Care for your woods

Insects and disease in storm-damaged trees

On July 19 & 20, two separate lines of severe thunderstorms swept across Wisconsin causing significant forest damage in numerous counties. Straight line winds in excess of 100 mph and 16 documented tornadoes caused extensive damage to trees including main stem breakage, branches and tops broken, tipping and root damage and complete uprooting of trees. After the storms passed, the first order of business was to check on people, clear and open roads and make sure damaged homes were secured. As those tasks were completed, thoughts then turned to the damaged forests.

Map of damage assessment across land ownership types. From 2019 storms in northern Wisconsin.

Coarse-scale damage assessment from recent storms in northern Wisconsin. Percent damage and number of acres affected were estimated during ground and aerial surveys.

Some insects and diseases can take advantage of storm-damaged trees and cause long-term damage to forest stands. Continue reading to learn more about these issues, how to deal with them and how to contact professionals who can help landowners make decisions about their land.

Aerial view of extensive damage to aspen stands. Landscape of trees leaning from high winds.

Aerial view of aspen trees leaning from high wind in storm event.

Pines are first priority

Storm-damaged pine stands should be a landowner’s top priority when deciding where to start. Salvaging pine is much more urgent than oak or other hardwood stands because damaged pines will quickly begin to stain, and insects and disease will rapidly infest the damaged trees.

Broken and leaning pine trees following storm event. Damaged trees are more vulnerable to bark beetle attack.

Bark beetles quickly attack leaning, broken or uprooted pines.

Native bark beetles such as red turpentine (Dendroctonus valens) and pine engraver (Ips pini) will rapidly attack damaged trees that are leaning, broken or uprooted as well as fresh logs in log decks. Bark beetles will continue to attack storm-damaged trees and can move on to attack healthy pine once their populations grow. For more info on bark beetles, check out the WI DNR bark beetle factsheet.

White-spotted sawyer (Monochamus scutellatus) is another native beetle that will move in when a pine tree is nearly dead (or freshly cut). If you’ve ever stood by a conifer log pile and heard scratchy chewing noises, you were listening to this native pine sawyer.

Armillaria is a fungus that attacks the roots of storm-damaged trees. Tree mortality from armillaria root disease won’t show up until 1-3 years after the storm.

The bottom line to minimize insect and disease issues is to harvest your pines as soon as possible after the storm. Check out this printer-friendly factsheet for more information about salvage harvests, pests and replanting in storm-damaged pine stands.

Heterobasidion root disease in pine and spruce

Heterobasidion root disease (HRD), previously known as annosum, is a serious fungal disease of conifers, particularly pine and spruce. Infected trees decline and eventually die. Infection occurs when a spore lands on a freshly cut stump and germinates. Once in a stand, the disease can move from an infected stump to nearby trees through root contact, eventually killing those neighboring trees.

If a pine or spruce stand is within 25 miles of a known HRD pocket and a harvest or salvage will be done, it is recommended to treat pine and spruce stumps with a preventative fungicide within 24 hours of the tree being cut. To find out if you’re within 25 miles of a known HRD pocket, check out the interactive HRD web map.

When salvaging storm-damaged trees, it may be difficult to quickly find a logger who is certified to apply pesticides or one who has the equipment to spray the stumps as they are being cut. It may also be impractical or impossible for logging equipment to cut and treat those trees that are down or broken. Although efforts should be made to arrange preventive stump treatment, under this type of emergency harvesting, treatment of stumps at the time of harvest may not be practical. Refer to the HRD guidelines and the modifications that reference salvage (Chapter 3, Modification 4, and Chapter 4, Modification 4). For more information about HRD, visit the DNR HRD webpage.

Hemlock borer

Hemlock borer (Melanophila fulvoguttata) is a flatheaded wood-boring beetle whose immature stage bores into stressed or recently killed hemlocks. Storm-damaged hemlocks provide a good breeding ground for hemlock borers, and their populations grow large enough that they attack living hemlocks. To avoid hemlock borer attack on living hemlocks, promptly salvage windblown hemlock following a storm event. If you must thin standing trees around living hemlocks, the intensity of thinning should be as light as possible.

Oaks and other hardwood stands

Distribution of oak wilt in Wisconsin showing sparse distribution in most northern counties.

Counties shown in red have oak wilt throughout the county, although it may not be in every stand. Oak wilt is not common in northern Wisconsin.

