WSU CAHNRS and WSU Extension


Search plant problems by plant name

? Help on search

A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  R  S  T  V  W  Y 

Plant NameTypeDescription 
CankerBirchDiseaseSeveral fungal pathogens can cause canker disease of twigs and branches. Young cankers appear darker and slightly more sunken than adjacent healthy bark. As they grow, they kill living woody tissue, and may cause bark along its edges to crack and fall off. Once a canker girdles a branch or trunk, the portion above the canker dies. Trees with cankers are usually stressed by drought, defoliation, wind damage, nutrient imbalance, flooding, soil disturbance, snow and ice damage, injuries from birds and insects, and other severe conditions. Symptoms may include upper branch dieback, disfigured branches, and target-shaped areas with concentric rings of dead bark on trunks. Cankers generally cause only minor dieback, but may be indicative of poor health.
RustBirchDiseaseBirch rust is a fungal disease which first appears on leaves in early summer. Initially, small yellow angular spots develop on leaves. These may expand into brown spots with yellow edges. Later in the summer, reddish or yellow pustules (powdery-looking clusters) can be found on the underside (and sometimes on the upper surface) of leaves. By late summer, dark brown to black fungal structures may be found as well. Trees may drop infected leaves, sometimes resulting in severe defoliation. This disease can predispose young trees to winter damage or other diseases. Infection is typically worse in cool, wet conditions. The alternate host for birch rust is larch, but larches need not be present for disease development on birches.
AphidsBirchInsectAphids are small yellowish to greenish insects often found on the underside of leaves and on new growth. Aphids on birch typically feed on the leaf veins and produce large amounts of honeydew, a sticky material which may attract ants or become covered with a black growth of sooty mold. Developing leaves which have been injured by aphid feeding may show a typical "corrugated" or wrinkled growth pattern, with the insects often found on the underside in the distortions. Some yellowing of the leaves may be observed with heavy aphid infestations.
Birch leafminerBirchInsectThe birch leafminer is the larvae of a small (about 1/8"-3/8") black sawfly. The adult sawfly lays eggs in new leaves. The larvae emerge and feed in leaf tissues, leaving blotch-shaped or winding brown mines. Mature larvae are flattened and may be up to 1/2" long. Larvae drop to the ground and pupate in the soil for two to three weeks before emerging as adults. There may be up to four generations per year, depending on length of growing season. Vigorous gray, white, and paper birches are most commonly attacked. Repeated severe infestations may result in decline of trees.
Bronze birch borerBirchInsectAdult bronze birch borers are olive to bronze-colored beetles approximately 1/2" long. They lay their eggs in bark cracks or under flaps of bark. The larvae bore into the branches or trunk after hatching and bore winding galleries along the cambial layer (between the wood and the bark). The larvae grow to about 1" long and are creamy to white in color with a head wider than the body. The galleries may heal with swelling showing on the outside of the tree (lumpy bark), or may girdle and kill branches or trunks. Leaves may be yellow (chlorotic) as a result. The adults may feed on leaves, but cause little damage. Bronze birch borers attack trees weakened by age, environmental stresses, or previous insect attacks.
Oystershell scaleBirchInsectOystershell scale insects are found on trunks, branches, and twigs of many broadleaved deciduous plants. They occur less frequently on the leaves and other plant parts. The mature scale is approximately 1/8" long, hard-shelled, brownish or gray in color, and usually elongated like an oyster or mussel shell. Scale infestations are often initially limited to isolated colonies on single branches or twigs. Infested plants may show off-color foliage. Oystershell scales overwinter as eggs beneath the shell of the female scale, then hatch and move to feeding sites in late spring or early summer. Scales are spread from plant to plant by birds, people, wind, or insects.