BLOOMINGTON, Ill. — Poet George Herbert once wrote, “Storms make oaks take deeper root.” Any homeowner who is fortunate to have an established oak will most likely rave about how durable the tree is. However, University of Illinois Plant Diagnostic Outreach Specialist Diane Plewa has concerns for our beloved oak trees not being able to withstand the barrage of diseases.
Some common oak diseases are aesthetically unpleasant, while others can pose a serious threat to the health of the tree. An emerging disease in Illinois, bur oak blight, has been more prevalent in samples at the Illinois Plant Clinic in the last few years; both in the number of samples and concerns expressed by tree owners. The clinic reports that 17 bur oak samples were either confirmed or suspected for blight in 2016. The disease can be difficult to diagnose since petioles that overwintered are needed to see the pathogen’s fruiting structures, and most of the time people submit the current year’s leaves. Many samples and questions regarding diseased bur oak trees are most likely tubakia leaf spot.
Sudden oak death (SOD) is a very serious, federally monitored disease that has established in parts only in California and Oregon. However, there are some diseases (including tubakia leaf spot and oak wilt) that can cause similar symptoms to SOD, says Plewa. The University of Illinois Plant Clinic encourages residents to be on the lookout since it is something they do not want to establish in Illinois.
The Plant Clinic has had increased inquiries of tree problems in general, leading them to suspect climatological stresses statewide, such as the cycle of droughts, and record-breaking wet springs. Oak diseases will be a hot topic covered at this year’s First Detector training. Course topics include Invasive Plants & Human Health, Oak Disease, Emerald Ash Borer after the quarantine, and other upcoming forest insect pests.
Illinois First Detectors training is an invaluable program educating the community on invasive threats to our Illinois landscape. The University of Illinois Extension McLean County Office [1615 Commerce Parkway, Bloomington, IL 61704] will be hosting the 2017 workshop from 9 a.m. to 4 p.m. February 9. The $40 registration includes instruction, on-site lunch, and training materials. A student rate of $25 is available. Continuing Education Units (CEUs) are also available for certified arborists. You can register at go.illinois.edu/FirstDetector12. Registration ends February 5.
— University of Illinois Extension
For more news from Illinois, click here.