No. 9/June 25, 2018

Modified Growing Degree Days (Base 50°F, March 1 through June 21)
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 in this article with the degree day accumulations to determine what insect pests could be active in their area.

Swede Midge a Threat to Illinois Crucifers
The swede midge was confirmed for the first time in Illinois last July in a homeowner garden in Cook County. This insect is a serious pest of cruciferous plants such as cabbage, cauliflower, and broccoli. We know very little about its potential distribution in Illinois at this point. Swede midge is widespread in the northeastern U.S. An invasive pest, it is native to Europe and Southeast Asia.

Field Horsetail – A Unique but Aggressive Plant
Field Horsetail (Equisetum arvense) is an herbaceous perennial with a bottlebrush appearance. Other names include bottle-brush, snake-grass, horsepipes, and scouring-rush.  This primitive native to North America is mostly leafless yet the cone-bearing stem has been widely used to scour or clean pans, to serve as sandpaper, and to polish metal as horsetail is rich in silica. 

Potato Leafhopper
Potato leafhoppers (Empoasca fabae) are pests in nurseries and landscapes that cause injury by using their piercing-sucking mouthparts to feed on plant fluids.  They feed on oak, maple, red mulberry, red bud, cottonwood, birch, apple, dogwood, hawthorn, wafer ash, euonymus, black locust, and cherry, with red maple being a favorite.  They can cause aesthetic injury to leaves and heavy feeding can reduce the annual growth of the plant and the growth of new shoots.

Guignardia Leaf Spot
Boston ivy and Virginia creeper are two reliable vines that are adaptable to a variety of sites and conditions. Both vines are relatively problem-free. However, Guignardia leaf spot will occasionally blemish their foliage. The pathogen that causes Guignardia leaf spot is closely related to the pathogens that cause black rot of grapes and horse-chestnut leaf blotch.

White Pine Decline
Several eastern white pine samples have made their way to the U of I Plant Clinic this spring. The samples all arrived with similar descriptions of overall symptoms, "Dying trees with thinning, yellowing and browning needles." These samples are always somewhat frustrating because they usually lack any pathogens to explain the symptoms. Incubated needles and branches rarely produce any diagnostic clues. The lack of pathogen(s) leads us to attribute the symptoms to white pine decline, a condition caused by an environmental or abiotic stress