No. 3/May 7, 2012

Weather & Insect Emergence
The weather over the last week has varied in its effect on insect development throughout the state. Insect development is generally governed by a base temperature of about 50 degrees F. Based on growing degree days with a base temperature of 50 degrees F, southern Illinois is about two and one-half weeks ahead of the historical average and central Illinois is two weeks early. Northern Illinois is about one and one-half weeks early.

Scouting Watch
Emerald ash borer, Bagworm, and Silverleaf Whitefly are discussed.

Eastern Flower Thrips
Large numbers of eastern flower thrips, Frankliniella tritici, are present in central Illinois. This insect primarily overwinters in the southern U.S. and typically migrates into Illinois in the spring. They are major pests of greenhouses and outdoor flowers. These thrips cause severe distortion of the berries of strawberry.

Watch out for Impatiens Downy Mildew
In October, 2011, there were several reports of impatiens downy mildew (IDM) on garden impatiens (Impatiens walleriana). This disease was first reported in the U.S. in 1942, but late last season was confirmed on impatiens in coastal southern California, northeastern Illinois, northern Indiana, Cape Cod in Massachusetts, Long Island and upstate New York.

Chickweed is Struttin' Its Stuff
There is certainly no shortage of chickweed in Illinois this spring. The mild winter and warm conditions early on have likely led to the increased populations we are seeing. Common chickweed (Stellaria media) is a cool-season annual (also known as a winter annual) member of the Pink family (Caryophyllaceae) that reproduces by seeds.

Spruce Needle Rust
The plant clinic has received a couple of Spruce samples that were found to be infected with Spruce Needle Rust (Chrysomyxa spp.). Several species of fungi belonging to the genus Chrysomyxa are known to cause rust on spruce. Most Chrysomyxa species are heteroecious and require more than one host to complete their life cycles.