Diseases and Pests in Oak Trees

When it comes to symbolizing strength and stability, there is nothing mightier than the oak. A deep-rooted hardwood, the deciduous oak tree appears to have no enemies...and yet numerous microscopic bugs and diseases can lay an entire oak forest to waste in a short amount of time.

Forest tent caterpillar

A forest tent caterpillar infestation does not always lead to the death of the host tree, but there can be a significant amount of dieback and loss. The caterpillars are easy to identify with pale-blue lines and a brown body adorned with a row of keyhole-shaped spots. Adult moths are brown and possess dark bands. The caterpillars work in clusters along the lower trunks. The moths appear from May through June and lay eggs in winter months. The early signs of an infestation are the sparse crowns at the top of the tree. There are several commercial grade pesticide to control forest tent caterpillars.

Gypsy moth

The gypsy moth is one of the most dangerous pests to red and white oaks in the Northeast. What makes the story even worse is that the caterpillars were imported to the United States to start a silkworm industry. The caterpillar feeds on the foliage of the oak. Egg laid in the fall will hatch and being to feed in spring. Gypsy moths can be controlled by chemical and microbial insecticides.

Oak skeletonizer

The oak skeletonizer has a taste for the red oak tree and attacks the green leaves. The pest eats the green side of the leave leaving only a thin membrane and the veins. From a distance, the leaves take on an almost transparent appearance. Invested trees will have brown leaves and premature defoliations. The best form of control is to rake up the dropped leaves and burn them, thereby destroying the cocoons. Insecticides can be used, but are often difficult to implement.

Anthracnose

Anthracnose is the title for a group of diseases caused by fungi. Oak trees are often targets of the disease with white oak, the most vulnerable. The fungus attacks only a limited number of tree species and will not infect other species. The symptoms vary but generally, the whole leaf dies and falls prematurely. The United States Department of Agriculture (USDA) points out that while most oaks can survive an initial onslaught of the fungus, repeated attacks will weaken the tree until it succumbs. In forest stands, there is little that can be done for control, but individual trees can be sprayed with fungicide and have affected limbs removed.

Oak tatters

Anthracnose is the title for a group of diseases caused by fungi. Oak trees are often targets of the disease with white oak, the most vulnerable. The symptoms vary but generally, the whole leaf dies and falls prematurely. The USDA points out that while most oaks can survive an initial onslaught of the fungus, repeated attacks will weaken the tree until it succumbs. In forest stands, there is little that can be done for control, but individual trees can be sprayed with fungicide and have affected limbs removed.

Oak wilt

Oak wilt is a fungal infection affecting all species of oak. A particularly dangerous disease in red oaks, wilt is almost always lethal. Death can occur in as little as one month and there is no known cure for the affliction. Leaf damage is an early warning of wilt with loss of color and curl being the most noticeable indicators. The Minnesota Department of Natural Resources recommends root graft disruption and tree removal. It is important to remove recently killed trees before April 1st before the spores are consumed by pests and spread.

Keywords: Oak wilt, Oak tatters, Forest tent caterpiller, Scarlet oak sawfly

About this Author

Tom Nari teaches screenwriting and journalism in Southern California. With a degree in creative writing from Loyola University, Nari has worked as a consultant to the motion picture industry as well as several non-profit organizations dedicated to the betterment of children through aquatics. Nari has written extensively for GolfLink, Trails and eHow.