Don’t rush – deterioration of oak is not an immediate concern. A thoughtful approach to salvaging your oak stands will be more beneficial in the long term. Oaks with broken roots or major branch/stem breakage may be attacked by the native two-lined chestnut borer (Agrilus bilineatus). Larvae of this beetle bore under the bark of oaks and can girdle and kill branches or entire trees. Branch mortality or whole tree mortality due to this insect will show up 1-3 years after a major stress event like these storms.

 The good news is that the July 19 and 20 storms occurred after the high-risk period for new oak wilt infections. Oaks are highly susceptible to infection by the oak wilt fungus (Bretziella fagacearum) during spring and early summer (April 15 – July 15 in the north and April 1 – July 15 in southern Wisconsin). Oaks in the red oak group will be killed completely while just a branch may die on white and bur oaks.

If salvage of stands with oak will occur next spring during the high risk period, please see the oak wilt guidelines for information on harvesting to minimize introduction of oak wilt There is a guideline modification for salvage harvesting that you could consider, so check out the guidelines to decide what is best for your property. Read more about oak wilt on the DNR oak wilt webpage.

What to salvage

Uprooted trees, and those with completely broken tops, will die and should be salvaged. Standing trees with some broken branches are judgment calls. A general rule is to salvage the tree if more than 50% of the crown or top is broken, but there may be situations when these damaged trees could be left to help your forest recover. A professional forester can help you with these determinations. Trees that are leaning may have broken roots or broken stem fibers and should be considered for salvage. Check locally for wood disposal sites or refer to the DNR page on cleaning up storm debris.

Firewood

Storm-damaged trees can be utilized for firewood, but you should be careful not to move firewood long distances and risk introducing invasive species like emerald ash borer, gypsy moth and oak wilt to new areas. Instead, let the firewood age in place and burn it locally. For more information, visit the DNR firewood page. Always use proper protective equipment when operating a chainsaw.

Continued monitoring

Trees do not recover from stresses very quickly. Dieback, and even mortality associated with the storm, could continue for 2-3 years. Hail damage associated with the storms may not be apparent until next spring. You should continue to monitor your storm-damage stands for several years, especially if additional stresses occur in the year or years after the storm damage (such as a drought, defoliation, etc.). If you notice trees dying in the year following the storm or even two years after the storm, you should discuss this with your forester.

Replanting when do you start over?

If you have a pine stand that was salvaged and you plan to replant to pine on that site, wait!  Pales weevil (Hylobius pales) is a native insect that will infest freshly cut pine stumps. That alone is not a concern, but as new adults emerge from stumps, they must do a “maturation feeding” on conifer twigs, which can girdle them. If the only “twigs” available are the seedlings that you just planted then they will feed on those, possibly killing the seedling and causing extensive failure of your new planting. Wait for the second springtime following your salvage/harvest before you replant. Example: you salvaged your stand in August 2019, you should not replant until the spring of 2021. Another example: you salvage your stand in May 2020, you should not replant conifers on that site until spring of 2022.

Talk with a professional

If you’re still unsure of how to proceed with making decisions about the storm damage on your land, you should contact a professional forester or forest health specialist for insect and disease questions. You can also find lots of resources and information on recovery from the storm at the Wisconsin DNR storm damage page. Major storms like this can devastate a landscape and deal a crushing blow to the family forest. Discussing your options with a forester and creating a game plan that will benefit you and your land will start you on the road to forest recovery.

Aerial view of extensive storm damage surrounding a home in Wisconsin.

Storm damage was extensive in numerous counties. For scale, note the house near the center of this photo.

Flooding affects forest stands across state

By Mike Hillstrom, forest health specialist, Fitchburg, Michael.Hillstrom@wisconsin.gov, 608-513-7690

It’s another wet year in many parts of Wisconsin with water levels in lakes and rivers remaining very high. Seasonally wet areas are staying wet for longer, and areas that have not been wet for years are flooding or experiencing rising ground water levels. DNR forest health staff are increasingly noticing tree mortality due to these hydrologic issues. This occurs because flooding and high water reduces the amount of oxygen in the soil, depriving trees with submerged roots of the oxygen needed for growth and respiration. Along with submerged roots, trees can also die from uprooting and from subsequent insect and disease attack following flooding stress.

Trees being impacted by river flooding.

Trees being impacted by river flooding.

It may become necessary to conduct salvage harvests in flooded stands. Of course, the flooding also makes site access difficult. This is particularly concerning in stands where salvage harvests are needed to capture value, such as stands impacted by insects like emerald ash borer and eastern larch beetle.

