produced causes the new shoots to stick together. Injury from this pest will persist on the tree in the current and sometimes the next growing season, and heavy attack during harvest years can render Christmas trees unfit for sale, despite the injury being only aesthetic. (Some have reported injury persisting on trees for 2-3 years.)
Host Plants
The preferred hosts of the balsam twig aphid are fir (Abies spp.) species including alpine fir (A. lasiocarpha), balsam fir (A. balsamea), Fraser fir (A. fraseri), grand fir (A. grandis), Siberian fir (A. sibirica), and white fir (A. concolor). Other host species include Colorado spruce (Picea pungens), juniper (Juniperus spp.), and white spruce (Picea glauca). These other hosts may be more likely to have issues with this species of aphid if heavily infested, preferred host species are growing nearby.
Identification/Life Cycle
Eggs overwinter in the cracks and crevices of host plant bark on the trunk and branches. Eggs are dark brown to black in color and covered in white waxy rod-like structures. Eggs hatch approximately in April and May and become nymphs that mature quickly into "stem mothers" which are wingless and can each produce 20-40 living young without laying eggs. These new young feed on buds and tender needles, making them an early-season pest and causing the most damage at that time. This generation will mature into a winged adult form capable of dispersing to other trees and mating. These aphids can feed, but in this later stage they are much less damaging to the plants than those born of the stem mothers. This generation will lay brown eggs and cover them with white, waxy material onto the bark cracks and crevices which will overwinter for the next season. The aphids themselves are yellowish-green, ranging from 1.5-3.0 mm (0.05 in to 0.11 inch) in length. The bodies of all life stages of this species of aphid have a dense, waxy covering. Wax is freshly secreted after each molt, so freshly molted instars have little to no wax, while adults are covered in long tendrils. This wax may obscure the color of the aphids themselves. It is thought that this wax prevents the aphids from becoming encased in their own sticky honeydew. It may also serve to protect the aphids from fungi, parasites, predators, as well as aid in their own microclimate comforts such as waterproofing and frost protection. Several generations can occur per year. All feeding from the balsam twig aphid typically ceases by early to mid-June in southern New England.
Damage
Damage by the balsam twig aphid is usually not noticed until the pest has gone. This is a very early season pest and damage may stay on the host into the next growing season. The balsam twig aphid creates much honeydew (sticky, sugary liquid waste) and distorts foliage (twists needles around itself) as it feeds. Honeydew can stick needles together in heavy populations. Some needle death may occur. Pest active at bud break. This insect may be a significant aesthetic issue in Christmas trees, impacting their sale. In some cases, the growth of small trees may be stunted.
Management Strategies:
Monitoring for the balsam twig aphid includes looking for the curled or stunted needles from previous season's damage from roughly July through March. If damage is noted, scan bark for white-covered eggs. When monitoring aphid activity in the early spring (April), scout trees likely to break bud the soonest, as those may become infested first. Research done in Michigan showed that egg hatch began at approximately 60-70 GDD’s (base 50F) and continued through approx. 100 GDD’s. Newly hatched aphids are tiny and difficult to see without magnification. By mid-to-late April in Michigan (approx. 100-140 GDD’s, base 50F), first generation stem mothers are large enough to see against a dark background (Michigan State University Extension Bulletin E-2813, 2002).
Once population sizes of economic importance have been established, it is then necessary to apply effective management measures. Historically, management of this insect has been difficult. Horticultural oils or insecticidal soaps may be ineffective if the needles are twisted around the aphids, preventing contact.
Cultural/Mechanical Management:
Avoiding the application of nitrogen fertilizers to infested trees is one way to reduce the risk of possibly increasing balsam twig aphid numbers. Nitrogen fertilizers have been shown to benefit certain aphid species and other piercing-sucking feeding insect pests.
