It’s time for River Mathieu and Tim Shively to put all their education and research to work.

Mathieu and Shively are the newest additions to the Wisconsin Department of Natural Resources (DNR) Forest Health team. Both started on June 30, filling Forest Health Specialist vacancies.

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Anthracnose is a common disease of hardwood trees during cool, wet spring seasons. Some parts of Wisconsin have been cooler and wetter than others this spring, so anthracnose damage may be patchy.

Ash, maple, white oak, sycamore and walnut are the most impacted tree species. Each species has its own species of anthracnose that infects it, but if weather conditions are right, then we tend to see damage on multiple species.

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Armillaria is a root-rot pathogen that usually lives quietly under the soil. But when trees experience stress, the fungus can attack and colonize the roots of the stressed tree.

Armillaria can infect many different species of trees, and trees of any age or size, but the result for the tree is usually a slow decline and eventual death.

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Colorful “bull’s-eye” spots on maple leaves are maple eyespot galls, caused by the tiny ocellate gall midge (Acericecis ocellaris).

The adult midge lays eggs on the underside of the leaves. Once the eggs have hatched, the larvae feed on the leaves. That feeding causes the leaf to develop telltale colorful, concentric circles in that area of the leaf.

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Dusky birch sawfly (Croesus latitarsus) is a native sawfly that feeds on white birch and occasionally river birch and yellow birch. Larvae feed in a group at the edges of birch leaves and abandon part of the midrib before moving on to another leaf.

This defoliation is only problematic on young seedlings with few leaves. There may be two generations of larvae in a year.

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You may have seen these leathery, yellow fungi growing on recently dead red pine trees and wondered if they were what killed the tree. The short answer: No, they did not kill the tree.

The veiled polypore (Cryptoporus volvatus) is a decay fungus that grows on the bark of red pine in the year after they die. They can be found anywhere on the trunk of the tree.

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Scattered maple trees across parts of the Northwoods have produced heavy seed crops this year.

When trees produce so many seeds, it reduces the amount of energy available for producing leaves. As a result, those leaves can appear smaller and off-color into the summer. With fewer leaves produced, these trees will continue to look very thin throughout this year’s growing season.

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Euonymus caterpillars (Yponomeuta cagnagella) made a dramatic appearance in June, webbing and defoliating Euonymus shrubs in several counties.

Multiple species of Euonymus may be attacked, including spindle tree, winged (e.g., burning bush), eastern wahoo, winter creeper and others.

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If you’ve noticed tamarack trees with tan or light-brown foliage, you’re probably seeing the work of the larch casebearer.

As foliage began to expand this spring, the caterpillars of this invasive moth became active and began to feed. The tiny caterpillars mine out the needles of tamarack and use them as “cases” to protect themselves, hence their name.

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Fallen maple leaves have been observed under Wisconsin maple trees since late May.

The fallen leaves are typically of normal shape, size and color, but have a darkened petiole stub (i.e., leaf stem) remaining. A closer examination of the petiole may reveal a hollow feeding tunnel containing tiny larvae of the insect responsible for the damage inside: the maple petiole borer.

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White grubs, the larvae of Wisconsin’s native May/June beetles (Phyllophaga spp.), can cause significant damage to forest plantings.

To help those who plan to plant seedlings and saplings, the Wisconsin Department of Natural Resources’ (DNR) Forest Health team has produced a fact sheet on white grubs, aimed specifically at forest plantings.

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In North Central Wisconsin, some Eastern white pine had needles that turned a bright yellow color in early June, then quickly dropped from the trees by the end of June.

These trees will now look rather thin throughout the summer, until new foliage can fully expand and start to fill in the crown. Most damage has been noted in Oneida and Vilas counties, with scattered instances in other counties.

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Plants that are pokey, viny or quick to spread across the landscape sometimes seem alarming when you discover them in your backyard or woods, or even when you spot them along the highway.

Wild cucumber has all these characteristics, and its growth rate has been quite prolific in some parts of Wisconsin again this year. But all of this is not as ominous as it seems.

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The Winsome fly (Istocheta aldrichi (Mesnil)), part of the Tachinidae family, is a parasitoid of the invasive pest Japanese beetle (Popillia japonica).

The Winsome fly was introduced in 1923 in New Jersey as a biological control agent of the Japanese beetle, six years after the Japanese beetle was accidentally introduced in the United States.

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Woolly elm aphids (Eriosoma americanum) are a minor pest of American elm. The aphids’ feeding causes leaves to curl at the edges and develop a characteristic wrinkled appearance.

Uncurling the leaves exposes many pale gray aphids on the underside of the leaves, which are protected by the rolled leaf.

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