West Central WI forest health

Diplodia Shoot Blight vs. Red Pine Shoot Moth

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

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

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

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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Eau Claire And Richland Counties Now Added To The Gypsy Moth Quarantine

By Andrea Diss Torrance, Invasive Insects Program Coordinator, andrea.disstorrance@wisconsin.gov, 608-516-2223

Gypsy moth has moved slowly across Wisconsin in the last 30 years since gaining a foothold in the counties along Lake Michigan. This month, the Animal and Plant Health Inspection Service and the Department of Agriculture, Trade and Consumer Protection (DATCP) determined that the invasive pest has become established in Eau Claire and Richland counties and have extended the quarantined area to include them.  This is the first time since 2015 that new counties have been added to the quarantine. Fifty-two of Wisconsin’s 72 counties are now quarantined for gypsy moth.

Wisconsin Gypsy Moth Quarantined Counties

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Balsam Gall Midge Swellings On Fir Needles

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

If you notice swollen needles or bare branches on balsam fir trees this spring, the culprit might be balsam gall midge. Adult balsam gall midges are tiny flies that lay their eggs in the developing new shoots shortly after budbreak in the spring.

Balsam fir needles with swellings caused by balsam gall midge will turn brown and drop from the tree prematurely.

Balsam fir needles with swellings caused by balsam gall midge will turn brown and drop from the tree prematurely.

Trees with late-breaking buds are less susceptible to gall midge attacks, as the buds are still tight when adult midges are laying eggs. The young larvae feed at the base of developing needles, causing needle tissue to grow around them (forming the needle gall).

The galls are green during the spring and summer but turn yellow in early fall, and infested needles drop prematurely. In the fall, the mature larvae drop to the ground, where they overwinter in the litter. By early the following spring, most of the damaged needles have fallen off, leaving bare spots along the branches where no needles are present.

Control options using insecticide applications are geared towards Christmas trees and are generally not necessary for forest trees.

Protect Oak Trees From Oak Wilt By Pruning After July, Not Before

By Don Kissinger, DNR Urban Forester, 715-348-5746 or Don.Kissinger@wisconsin.gov; Paul Cigan, DNR Forest Health Specialist, 715-416-4920 or Paul.Cigan@wisconsin.gov

The Wisconsin Department of Natural Resources (DNR) urban and forest health specialists recommend not pruning or cutting oaks from April through July to protect oak trees from the often fatal oak wilt disease.

The spring season often draws property owners outdoors to soak up rays of long-awaited sunlight, breathe in some fresh air and begin seasonal yard maintenance and cleanup projects. While spring is a time to dust off yard tools like rakes, shovels and weed clippers, when it comes to the health of oak trees, keeping those chainsaws and trimming tools a safe distance away will go a long way to ensure that your trees stay healthy for many more spring seasons to come.

Sap-feeding beetle on a diseased oak tree in Sawyer County.

Sap-feeding beetle on a diseased oak tree in Sawyer County.

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Treat Your Valuable Ash Trees Against Emerald Ash Borer

Bill McNee, Forest Health Specialist, Oshkosh. Bill.Mcnee@wisconsin.gov or 920-360-0942

Property owners with healthy, valuable ash trees should consider treating them with insecticide this spring to protect against emerald ash borer (EAB). The pest is currently the most damaging threat to trees in Wisconsin, killing more than 99% of the ash trees it infests.

Woodpecker damage during the winter is often the first sign that an ash tree is infested. Now is an excellent time to consider insecticide protection because the treatments are typically done between mid-April and mid-May once leaves begin to return.

Treatments on already-infested ash trees are more likely to be successful if the trees have low or moderate levels of woodpecker damage.

An ash tree branch with bark missing after woodpeckers attacked it while looking for larvae to eat.

This ash tree branch in West Allis has been attacked by woodpeckers looking for larvae to eat.

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Look For Gypsy Moth Egg Masses And Prepare For Hatch; DATCP Slow-The-Spread Treatments Announced

By Bill McNee, DNR Forest Health Specialist, Oshkosh, Bill.Mcnee@wisconsin.gov or 920-360-0942

Typically, gypsy moth egg masses hatch in April as temperatures warm. Now is a great time to do an egg mass inspection to look for unknown infestations and treat or remove any masses within reach. Each mass can result in 500 to 1,000 leaf-eating caterpillars.

Egg masses are tan-colored lumps and vary from about the size of a nickel to a quarter. They can be found on many outdoor surfaces such as tree trunks, the undersides of branches, buildings, rocks, fences, retaining walls, firewood piles and picnic tables.

Gypsy moth egg masses on the underside of a maple branch

Gypsy moth egg masses on the underside of a maple branch. 

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Stalactiform Stem Rust Of Jack Pine

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

Stalactiform stem rust, which occurs in the Lake States and Canada on jack pines, was recently found in western Monroe County. Before this discovery, the only place I have seen stalactiform stem rust in Wisconsin was Adams County in the mid to late 1990s.

Rust diseases can be identified by the galls’ shape and location and by cankers present on the trees. On jack pine seedlings and saplings, stalactiform stem rust can cause elongate swellings on branches or the main stem (trunk).

A jack pine with stalactiform stem rust galls that squirrels have chewed on

A jack pine with stalactiform stem rust galls that squirrels have chewed on.

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