1994 Forest Health Highlights


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 oak, along with black walnut, have increased by 38 to 54 percent since 1962.

Major Forest Types Special Issues

To date there are no known areas in Illinois where significant tree defoliation has resulted from a gypsy moth infestation. Since the first gypsy moth was discovered in Illinois in 1973, the eradication program conducted by the Illinois Department of Agriculture, USDA APHIS PPQ, and the USDA Forest Service has effectively controlled the gypsy moth in Illinois for over 20 years. A program of trapping (using a chemical attractant of the gypsy moth) and limited use of Bacillus thuringiensis (a biological insecticide) was effective in 1994, and will be used as needed in future years.

Trap counts for the 1994 season were considerably higher than in 1993. A total of 4,672 gypsy moth males were trapped in Illinois in 1994, compared to a total of 1,442 in 1993. Except for a lone moth caught in Union Co., most of the counties where moths were captured were in the Chicago area. Field personnel of the Illinois Department of Agriculture believe that a large number of moths were "blow-ins" from surrounding states. Nearly all the moths were captured in traps within counties bordering Lake Michigan.

Male Gypsy Moth Trap Catches

Male Gypsy Moth Trap Catches Dogwood anthracnose, caused by the fungus Discula destructiva, is a devastating disease of dogwoods that apparently was introduced into the United States 15 to 20 years ago near New York City and Seattle. Dogwood anthracnose was recently reported in Fayette county, but occurs commonly in adjacent states. It's likely that the disease is present in other areas of the state. Dogwoods of all ages are susceptible to the disease. Heavy infection can lead to extensive tree mortality. Once the disease is established, cultural practices and fungicides can be used to manage the disease.

Many areas, especially along the Mississippi River and the southern part of the state, experienced tree mortality associated with the unprecedented flooding of 1993. The tree species most affected were pin oak, shumard oak, cherrybark oak, cottonwood, hackberry and green ash. Overcup oak and bur oak also suffered heavy mortality. Activity of insects and pathogens on trees weakened by the flooding stress may cause mortality levels to remain high for the next several years.

Other Issues

The European Hornet, Vespa crabro, was discovered in 1994 in southern Illinois causing girdling damage to lilac branches. This pest was introduced to the United States in the mid-1800's and occurs in the northeastern U.S., with scattered reports of occurrence throughout the Midwest and in the Southeast. The European hornet is a forest species that feeds on tree bark to acquire sap. They are attracted to light at night, but are not aggressive toward people except in defense of their nest. The wasp often builds its nest in tree cavities and, therefore, could pose a hazard to foresters during tree soundings or harvesting. Presently, the hornet is found in Pope and Massac counties. The importance of this pest in damaging trees remains to be seen.

There has been an increase in mortality of Scotch, Austrian and red pine caused by the pine wood nematode. In addition, there was a high incidence of Sphaeropsis tip blight on Austrian pine and Rhizosphaera needlecast on spruce in the past two years, probably due to high moisture conditions that have allowed the populations to increase. Anthracnose on oak, ash and maple were also high in 1994. Ash yellows, ash decline, Dutch elm disease and oak wilt continue to be present in Illinois and create problems for urban tree managers.

Oak wilt is a serious disease that kills many oak trees annually. A video has been produced which illustrates the range of the disease in the United States, symptoms in oak species within the north-central states, methods of transmission, prevention, and control. The video will be a useful teaching aid and is appropriate for homeowners, arborists, foresters, nurserymen, students, and land managers looking for information and options to manage the disease. The production was made possible through grants and cooperative efforts from the USDA Forest Service, Minnesota Department of Natural Resources, Wisconsin Department of Natural Resources, The Joyce Foundation, Illinois Department of Conservation, and University of Illinois. To order a copy, send a $25 check payable to the University of Illinois to: Agricultural Publications, 67 Mumford Hall, 1301W. Gregory, Urbana, IL 61801, and request oak wilt video OACE#015. Included with the video is a 6 page leaflet published by the Wisconsin Cooperative Extension Service which summarizes the information presented in the video.

Regional Surveys

Counties with Pine Shoot Beetle The Common Pine Shoot Beetle, Tomicus piniperda, was recently introduced to the United States from Europe. To date, the beetle has been found in the following Illinois counties: Cook, DuPage, Iroquois, Kane, Kankakee, Livingston, Will, Kendall, Lake, and McHenry. There is an observed association between where the beetle has been located, dead trees killed by pine wilt, untreated pine stumps, and pine slash piles. Land owners are being advised to remove any pine material that might serve as a site for larval development. To date, the infestations in Illinois have been light.

Butternut in Illinois is being threatened by butternut canker. Scientists are currently collecting plant material from healthy trees that may be resistant to this disease. This plant material will be used in breeding and reintroduction programs.

For More Information

Stewart Pequignot, State Forester
Dept. of Conservation
Div. of Forest Resources
600 No. Grand Ave. West
Springfield, IL 62706

(217) 782 - 2361

Forest Health Protection
USDA Forest Service
1992 Folwell Ave.
St. Paul, MN 55108

(612) 649 - 5261

September 1995

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