It's ironic that the same thing that makes white birch trees so beautiful also makes them more susceptible to pests because their uncommon white bark is not as thick or tough as the barks of other trees. Identifying which pests are most damaging to white birch trees is the first step in prevention.
Bronze Birch Borer
The bronze birch borer (Agrilus anxius) is a serious threat to birch trees in the Midwest, and white birch trees are the most susceptible, according to University of Wisconsin associates R.C. Williamson and P.J. Pellitteri. The first sign of an infestation is thinning or dying back of branches on the upper third of the tree. Eventually, ridges may appear on the bark as larvae feed on the wood. Borers manage to kill many birch trees because they target trees that are already weakened. The best method of controlling borers is to keep your birch trees healthy by planting them in full sun in cool, moist soil. Also, provide your birch trees with adequate water, especially during times of drought.
Birch Leaf Minor
Birch leaf minors (Fenusa pusilla) are the larvae of small sawflies which feed on the leaves of many birch trees. The first signs of an infestation are small, translucent blisters on new leaves. The leaves will eventually turn brown and fall off. Light infestations are usually not a problem, provided they don't affect more than 30 percent of the leaves. But any infestations weaken birch trees and make them less able to deal with other stresses, such as drought or excessive heat. Birch leaf minors also weaken the tree's resistance to bronze birch borers, according to University of Wisconsin Insect Diagnosis Laboratory specialist Phil Pellitteri. Although the leaf minors have several natural enemies, they are not plentiful enough in Wisconsin to be a solution. Chemical control is the only effective method.
Gypsy moth caterpillars are becoming an increasing problem of forest and shade trees in eastern Wisconsin, state R. Chris Williamson and Andrea Diss in their article "Identifying and Managing Gypsy Moth Caterpillars." Signs that a tree is infested begins in May with pin-sized holes on the leaves. Eventually, by mid-June, the caterpillars grow large enough that they can be seen on the trees. Gypsy moth caterpillars are hairy with five pairs of blue warts followed by six pairs of red warts visible on their bodies.