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.

Illinois Major Forest Types.
Special Issues
Eastern tent caterpillar — Moderate to heavy defoliation of black cherry trees occurred during April and May especially in the counties of the southern third of the state. Crabapple and apple trees were also attacked. Black cherry trees readily refoliate after complete defoliation but growth is retarded.
Small black cherry tree completely defoliated . Eastern tent caterpillar Infestation - map.

Bagworm —
In some central and southern counties moderate to heavy infestations occurred. 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. Control is best accomplished with an insecticide application in mid June after all the overwintering eggs have hatched..

Large white pine trees died after being completely defoliated by bagworms. Bagworm infestations in 2002 - map.

Leaf Tatters — White oak species and hackberry have developed a leaf condition in the spring months called leaf tatters. For approximately the last 13 years trees in Illinois have been affected. In severe conditions there is no development of leaf tissues between the major leaf veins. The first spring flush of leaves is affected, but the second spring flush develops normally. The cause remains unknown but herbicide drift from agricultural fields is suspect. Trees severely affected may be weakened. It is advisable to water affected trees during drought conditions to lessen stress. In 2002 leaf tatters were reported only in the northern half of Illinois. The cool very wet spring in the southern half of the state greatly delayed spring planting and as a result leaf development was advanced before field herbicides were applied.


White oak foliage showing severe symptoms of leaf tatters. White oak foliage showing severe symptoms of leaf tatters - map.

Periodical Cicada — Adult emergence of cicadas were heavy in scattered areas of southern Illinois. Female cicadas damage the outer branches of many trees when they insert their eggs into the twigs. Many of the affected twigs die. Apple and peach yields are often reduced because of the death of the fruit bearing branches.

Forest tent catapillar defoliation.Forest Tent Caterpillar — A very high population occurred in extreme southwestern Illinois in Jackson County in the Oakwood Bottoms Recreational Area where about two thousand acres were defoliated in May. This mixed forest is mostly pin oak, elm, and hackberry. The area is purposely flooded in the fall months to attract waterfowl. Defoliation greatly lessens the amount of oak mast, which reduces the attractiveness of the area to ducks. All larvae observed in late May showed symptoms of a viral infection. The population in 2003 should be low.

Asian longhorned beetle on silver maple trunkAsian Longhorned Beetle — The number of beetle infested trees has been greatly reduced in Illinois. The fine cooperative efforts and programs of the Illinois Department of Agriculture, APHIS PPQ, USDA Forest Service, Chicago Municipal Departments, and the Chicago newspapers and television stations have paid off. The continuation of tree surveys and treatments of healthy trees near the previously infested areas is very important if this beetle is to be contained.
Breaks in the bark cankers and a resulting resin flow down the stem .White Pine Decline — The symptoms are a lack of tree vigor with shortened spring growth. Affected trees often live several years before dying. In some areas of the trunk bark a slight bungle may develop and then a crack from which resin flows. If the bark is removed from such an area a brown stain is found on the xylem tissues. To date laboratory analysis has not revealed the cause.
Xylem resin stain.Xylem resin stain.

Gypsy Moth — Illinois has adopted a program called Slow the Spread. Through the combined efforts of state and federal agencies it is hoped that the program will slow the dispersal of the insect into new areas. Through treatments and continued trapping to locate any new infestations outside the containment areas it is hoped that the establishment of the moth into new areas will be slowed.

Gypsy moth caterpillar. Gypsy moth trap catches 2001 - map.
Damage to black locust .Locust leafminerModerate to heavy infestations occurred in southern Illinois in the Shawnee National Forest. The injury became noticeable in mid July. By mid September many black locust trees were near complete defoliation.


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
Illinois DNR Logo. Forest Health Protection
Northeastern Area,
State & Private Forestry
USDA Forest Service
1992 Folwell Avenue
St. Paul, MN 55108
Northeastern Area Logo.
Updated: March 2003