No. 15/August 27, 2012

West Nile Virus
The hot, dry summer has apparently been responsible for higher levels of West Nile virus earlier this year in Illinois. The virus is reaching levels about a month earlier than is typical. As it normally builds from mid-August through the fall, this early increase followed by human cases makes it likely that its impact will be much higher than recent years. This increased level makes it important to protect landscape workers and others involved in outdoor activities.

European Paper Wasp
European paper wasp, Polistes diminula, has been identified in Urbana in central Illinois. This wasp has been in northern Illinois for several years. In North America, it is found in southern Canada and the northern U.S., being common in Ontario, Michigan, Ohio, and Wisconsin. It has not been found south of southern Virginia. In the eastern hemisphere, it is native to southern Europe and Asia and northern Africa. It will surely continue to spread farther south in the U.S.

Downy Mildew of Impatiens Is Back in 2012
This week, the U of I Plant Clinic has confirmed downy mildew of impatiens (Impatiens walleriana) in Cook County. It is apparent that the recent rains and cooler night temperatures provided the perfect environment for disease infection. Earlier this year, in HYG issue #3 I warned readers to watch out for this unbelievably destructive disease.

Bleeding Canker on European Beech
Bleeding Canker is a potentially lethal disease to mature European Beech trees (Fagus sylvatica). Researchers at Cornell University have been working extensively with this disease and have identified three closely related species of Phytophthora that are involved. Phytophthora plurivora, P. pini and P. citricola all cause similar bleeding canker symptoms.