No. 4/June 1, 2021

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

Brood X Periodical Cicadas
Brood X periodical cicadas (Magicicada spp.) are emerging now in Edgar, Clark, Crawford and Vermillion counties and will continue to emerge until late-June. This year we can see two species of periodical cicadas, the pharaoh cicada (Magicicada septendecim) and Cassini 17-year cicada (Magicicada cassinii). These species can be differentiated by both their size and markings. The pharaoh cicada is the larger of the two and has thick orange stripes across the underside of its abdomen. The Cassini 17-year cicada is much smaller and the underside of its abdomen is all black.

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.

Use of Herbicide in Natural Settings
To some, the idea of using herbicides in “natural” settings may seem a little ironic, but in fact herbicides are a useful and valuable tool for land owners and managers. Natural areas including woodlands, prairies, and even hedgerows in urban landscapes can be overtaken by invasive weeds – which are also “natural”. Weeds can alter ecosystems and rob sunlight, water, and nutrients from desirable plants which affects their growth and yield. In this article, we will discuss the pros and cons of herbicide use in these areas, alternative methods of weed control, and common application methods. Of course we typically recommend that non-chemical methods be implemented first before resorting to using herbicides.

Powdery Mildew on Common Ninebark
Many view dry conditions as being unfavorable for fungal pathogens. While this is often true, some fungal diseases, such as powdery mildew, thrive under dry, humid weather. The most recent U.S. Drought Monitor has roughly a quarter of Illinois categorized as abnormally dry to severe drought. The northeast counties are under the latter.

Slime Mold on Mulch
The recent yet brief taste of summer weather brought about the appearance of slime molds on mulch beds. Slime molds are harmless organisms. However, I will admit they can have a somewhat off-putting appearance akin to vomit. I captured the following photo during a recent trip to a playground with my kids.

Watering during drought can reduce stress in trees, potentially reducing long-term injury from frost damage and diseases
Don’t fret, but some trees may be showing damage from the late frost we received in May for several months to come. Some additional watering during the hot dry months of summer, and the affected trees will be well on their way to being beautiful specimens.