All maple producers know that without healthy maple trees, you would have no sap or syrup. A wide range of pests and diseases can impact your sugarbush, so it is important to know how to recognize the symptoms and what to do in response.
For our July Maple Hour, Wisconsin Department of Natural Resources Forest Health Specialist Paul Cigan joined us to talk about common sugarbush pests and diseases. Here are some highlights from Paul’s presentation, which you can watch in full at the bottom of this page.
Many forest health issues result from summer insect outbreaks. Wisconsin has long been home to insects that feed on maples and can damage them if present in large numbers. Other insects are new arrivals whose long-term impact is not yet clear. Paul explained that green-striped mapleworms, maple petiole borers, and spongy moths have all been active this summer, especially in northern Wisconsin. Fortunately, these three insects are so far not causing major problems for maple syrup production.
Like spongy moths, forest tent caterpillars normally have dramatic outbreaks every 6 to 10 years. But Wisconsin has not seen a surge of forest tent caterpillars since 2001, so we are overdue. Paul encouraged sugarmakers to report any sightings of these caterpillars to your local DNR forest health specialist—the population usually starts to rise for a year or two before the worst of the outbreak, so early warnings will give producers time to prepare.
Sugar maple borers and ambrosia beetles are two species that can have larger impacts on sap production. Whenever you thin your stand, you should remove trees with signs of sugar maple borer. Ambrosia beetles are fairly uncommon in Wisconsin, but they have been spotted recently in a sugar maple stand in the UW Arboretum in Madison. We don’t yet know which management strategies are best for controlling ambrosia beetles.
In addition to insects, diseases such as eutypella canker, sapstreak disease, and armillaria root disease can affect the health of your sugarbush. You can prevent or slow their spread by following sound forestry practices when harvesting timber, Paul explained. Remove or debark stumps, don’t cut off single stems unnecessarily, and practice good sanitation.
Although keeping track of all these possible stressors might feel overwhelming, one overarching strategy can help increase your sugarbush’s resilience against them all: encourage diversity in terms of species (at least 25% non-maples), age classes, and size classes.
Watch the full discussion to learn how to spot each insect and disease, as well as invasive earthworms and tree damage caused by mammals. If you see a health issue in your woods, you can reach out to the DNR Forest Health Specialist for your region for a free consultation or site visit. If a lab test is necessary to diagnose the problem, contact the UW Plant Disease Diagnostic Clinic or UW Insect Diagnostic Lab. You can also learn more about forest health on the DNR website.
