No. 6/August 15, 2023

Fall Webworm
Fall webworms (Hyphantria cunea) are communal caterpillars that spin silk into a tent-like structure at the tip of branches. These webs are often built around the leaves they feed on. Fall webworms feeds on a wide range of deciduous trees and shrubs including, crabapple, redbud, sweet gum, maple and oak. As the caterpillars consume the leaves within the web, they will expand the web every week or so to include more leaves. The web of mature caterpillars can be 2 to 3 feet long.

Tree-of-heaven (Ailanthus altissima) has gained some attention with the pending threat of invasive Spotted Lanternfly (SLF) making its way to Illinois. Currently, populations have been identified in neighboring states, so it really is just a matter of time before it settles in Illinois. Tree-of-heaven is the preferred host species for SLF. Controlling tree-of-heaven is important in keeping SLF at bay.

Oak Wilt
Oak wilt is a serious fungal disease that continues to kill oak trees in residential areas, parks, farm woodlots, and forests throughout Illinois. The disease was first detected in Wisconsin in 1944 and has slowly spread throughout the central and eastern United States. I recently had an opportunity to attend an oak wilt management workshop hosted by US Forest Service. The workshop was geared towards managing the disease in woodlots and forested areas, but many of the disease management principles and goals also apply to landscapes. Though, land managers in forested areas often contend with site accessibility and difficult terrain.

Bacterial Leaf Scorch of Shade Trees
Bacterial leaf scorch (BLS) symptoms are evident on many oaks in central Illinois. This disease causes a slow, multiyear decline and eventually death of the host tree. BLS is caused by the bacterium Xylella fastidiosa, which is also responsible for Pierce’s Disease in grapes and is currently causing widespread damage to the Italian olive industry.