No. 3/May 19, 2021

Modified Growing Degree Days (Base 50⁰ F, March 1 through May 16)
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.

First Quarter 2021 Plant Clinic Sample Summary
The Plant Clinic remains open. We are currently operating with reduced staff and are only in the lab as needed for diagnostics and other lab work. We may not be able to answer or return phone calls in a timely manner; MWF are the best days to contact us due to staffing schedules. You can also email us at

Lilac / Ash Borer
Lilac borers (Podosesia syringae; also called ash borer) feed on lilac, ash, privet and other members of the olive family. Adult moths resemble paper wasps in appearance and behavior. They are about 1 inch long, slender, with dark brown bodies and yellow banding. They are active during the day and flex their abdomens as they walk.

Quackgrass Identification and Control
Quackgrass (Elytrigia repens) is a coarse textured, cool-season perennial grass that has surely been enjoying the cool temperatures and timely rains we’ve had this growing season. When we see lush new growth of our cool-season turfgrasses, we can often find quackgrass growing happily nearby. It spreads by seeds and long, light-colored rhizomes and aggressively forms patches. Quackgrass can be difficult to eliminate, especially from finer-textured turfgrasses. If you haven’t done so already, scout your landscapes for this weed and plan your control tactics.

Unwanted Tree Seedlings in the Lawn and Landscape
The maples are currently on a mission to reforest the Earth. The ash, cherry, and mulberry trees are often on the same mission. For some, birds help spread the seed. For the maples, all that is needed is wind and gravity to blow the samaras to the ground. You’ve seen them and certainly played with them as a kid – the helicopters or whirlygigs or whatever you called them. This morning I noticed they cover my sidewalks, lawn, and landscape beds. In a few days, there will be baby maples everywhere and much work to be done to reclaim the landscape.

Avoiding Boxwood Blight
Boxwood blight is a fungal disease that continues to pose a serious threat to boxwood plants in nursery production and landscapes. To date, we have only detected isolated incidents of boxwood blight in Illinois. Our goal remains to avoid introducing the pathogen, and to eradicate any future detections. If you maintain a landscape with existing boxwood shrubs, then boxwood blight should be high on your list of diseases to avoid. It is much easier to prevent a boxwood blight introduction than to control it. Start by knowing the common boxwood blight symptoms and signs highlighted in Plant Clinic Fact Sheet: Boxwood Blight Detection. You should be familiar with the common boxwood pests that have symptoms that might be easily confused with boxwood blight: Boxwood Blight Look-alikes.

Crown Rust of Common Buckthorn
May is Illinois Invasive Species Awareness Month. Common buckthorn (Rhamnus cathartica) was one of the first invasive species that I was introduced to. Readers in the northern portion of the state are likely to be familiar with this pest, as it has invaded and overtaken woodland areas by easily out-competing native plants for light and moisture. I learned firsthand how invasive and destructive this plant was during a high school class that used a Kane County Forest Preserve as a "classroom." Since then, I've spent countless hours clearing common buckthorn to reclaim woodland habitat. Buckthorn puts up a fight with every step from cutting to dragging and trying to load it into a brush chipper.

Rabbits in the Landscape
I look forward to my local FFA Chapter’s annual greenhouse sale. It’s a great opportunity to spruce up the front of the house with flowers. I have hanging baskets across the porch and several planters filled with a variety of annuals. I enjoy the beauty of the flowers and the color they give the yard. This year, not even a week after planting, I noticed several planters that the plants were broken, missing, or chewed on. I have two little boys that love play in the dirt, and so I honestly just chalked it up to them getting carried away playing. After watering these planters daily, I noticed the plants getting smaller and found rabbit scat in the planters. I finally found the culprit. I began to feel like Mr. McGregor from Peter Rabbit and wanted full-on warfare with them. It not only financially hurts as I watched several dollars be eaten up, but I also lost the beauty of all the flowers.