No. 15/September 11, 2017

Whiteflies are being found commonly in the landscape, feeding on the leaves of flowers and other herbaceous plants as well as shrubs and trees. Generally, late season whiteflies can be ignored, as they are too late to cause serious damage to plant health or even cause obvious aesthetic damage. They are 1/16-inch-long insects with white, powdery wings. They sit on leaf undersides and fly off infested foliage when disturbed, frequently being numerous enough at this time of year to be obvious. They are sucking insects, whose removal of sap can cause leaf distortion.

Stinging Caterpillars
Almost all caterpillars are harmless when handled, their impact to us is primarily from their feeding on plants. A few caterpillars possess stinging hairs and barbs that cause various reactions from itchy rashes to painful stings. They are easily recognized by their physical appearance, being colorful with obvious hairs and spines. These include the Io, imperial, and saddleback caterpillars.

Tar Spots of Maple
Tar spots have been evident on many species of maple this year. Several different fungi in the genus Rhytisma cause this disease. Tar spots result in raised, black spots to on upper leaf surfaces. The symptoms are distinct, allowing for and easy diagnosis. Affected leaves appear as if they splattered with tar, hence the name Tar Spot.

Bur Oak Blight Moves South in Illinois
Bur Oak Blight (BOB) is a potentially serious fungal disease that only affects bur oak trees. After first being reported in Illinois in 2012, the Plant Clinic has received symptomatic samples almost every year. The pathogen was first identified in Iowa and appears to be present in almost every county in Iowa and Minnesota. For the first several years, the only confirmations in Illinois were in northern counties and one far western county (Hancock). Over the past few years we have received samples from central Illinois which were either confirmed or highly suspected of infection with the bur oak blight pathogen.