Illinois Forest Health Highlights, 2002.
The Resource

Illinois forests have many recreation and wildlife benefits. In addition, over 37,000 people are employed in primary and secondary wood processing and manufacturing. The net volume of growing stock has increased by 40 percent since 1962, a reversal of the trend from 1948 to 1962. The volume of elms has continued to decrease due to Dutch elm disease, but red and white oaks, along with black walnut, have increased by 38 to 54 percent since 1962.

Special Issues
Gypsy Moth
Illinois has adopted a program called Slow the Spread. Through this program it is hoped the combined efforts of state and federal agencies will slow the dispersal of this insect into new areas. To date there has been no widespread defoliation of trees in Illinois caused by the gypsy moth.

Asian Longhorned Beetle Through the intensive alb survey efforts of the Illinois Department of Agriculture, USDA APHIS PPQ and the USDA Forest Service the number of infested trees has been dramatically reduced. Only one live beetle was found in the Chicago area in 2003 and only 6 infested trees were discovered.



Pine Shoot Beetle — The first finding of pine shoot beetle in Illinois occurred in 1992 when it was discovered in two northeastern counties. Since then the beetle has spread south and westward. Owners of pine plantations have been informed that the removal of all dead and dying pines, slash, and the treatment of stumps are important practices to lessen the impact of this beetle. Populations of this beetle have remained low and if growers follow the outlined practices this species should remain at low levels.


Japanese Beetle Very heavy infestations were reported in many Illinois counties. The foliage of basswood, oak, crabapple, apple, hawthorn and river birch trees were completely skeletonized by late July. With several years of consecutive severe injury trees become weakened and are often more vulnerable to borer attack.


map -  Foliage of basswood heavily skeletonized by Japanese beetle feeding


map - counties with fall websorm infestationsFall webworm Populations of fall webworm insect vary greatly from year to year. In the northern third of Illinois very high populations occurred on trees such as black cherry, persimmon, hickory, and oak. Some trees were completely defoliated by early August with the trees entirely covered with the webbing.


Bagworm Scattered high populations occurred in the north two-thirds of Illinois. Spruce, white pine, juniper, and arborvitae are common hosts. Complete defoliation of evergreens results in tree death. This insect is more commonly found in urban landscapes although Christmas plantations containing spruce and white pine are vulnerable. Bagworm control is best accomplished with an insecticide application in mid-June after all the overwintering eggs have hatched.


photo - Rows of white pine trees heavily infested with bagwormsmap - Shaded areas indicate counties where high populations were reported


Oak Wilt With the increase in the number of homes being built in oak forests there has been an increase in the number of oak trees infected with oak wilt. During home construction oaks are often pruned or injured. Open wounds then become infected and the fungus spreads throughout the tree resulting in tree death. If oak trees are injured or pruned from March 1 until July 15 in Illinois the wounds should be treated with a tree dressing to prevent infection.

For more information contact:
Mike Mason
Division of Forest Resources
IL Dept. of Natural Resources
524 South Second Street
Lincoln Tower Plaza
Springfield, IL 62701-1787
logo - Illinois DNR Forest Health Protection
Northeastern Area,
State & Private Forestry
USDA Forest Service
1992 Folwell Avenue
St. Paul, MN 55108
Updated: January 2004