Northeast WI Forest Health

Look For Spongy Moth Egg Masses – Larger Outbreak Possible in 2023

Posted on by kirsten.biefeld

By: Bill McNee, DNR Forest Health Specialist, Oshkosh

bill.mcnee@wisconsin.gov or 920-360-0942

Three tan-colored spongy moth egg masses on a single tree branch in Walworth County.

Three spongy moth egg masses on a branch in Walworth County. Photo Credit: Bill McNee, Wisconsin DNR

Now that spongy moth* (formerly known as gypsy moth) egg laying is complete for 2022, it’s a good time to look for and dispose of egg masses produced by adult moths over the past two months.

Spongy moth egg masses are tan-colored lumps about the size of a nickel or quarter, and are found on trees, buildings and other outdoor objects. They may also be found in protected places such as firewood piles and birdhouses. Newly produced egg masses will feel firm and appear darker in color than older egg masses, which appear faded, feel spongy and do not contain viable eggs. The current-year egg masses will not hatch until next spring.

In 2022, Wisconsin’s spongy moth population grew for a third consecutive summer due to favorable weather conditions and limited caterpillar mortality from diseases. The outbreak was most dramatic in opposite ends of the state. In southern and southeast Wisconsin, several thousand oak-dominated acres were heavily defoliated and very large numbers of property owner reports were received by DNR staff. In Bayfield County, about 80,000 acres of rural defoliation was reported from aspen-dominated forests. Smaller patches of defoliation were also reported from several other counties. Continue reading “Look For Spongy Moth Egg Masses – Larger Outbreak Possible in 2023” →

Acorn Weevils Make Acorns Float

Posted on by brenna.denamur

Article By: Linda Williams, DNR Forest Health Specialist, Woodruff
Linda.Williams@wisconsin.gov or 920-360-0665

Have you seen small round holes in acorns? These holes are a sign of acorn weevil damage that can occur in all Wisconsin oak species.

In a pile of brown and tan acorns, two have small round pencil-tip sized holes caused by acorn weevil larvae burrowing out from the inside.

Two acorns show exit holes of acorn weevils. / Photo Credit: Wisconsin DNR

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Managing Damage By White Pine Weevil

Posted on by patricialindquist

Article By:  Linda Williams, DNR Forest Health Specialist, Woodruff
Linda.Williams@wisconsin.gov or 920-360-0665

Tree damage from white pine weevil is noticeable across Wisconsin this time of year. White pine weevils attack several different Wisconsin species, including eastern white pine, jack pine and spruce.

Adult weevils lay their eggs on terminal leaders in the spring. After the eggs hatch, larvae bore into the terminal and begin feeding downwards just under the bark which can result in the killing of a 1 to 2-feet section of the terminal leader as they feed. Terminal leaders will often have a wilted or “shepherds crook” appearance, and they will turn rusty red to brown late in the fall season. These dead terminal leaders will often break off during the winter.

A white pine tree with a cluster of dead twigs caused by a white pine weevil attack.

Dead terminal leader caused by a white pine weevil attack on a young white pine.
Photo Credit: Wisconsin DNR

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Young Oaks Defoliated By Oak Slug Sawfly

Posted on by patricialindquist

Article By: Linda Williams, DNR Forest Health Specialist, Woodruff
Linda.Williams@wisconsin.gov or 920-360-0665

The oak slug sawfly (Caliroa quercuscoccineae), sometimes called the scarlet oak sawfly, has the appearance of a small, slimy slug. Its slime helps it stick to leaves it feeds on. The oak slug sawfly’s tiny larvae feed in groups on the undersides of oak leaves, scraping out the green material from between the veins of the leaves. The upper leaf surface is usually left intact, creating a “stained glass window” look. Oak slug sawfly has the ability to completely defoliate leaves before dropping to the ground to pupate.

Two oak leaves eaten by oak slug sawfly larvae left with brown discoloration on the leaf and translucent patches.

Oak slug sawfly larvae cause defoliation on oak leaf after feeding.
Photo Credit: Wisconsin DNR

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Diplodia Shoot Blight vs. Red Pine Shoot Moth

Posted on by patricialindquist

By Todd Lanigan, DNR Forest Health Specialist, Eau Claire, Todd.Lanigan@wisconsin.gov or 715-210-0150

Scattered damage to new red pine shoots has been observed across many counties this summer. With the intermittent rains during the summer, the first thought was that Diplodia shoot blight, a fungal disease, was causing the damage. Upon a closer look, some of the shoot mortality is caused by the red pine shoot moth. From a casual glance, these two problems will look the same, so you really need to take a closer look. 

