Johnson’s Flower and Garden Center

Pest Bulletin #3

DOGWOOD BORER

(Synanthedon scitula)

 

How to Identify Damage

Dogwoods attacked by borers will have branches lacking flower buds, leaves, and overall foliage density. Plant crown dieback is typical on severely affected trees. Sloughing of bark, frequently with a sawdust-like material mixed in, indicates that borers are present. New branch (supple) shoots immediately below the damaged area may also indicate that borers have infected the tree.

 

Life Cycle

Dogwood larvae over winter inside the host frees just under the bark. They pupate and emerge as adults around the time when the dogwood plant drops its last petals, about late April. The adults mate, and the female shortly begins laying eggs on a prospective host. Since newly hatched larvae do not have mouth parts capable of piercing bark, the eggs are laid where there is ready access to the inner parts of the free, for instance, wounds, scars, or previously attacked areas. Once inside the free, the larvae tunnel in a random fashion, feeding on phloem and cambium, destroying the tree’s ability to transport nutrients and water as well as its ability to grow. There is only one generation per year, and these larvae survive within the tree during the winter.

 

Critical Control Time

Since it is difficult to reach the borers once they are within the tree, the best time to effect control is during the crucial period between when the eggs are laid and when they hatch and penetrate the bark. Two applications of a pesticide during mid-April to mid-May should protect the plant. Concentrate your application on those areas with wounds or broken bark.

 

Control Strategies

Torn, broken, and wounded trunks and branches invite borers to attack your dogwood. Avoid damaging your plant by inadvertently hitting the base with a lawnmower or other object. Avoid actions that could damage the bark. Fertilize and water the plant to keep it as healthy and vigorous as possible and to speed the healing of wounds.

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