There is hope that host plant resistance may someday be a beneficial way of managing balsam twig aphids. Hosts that break bud the earliest are most often the ones to be severely attacked. For example, many types of balsam fir break bud before Fraser fir trees, even those growing at the same site. The timing of bud break also varies between individuals within the same species. Identification of varieties or individual trees that break bud later in the season and selective propagation of those trees may aid in balsam tree aphid management in the future (Michigan State University Extension Bulletin E-2813, 2002).
Biological Control/Natural Enemies:
Choose chemical management options (if necessary) that are least detrimental to beneficial insects that act as natural enemies. Many insects will prey on balsam twig aphids, including but not limited to adult and larval lady beetles (Harmonia axyridis and Anatis mali), lacewings, and the larvae of syrphid/flower/hover flies. Insect predators of balsam twig aphids can be a significant factor in reducing their populations and maintaining low, non-damaging aphid numbers.
Augmentative biological control can include the purchase of commercially available green lacewing larvae, which can be released on individual trees to reduce the number of feeding aphids. One lacewing larva may be able to consume up to 35 aphids per day. Releases of approximately 1 tablespoon of lacewing larvae onto each tree in mid-May significantly decreased the amount of aphid damage that occurred in trials in Michigan (Michigan State University Extension Bulletin E-2813, 2002). Reach out to lacewing distributors for availability, instructions for use and costs.
Chemical Management:
There are products available containing the following active ingredients labeled for use against balsam twig aphid in Massachusetts: abamectin (NL), acephate (NL), acetamiprid (L), azadirachtin (eggs) (NL), Beauveria bassiana (NL), bifenthrin (NL), carbaryl (L), chlorantraniliprole (NL), chlorpyrifos (N), Chromobacterium subtsugae (NL), clothianidin (NL), cyantraniliprole (NL), cyfluthrin (NL), cypermethrin (NL), dinotefuran (NL), emamectin benzoate (L), fenpropathrin (NL), flonicamid+cyclaniliprole (N), gamma-cyhalothrin (L), horticultural oil (L), imidacloprid (L), insecticidal soap (NL), Isaria (paecilomyces) fumosoroseus (NL), lambda-cyhalothrin (L), malathion (L), neem oil (NL), permethrin (L), pyrethrins+piperonyl butoxide (L), pyrethrin+sulfur (NL), pymetrozine (NL), pyriproxyfen (eggs and immatures) (L), spinetoram+sulfoxaflor (N) and tau-Fluvalinate (NL).
Spray on warm days. Oil or soap sprays may not reach all aphids hidden in curled needles.
Active ingredients that may be applied systemically include: abamectin (injection), acephate (injection), acetamiprid (injection), azadirachtin (injection, soil drench), chlorantraniliprole (soil drench), clothianidin (soil drench), cyantraniliprole (soil drench, soil injection), dinotefuran (soil drench), emamectin benzoate (injection), imidacloprid (soil drench), and neem oil (soil drench).
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.
Read and follow all label instructions for safety and proper use. If this information contradicts language on the label, follow the most up-to-date instructions on the product label. Always confirm that the site you wish to treat and the pest you wish to manage are on the label before using any pesticide. Active ingredients labeled "L" indicate some products containing the active ingredient are labeled for landscape uses on trees or shrubs. Active ingredients labeled "N" indicate some products containing the active ingredient are labeled for use in nurseries. Always confirm allowable uses on product labels. This active ingredient list is based on what was registered for use in Massachusetts at the time of publication. This information changes rapidly and may not be up to date. If you are viewing this information from another state, check with your local Extension Service and State Pesticide Program for local uses and regulations. Active ingredient lists were last updated: September 27, 2024. To check current product registrations in Massachusetts, please visit the MA Department of Agricultural Resources Pesticide Product Registration page and click on "Search Pesticide Products Registered in Massachusetts - Kelly Solutions".
References
Aphids - Mindarus abietinus
Michigan State University Extension Bulletin E-2813: Biology and Management of Balsam Twig Aphid (2002)
NC State Extension Balsam Twig Aphid Fact Sheet
UMass Extension Insect Management Guide
Authors
Updated by Tawny Simisky and Paige Brown.