No. 3/June 7, 2023

Modified Growing Degree Days
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.

Rose Slugs
We've had several reports of bristly rose slug causing rose foliage to be lacelike. The green larvae are more numerous on the undersides of the leaflets. Although causing window-feeding when young, the larger larvae eat holes in the leaflets and even cause defoliation.

Woolly Beech Aphid
Large populations of woolly beech aphid, Phyllaphis fagi, have been reported on European beech trees this season. Beech trees are the only hosts for this aphid. The woolly beech aphid gets its name because the body is covered with waxy wool-like filaments. These aphids are gregarious and tend to congregate primarily on the undersides of leaves. Often large numbers of the molting or cast skins will be attached to leaf hairs, which gives the leaf a whitish appearance. The woolly beech aphid has piercing-sucking mouthparts, which are used to remove plant fluids. However, woolly beech aphid is not considered an economic pest because beech trees, especially large specimen types, can sustain large populations without suffering any injury. Large populations of woolly beech aphid can, however, produce tremendous amounts of honeydew, a clear, sticky liquid that may attract wasps, ants, or yellowjackets. In addition, the honeydew serves as an excellent growing medium for black sooty mold fungi. Black sooty mold fungi can detract from the aesthetic appearance of a beech tree and most importantly can reduce the production of food via photosynthesis by blocking the entry of light.

Springtime Broadleaf Weed Control in Turf
Actively growing broadleaf weeds can be controlled and prevented with proper practices. Weed invasions can be minimized through proper turfgrass management. Consider use, site, and budget when selecting an appropriate turfgrass. Follow correct selection with appropriate mowing, watering, fertilizing, and cultivating; all can lead to a dense, healthy turf. Reduced weed populations result because weeds have difficulty becoming established in healthy, competitive turf.

Abnormal Ginkgo and Beech Trees
Recent high temperatures have reached into the 90s. That makes it easy for us to forget that we had some very cold nights in late April and early May. Overnight lows dipped into the 20s injuring some plants that had broken dormancy and started to leaf out. Frost injury may explain the odd appearance of some ginkgo and European beech trees. I’ve received several reports of thin, sparse canopies and deformed leaves on both species.

It’s Dry Out There!
You probably didn’t need this newsletter article to alert you to the fact that things are getting a bit dry outside. Much of Illinois has been in a dry pattern since mid-April. Trent Ford, Illinois State Climatologist, recently wrote a detailed blog post on the Increased Risk of Drought Conditions in Illinois. The most recent U.S. Drought Monitor, published June 1, 2023, listed 30.62% of Illinois under moderate drought, and 44.8% as abnormally dry. With above-average temperatures in the forecast and no rain in sight, I expect many garden hoses and watering cans will be working overtime.