No. 7/July 16, 2021

Twospotted Spider Mites
Twospotted spider mites (Tetranychus urticae) are herbivorous mites that feed on a broad range of deciduous trees and broadleaf evergreens. In cool or damp weather their populations are controlled naturally by fungi and other pathogens. However, their populations flourish in hot, dry conditions.

June 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

Weedy Vines Commonly Found (and Confused) in the Landscape
Vining plants are often desirable in the home landscape. They cleverly disguise carefully placed trellises and their form seems to take on a life of its own. Some vines have been known to cover trees, poles, cars, and even slow moving animals I suspect. Quite a few vines are considered weedy by most. Many times, these weeds are successfully controlled and the story ends there. Too often however, an unidentified, cute, little vine is allowed to flower and develop seeds or rhizomes. Fast forward a few years, and its population can be out of control. Perhaps morningglory was intentionally seeded into a site from a pretty, little seed packet. You’ll get your money’s worth when this annual produces a bounty of seeds for future years! But here again, if (when) these cute plants tend to wear out their welcome, then efforts will be underway to eradicate them.

Common Spruce Diseases
As Diane Plewa noted in her June 2021 Plant Clinic Sample Summary, the U of I Plant Clinic continues to receive numerous evergreen samples infected with needle blight and needle cast diseases. These types of samples, and reports of sick/dying spruce trees are common occurrences each growing season. The following are the most frequently diagnosed spruce diseases by the plant clinic:

Not Your Household Vinegar
Do you find that social media opens up a lot of “how to’s” or DIY’s on weed control? Vinegar comes up often as an herbicide. In truth, vinegar does work as a herbicide, but not your average household vinegar. Most household vinegar solutions are at 5% acetic acid, where a herbicidal vinegar will have a range of 10-30% acetic acid. These higher percentages are more effective in controlling new seedlings and growing points than the household vinegar.