No. 14/August 17, 2015
Reminder: Test NOW for Bacterial Leaf Scorch
As a reminder, the University of Illinois Plant Clinic is testing for Bacterial Leaf Scorch (BLS). This serious disease affects a wide range of woody ornamentals, causing leaf discoloration and margin necrosis. BLS can often be confused with environmental scorch, Oak Wilt (in oaks) and occasionally with Verticillium Wilt in other woody ornamentals. The Plant Clinic tests symptomatic leaves once a year, at the end of the growing season when the bacterial populations are highest.
Tar Spots of Maple
Tar spot has been evident on many species of maple this year. Tar spots of maple are caused by several different fungi in the same genus, Rhytisma americanum, R. punctatum, and R. acerinum. Each is known to cause raised, black spots on upper leaf surfaces. Affected leaves appear as if splattered with tar, hence the name Tar Spot.
With all the rain, powdery mildew hasn't been as much of a problem, though it has shown up on a few of the garden flowers. Powdery mildew really prefers the hot humid days where rain fall is practically non-existent. Probably because many of the flowers have grown tall and leggy, mildew has been kept in check by air movement; when foliage is dense, mildew is more of a problem.
Emerald Ash Borer
Due to uncertainty about last week's report of emerald ash borer being found in white fringetree at the Morton Arboretum, the Illinois Department of Agriculture needs additional information about its status as an Illinois host.
Zimmerman Pine Moth
Zimmerman pine moth is a common trunk and scaffold branch borer in Scotch, Austrian, and red pine in Illinois. It is a shoot tip borer in Eastern white pine. Although it is difficult to control once inside the tree, its life cycle makes it relatively easy to control while on the outside of the tree.