No. 3/May 11, 2015

Modified Growing Degree Days (Base 50°F,┬áMarch 1 through May 7)
Insect development is temperature dependent. We can use degree days to help predict insect emergence and activity. Home, Yard, and Garden readers can use the links within this article with the degree day accumulations listed to determine what insect pests could be active in their area.

*UPDATE - Illinois Invasive Awareness Month Symposium
We have reached our on-site capacity for the for the Illinois Invasive Species Awareness Month (ISAM) Symposium Thursday, May 28. The symposium will be broadcast online and will be available later as a recording thanks to University of Illinois Extension and Illinois Natural History Survey, a division of the Prairie Research Institute at University of Illinois.

Fire Blight
Fire Blight symptoms started to appear on several rosaceous hosts this past week. The majority of the foliage on the trees that I observed appeared healthy, with only a few branch ends affected by the disease. Warm temperatures followed by moist conditions that occurred during flowering lead me to suspect that more branches will likely be affected as we progress through the month of May.

Anthracnose on Herbaceous Ornamentals
Anthracnose is the name given to group of plant diseases caused by related genera of fungi. Anthracnose diseases can affect both trees and herbaceous ornamental trees. The University of Illinois Plant Clinic has diagnosed both trees and ornamental plants with anthracnose this year.

Emerald Ash Borer
Emerald ash borer should be emerging in southern Illinois this week. It will probably emerge in central Illinois next week, and in northern Illinois in early June. The accompanying map from May 2 shows the 450 degree day base 50 degrees F area of Illinois and surrounding areas at that time. Emerald ash borer adults emerge at 400-500 DD.

Bridalwreath Spirea and Insect Management
Bridal wreath spirea, or Vanhoutte spirea (Spiraea x vanhouttei), is blooming in throughout the state. This is a major phenology plant in Don Orton's book Coincide. With phenology, stages of plant development (usually bloom time) are used to predict stages in pest development.