If Diplodia causes the shoot mortality, the shoot usually forms a shepherd’s crook. And, in time, you will find the fungal fruiting bodies on the needles, especially if you look under the needle sheath (covering) at the base of the needles.

Shepherd’s crook caused by Diplodia shoot blight. Photo Credit: Elizabeth Bush, Virginia Polytechnic Institute and State University, Bugwood.org

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Redheaded Pine Sawfly Numbers Remain Elevated In Northeastern Wisconsin

Posted on by patricialindquist

Written by: Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov or 920-360-0665. 

For the third year in a row, colonies of redheaded pine sawfly have been noted on understory red pine in northern Wisconsin, with the most reports coming from Vilas and Oneida counties.

Redheaded pine sawfly larvae feeding on red pine needles. Note the needle stubs where they have eaten nearly to the base of the needle. Photo Credit: Wisconsin DNR

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White Pine Branch Tips Red And Wilting

Posted on by patricialindquist

Written by: Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov or 920-360-0665. 

White pine trees in many counties in northeast and northcentral Wisconsin have developed rusty-colored wilting needles on outer branch tips scattered throughout the tree’s crown. These dead branch tips are associated with the feeding by white pine bast scale. The scale is a tiny insect that inserts its straw-like mouthpart into the twig to suck sap from the outer layers of phloem called bast. Damage has been observed on trees over 20 feet tall this year. 

Branch tips on this white pine indicate a problem with bast scale and the disease Caliciopsis. Photo Credit: Wisconsin DNR

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Pear Slug Sawfly Defoliation: Treatment Tips

Posted on by patricialindquist

Written by: Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov,  920-360-0665. 

Pear slug sawflies (Caliroa cerasi) feed by scraping off the upper layer of the leaf, leaving the veins and the lower leaf surface. Severe defoliation has been observed and reported recently on crabapple, apple, mountain ash and serviceberry in Oneida, Forest and Oconto counties. The first generation occurs earlier in the summer, so the larvae and defoliation seen now are due to the second generation of the insect, which is larger than the first generation.

Pear slug sawfly larvae feed by scraping off the upper layers of the leaf. Photo Credit: Wisconsin DNR

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Oak Leaves Turning Brown? There Are Several Reasons This Year.

Posted on by patricialindquist

Written by: Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov or 920-360-0665 

Oak wilt symptoms are active right now, but so are several other oak issues that may be mistaken for oak wilt symptoms. Issues including Tubakia leaf spot, Botryosphaeria canker, kermes scale damage and mite damage are all causing problems and may be mistaken for oak wilt.

Oak Wilt Leaf Symptoms

Trees in the red oak group (those with points on their leaves) that became infected with oak wilt in the spring will suddenly start to drop their leaves in July and August. Trees that were infected later in the high-risk period (April 15 – July 15 in northern Wisconsin) may start to drop their leaves later, in September or even into October.

Leaves dropping from oak wilt trees can be fully green, tan or a water-soaked, greenish color away from the petiole (leaf stem). There will often be an area that is still green near the petiole, even though the leaf has fallen to the ground. Wilting leaves typically start near the top of the tree and progresses downwards.

Recommended control measures depend on if you have just one tree actively wilting (and no others have died in past years) or if you are dealing with established pockets that have been present for more than a year. Contact your regional forest health specialist to discuss these control options if you think you have oak wilt.

Leaves dropping from trees dying from oak wilt often are brown or water-soaked on the outer portions of the leaf with green still found near the base of the leaf. Photo Credit: Wisconsin DNR

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Oak Wilt Symptoms Visible Now

Posted on by patricialindquist

By Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov or 920-360-0665. 

Symptoms of oak wilt are showing up. Look for leaves that suddenly wilt and drop from the tree. Oak wilt is a non-curable, fungal disease specific to oaks. Trees in the red oak family will die quickly from this disease, while trees in the white oak family will die more slowly, with a branch or portion of the crown becoming infected. 

This tree is actively wilting from oak wilt infection and will drop most of its leaves within about 4-6 weeks.

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