No. 7/June 6, 2016

Modified Growing Degree Days (Base 50°F, March 1 through June 2)
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 below with the degree day accumulations above to determine what insect pests could be active in their area.

Giant Hogweed? Maybe its Cow Parsnip, Poison Hemlock, or Purple Angelica...
This week, we have received a couple of calls regarding the possibility of giant hogweed. Now is the time of year when giant hogweed starts to bloom. As one of our most unwanted invasive species in Illinois, we definitely want to know if there are any populations. But, please remember, giant hogweed can easily be confused with several other plants. These look-a-likes are also being observed across the state at this time.

Mower and Weed-eater Damage
Most tree professionals will tell you the worst plant to be grown around trees is turfgrass. It's not that turfgrass is all that bad for trees, though in nature you seldom find manicured lawns growing around native stands. While the turfgrass may compete for nutrients and waters, it's the mower and weed-eaters that cause the most injury.

Dutch Elm Disease
Dutch elm disease (DED) is a destructive wilt disease caused two closely related fungi, Ophiostoma ulmi and Ophiostoma novo-ulmi. Since its introduction to the United States in the 1930s (Illinois 1950s) DED has killed millions of native elm trees. American elm (Ulmus Americana) and red elm (Ulmus rubra) are very susceptible. Asiatic elms, Lacebark elm (Ulmus parvifolia) and Siberian elm (Ulmus pumila), are the most resistant species.

Apple Scab
Apple scab is a common fungal disease that affects apple and crabapple trees. Initial infection occurs in spring during flowering, followed by repeating cycles of secondary infections that continue through the growing season.

Viburnum Leaf Beetle
Obvious damage by viburnum leaf beetle is being found in northern Illinois. This is an exotic, invasive species common in areas of the northeastern U.S. It has recently been found in Illinois.

May Beetles
There are many species of the genus Phyllophaga, also known as true white grubs or May beetles that occur in Illinois. Their larval stage is one of the genera known as white grubs that feed on turfgrass roots, but unlike other white grubs in turf, true white grubs also feed on dead organic matter. For that reason, they are commonly found in flower beds, under dead logs, and in mulch causing no apparent damage.