The native Betula papyrifera is more resistant to birch borers than other types of birches.
Birch (Betula species) are desirable for their distinctive white or mottled bark and their small, graceful leaves. These moisture-loving trees can often be found growing on the banks of rivers or near other bodies of water. Like all plants, birch trees can suffer from insect problems, and some of the insect pests can be life-threatening. Keeping a birch tree well-watered can strengthen it against insect attacks, according to the University of Saskatchewan Extension Division. Does this Spark an idea?
Deadly Insects
The bronze birch borer (Agrilus anxius) is the deadliest of the insect pests that infest birch trees, according to the University of Wisconsin Extension. These insects commonly attack old or sick trees, which is why proper culture is so important for keeping your birch tree healthy. It is the larvae of this boring insect that causes the most damage. The larvae feed on sapwood, girdling the branches and even the trunks of some trees, and cutting off the flow of nutrients to the rest of the tree. Birch trees usually die from the crown downward.
Disfiguring Insects
The birch leafminer (Fenusa pusilla) can severely disfigure a birch tree due to the large amount of larvae this insect can lay in one growing season. In fact, there are four life cycles of the bug from spring to fall. The adult leafminers lay eggs on the tops of birch leaves. The first set of larvae begins to feed in May. As they eat, black spots appear on the leaves, and they will drop to the ground. Just as new leaves start developing, which happens in many cases, they will be devoured by the second set of larvae, and so the cycle continues, with the birch valiantly trying to put forth leaves and failing each time. Although the tree lives, the canopy will be sparsely populated with brown, spotted leaves.
Minor Insects
Many common insects attack birch trees. Paper wasps peel off the thin, delicate bark of the tree, causing twig dieback to occasionally occur. Aphids and other sucking insects can damage the leaves, but they do not cause life-threatening injuries to the tree, nor are the effects usually very noticeable---although a heavy infestation may cause some of the leaves to drop prematurely from the tree. Look for these and other insects, such as scale, to cluster under the leaves and in the forks of twigs and branches.
Control
While there is no way to cure a tree infested by birch borers or leafminers, if only a small section of the tree appears to be infested, try pruning off the affected branches and then covering the tree with an insecticide. Prevent these and minor insects from gaining a foothold on your birch by keeping it healthy and spraying it with insecticide in the spring and any time insect activity is noticeable.
Prevention/Solution
The best way to prevent insect pests from harming your birch tree is by keeping it as healthy as possible and observing the tree closely for any signs of insects. Proper watering is a must. Birch trees thrive in cool, moist soils but also like a full day's worth of sun exposure. These trees are best grown in climates with cool winters and mild summers and need plenty of room to stretch out their extensive root systems.
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