Birch Problems
Birches are extremely susceptible to pests and disease.
Other pests of birch trees are: leaf blister, leaf rust, leaf spot, die back, wood decay, case bearer, birch leaf miner, birch skeletonizer and other fungi and insects.
Birch trees are beautiful and graceful. They are, however, susceptible to several fungus parasites and insect pests. The bronze birch borer is the main killer of birch trees used in ornamental plantings.
Bronze birch borer beetles
The bronze birch borer beetles feed on foliage and deposit their eggs in slits in the bark. They make flat, irregular, winding galleries just beneath the bark of the main trunk. Heavy infestations can kill trees. To control, spray the trunk and branches thoroughly and the leaves lightly with methoxychlor or Lindane as directed by the manufacturer. Spray in early June and twice more at two-week intervals.
Leaf blister…
Leaf blister is caused by fungi. Two types of fungi produce red blisters and curling of leaves on birch trees. Another fungus forms yellow blisters. To control leaf blister, gather and burn all fallen leaves. Spray trees with Ferbam or Maneb just before buds open in the spring.
Leaf rust
Leaf rust causes spotting and defoliation. The rust pustules are bright reddish-yellow. The spores from these pustules carry the infection from leaf to leaf. In ornamental planting, the disease rarely becomes destructive enough to warrant special control measures.
Leaf spot
Leaf spot is the name of several fungi which attack birch trees. They may cause premature defoliation. Control can usually be obtained by gathering and burning fallen leaves. To prevent leaf spot, spray the tree with bordeaux mixture or any other copper spray in the late spring.
Die-back fungus
Die-back fungus attacks trees weakened by drought. It causes a progressive die-back of upper branches. The bronze birch borer causes similar symptoms. Prune the affected branches to sound wood. Fertilize and water the trees heavily to help revitalize them.
A number of wood decay fungi attack birches. Once they become extensive, they can't be controlled. Avoid wounding the trees and maintain good vigor by fertilization.
Birches are also subject to several other fungus diseases such as powdery mildew and leaf spot. Several fungicides are available to help control these fungus diseases.
Aphids
Two aphids affect birch trees: the European birch aphid and the common birch aphid. The European birch aphid is yellow. It infests cut leaved and other birch varieties. The common birch aphid is large and green. It produces honeydew followed by sooty mold. Spray trees thoroughly with Orthene, Diazinon, dimethoate or malathion as soon as these aphids appear.
The case bearer…
A light yellow to green caterpillar with a black head, also attacks birch trees. The pest overwinters, or lives through the winter, as a larva in a case attached to the bark. Spray in late July or early August with a standard malathion solution or spray in late spring, before growth begins, with one part of concentrated lime sulfur in eight parts of water.
The birch leaf miner…
A small white worm, causes leaves to turn brown in late spring or early summer. The adult is a small black sawfly which lives through the winter in the soil. The first brood causes the most damage because it attacks tender spring foliage. Broods hatching during the summer cause less damage because they feed only on leaves on sucker growths, and on newly developing leaves in the crowns of trees.
To control the leaf miner, spray with Diazinon, cygon, malathion or Orthene. For best control, make two additional applications at 1O-day intervals after the first spraying in early sprlng.
Birch skeletonizer
Another insect pest of birch trees. The lower leaf surface is chewed and the leaf is skeletonized and may turn brown. To control the birch skeltonizer, spray the upper and lower sides of the leaves with Orthene about mid-July.
For more information on birch problems; contact your local County Extension Office.
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