One generation occurs per year for this species, although adult moths may emerge with staggered timing throughout the summer. It is also suspected that the life cycle of this insect may take 2 years to complete in the colder portions of its range, and perhaps multiple generations are present in warmer locations. When dogwood flowers begin to drop, adult dogwood borer moths begin to emerge. Moth flight and activity can last through September. That being said, it is best to combine phenological indicators, growing degree day tracking, and pheromone trapping to accurately monitor this insect and time treatments. Research has suggested that emergence times for dogwood borer adult moths differ regionally and by host plant. Following mating, female moths lay eggs singly or in small groups, particularly on injured bark. Once hatched from the egg, the larva crawls around the host plant in search of a wound or scar that is sufficient enough to allow its entry. These larvae cannot chew their way into the bark. Limb crotches are also other likely entry points. Larvae feed on phloem and cambium beneath. Larval mines are meandering. Larvae are white in color with a light brown head and just over 1/2 inch in length when mature. Pupae are brown in color and wrapped in a silken cocoon that may be covered in frass (excrement). Pupation may occur in the springtime, just prior to adult emergence. Empty pupal cases may remain stuck to the host plant, halfway protruding from the bark following adult emergence. Adults are agile fliers and active at dawn and dusk.
Bark of trunk and branches. Loose bark may begin to break free of the host plant, sometimes an early warning of dogwood borer infestations. Dieback and adventitious growth are symptoms of longer term infestations. Course brown, sawdust-like frass may be pushed from the galleries created by the feeding larvae. Older trees that have been infested heavily are capable of persisting for years. Infested parts may appear swollen, knotty, calloused, or gall-like.
There are commercially available traps and pheromone lures for dogwood borer to aid in timing treatments to reduce the number of egg-laying adult females. Reports from New York suggest they can be successfully used to time management options, 10 days post trapping the first adult and again as label instructions allow if moths continue to be trapped. Reports from Maryland suggest trapping to time management for this insect has not been so reliable.
Look for brown frass found around wounds and cracks in bark. Removing loose bark may expose larvae beneath in tunnels under the bark, near these wounds. Dead branches and adventitious growth can be additional signs of the presence of dogwood borer on its hosts.
This clearwing moth requires a wound to enter the host plant so avoid wounding plant with mowers, etc.; mulch around tree base for protection. Painting fresh bark wounds on host plants of the dogwood borer with white latex paint has been suggested to protect against infestation. Avoid making pruning cuts on host plants during the time of the year that adult moths are actively flying. Maintain host plant health and vigor. Kousa dogwood appears (by most accounts) to be resistant to this insect, so consider installing Cornus kousa instead of Cornus florida, particularly in landscapes where this insect is a frequent pest. Tree wraps have been suggested to protect young trees from dogwood borer infestation, but have variable results. In some cases the use of vinyl tree wraps around the trunk of young dogwood trees reportedly increased dogwood borer infestation (Owen 1991).
Entomopathogenic nematodes have shown very good results. Be sure to purchase a species that the manufacturer lists as being effective at managing dogwood borers. Remember: entomopathogenic nematodes are living organisms, and require special storage and care when using. "Watering in" the nematodes can also help increase effectiveness. No effective natural parasites or predators are known, however woodpeckers and other birds, bats, and spiders have all been listed as potential predators of the dogwood borer.
Abamectin (NL)
Acephate (NL)
Azadirachtin (NL)
Bifenthrin (NL)
Chlorantraniliprole (NL)
Chlorpyrifos (N)
Cyantraniliprole (NL)
Emamectin benzoate (L)
Entomopathogenic nematodes (L)
Permethrin (L)
Contact insecticide sprays should target the adult stage, thoroughly coating the trunk and lower branches when making applications. Entomopathogenic nematodes can be used to target the larvae, which are otherwise protected beneath the bark from contact insecticides.
Active ingredients that may be applied systemically include: abamectin (injection), acephate (injection), azadirachtin (injection, soil drench), cyantraniliprole (soil drench, soil injection), and emamectin benzoate (injection).
When used in nurseries, chlorpyrifos is for quarantine use only.
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.
