No. 5/May 30, 2017

Modified Growing Degree Days (Base 50°F, March 1 through May 25)
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.

Viburnum Leaf Beetle Update
In the May 8th issue of the Home, Yard and Garden Pest Newsletter, we shared that initial reports of viburnum leaf beetle activity were observed in Illinois. Since that time, we have continued to receive reports out of Cook and DuPage counties of severe viburnum leaf beetle larval feeding, resulting in the defoliation in several areas of those counties.

Every spring, I am asked about Goutweed, also known as Bishop's Weed or Snow-on-the-Mountain (Aegopodium podagraria).  This plant isn't your typical weed but it is an aggressive groundcover that can be invasive and difficult to control.

Sickly Spruce
Does your spruce tree look like it has seen better days? Well, judging by the number spruce samples sent to clinic, you are not the only one. Each spring, the U of I Plant Clinic receives numerous calls, emails, and samples regarding sick/dying spruce trees. The most commonly diagnosed spruce diseases by the plant clinic are discussed in this article.

Large flights of armyworm moths have been reported this spring. Be watchful for armyworms and their damage in turf. When they are numerous, they can eat off every blade of grass in several thousand square feet of turf per night. In the evening you have nice, green turf, and in the morning all you have are crowns and thatch.

Viburnum Leaf Beetle
Obvious damage by viburnum leaf beetle is being found in northern Illinois. Eggs overwinter and hatch in May into yellow to brown larvae with black dots which feed on the undersides of viburnum leaves. The feeding damage is very characteristic as both the larvae and adults eat elongated oval areas of leaf tissue between lateral veins, creating an interesting angling damage pattern on heavily attacked leaves. Heavily attacked shrubs are defoliated, and those defoliated two to three years in succession are likely to die.

Cinara Conifer Aphids
Aphids in the genus Cinara are typically orange, tan, brown or black. The green spruce aphid is actually orange. Some have white markings. They tend to be long-legged and more active than other aphids causing some people to casually identify them as spiders. Others flatten against the stem, allowing them to overlooked as fascicle scales. Some species are one-sixth inch long, making them larger than most aphids.