No. 4/May 31, 2019

Modified Growing Degree Days (Base 50⁰ F, March 1 through May 30)
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.

Brownheaded ash sawfly
Brownheaded ash sawfly larvae (Tomostethus multicinctus) are native insects that are currently defoliating ash trees in northern Illinois.  These larvae are greenish-white to yellowish-white and look somewhat like caterpillars, except that they have six or more pairs of prolegs.  They have green heads with obvious small black eyes.

Catchweed Bedstraw is Catching On to a Landscape near You
I’m starting to see more and more catchweed bedstraw lately, which saddens me.  Sure, it has somewhat of a cute appearance.  But once you’ve hand pulled an unwanted, sticky patch of it, you will forever have a disdain for this plant.

Sycamore Anthracnose
You have likely noticed that many sycamore trees have been slow to leaf out this spring. Until this past week, most of the sycamore trees in central Illinois have remained bare, with no signs of life. This year has been particularly severe for sycamore anthracnose. Infections from this fungal disease occur almost every spring. However, the severity of the infection is dependent on the weather. This spring’s predominately cool and wet conditions have greatly favored disease development.

Why are Yew so sad?
Yew plants are fairly pest-free once established into a landscape, and can be wonderful evergreen additions to the right area. However, we’ve seen several yew samples at the Plant Clinic in the last few weeks. Most of them come with pictures or descriptions of plants with needles turning bright yellow, then browning and eventually falling from the plant. When examined under the microscope, no pathogens or insect pests are found. Instead, corky bumps or blisters are observed, usually on the underside of the needle. These can be seen with the naked eye, though they may appear as spots.

Cancellation of 12 Neonicotinoid Products
The Environmental Protection Agency (EPA) published a notice in the Federal Register on May 20, 2019, stating that the registrations for 12 neonicotinoid insecticides have been canceled.  A list of the insecticides canceled is shown in Table 1, taken from the Federal Register.