Please let your local forest health specialist know if you are seeing flood-damaged stands. It is recommended to keep setting up salvage sales where appropriate. Access to wet or flooded sites can be difficult and may require frozen ground conditions if the site is expected to remain wet in the near-term.

Find your local forest health specialist on the DNR forest health webpage and learn more about flooding damage and mitigation with this resource from UW-Madison Division of Extension.

Professionally-designed HRD guidelines now available

Cover page of HRD guidelines documentThe professionally-designed version of the Heterobasidion root disease (HRD) stump treatment guidelines is now posted on the DNR’s HRD webpage. The revised stump treatment guidelines, developed to reduce the risk of introduction and spread of HRD in Wisconsin, were implemented January 1, 2019. The content is the same as the guidelines that were approved last year, but this document has a layout that is much more user-friendly. Explore the new look of the HRD guidelines.

 

Ants, aphids and sooty mold on white pine

Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665

Ants, aphids, and sooty mold can cause stunting and death of young white pines, but fortunately there are some steps you can take to protect your trees from these pests.

Ants guard aphids from predators as they feed. In exchange, the ants collect the sweet honeydew excreted by the aphids.

Ants (upper right) guard aphids from predators as they feed. In exchange, the ants collect the sweet honeydew excreted by the aphids.

Continue reading “Ants, aphids and sooty mold on white pine”

My Wisconsin Woods Values Your Woodlands

YOUR WOODS can be a source of food for your family.
OR your favorite hunting ground.
OR even create a source of income!

Whatever you value most, your woods are your gateway to the outdoors. Whether you own several hundred acres or just enough to take a short walk, sustainably managing your woodland is important. The best part is you don’t have to do it alone. My Wisconsin Woods, a public, private partnership serving woodland owners across the state, has launched a comprehensive landowner portal to connect you with natural resource professionals, forestry events in your area, and free information and materials. Recently released is a video series for landowners who are curious about what forestry benefits might exist or have nagging concerns. This series was made possible through the generous support of the Ruffed Grouse Society and David Moore with production and content provided by the Department of Natural Resources, Aldo Leopold Foundation and Driftless Area Land Conservancy.

So let’s go exploring …

May 18: WWOA Open Woods events across Wisconsin

Are you a woodland owner who would like to learn more about caring for your woodlands and keeping it healthy? Perhaps you are thinking of purchasing woodlands?  This day is for you!

YOU are invited to join Wisconsin Woodland Owners Association’s (WWOA) 40th year celebration of educating and assisting Wisconsin’s private woodland owners by attending one of their Open Woods events on Saturday, May 18, 2019. WWOA members around the state will celebrate by opening their private woodlands to the public and hosting a variety of family-friendly events to showcase how they have improved their land through forest management.

The list of event hosts and activities on the WWOA website continues to be updated, so check back often.​ Bring your family, friends, and neighbors to enjoy a walk in the woods or special activity.

Each site will offer a variety of fun events such as walks with the hosts and forester or other natural resource professionals to showcase how the woodlands have been cared for or tentative projects on the land. Other entertainment may include children’s activities with Smoky Bear, crafts, natural bird feeders, wildflower seed bombs, and tree/plant/wildlife identification and exhibits from various nonprofit organizations and agencies. Many locations are also offering snacks and refreshments or encouraging participants to bring a picnic lunch to enjoy in the woods.

Learn more about caring for your woods at www.wisconsinwoodlands.org

Invasive insects threaten Wisconsin hemlock

By Mike Hillstrom, forest health specialist, Fitchburg, Michael.Hillstrom@wisconsin.gov, 608-513-7690

Two invasive insects, hemlock woolly adelgid (HWA) and elongate hemlock scale (EHS), pose serious threats to Wisconsin’s hemlock trees. Although neither insect is established in Wisconsin, both insects have been found in recent years on infested nursery stock or live tree material that was shipped into the state. Fortunately, these introductions were detected and the plant material destroyed. But with HWA established in hemlock stands of several Michigan counties along Lake Michigan, natural spread to Wisconsin is anticipated.

Because of the risk, forest health staff from the Department of Natural Resources (DNR) and the Department of Agriculture, Trade and Consumer Protection (DATCP) are conducting surveys for early detection of these pests. Both pests could appear in many settings including urban and rural forests, yard trees and holiday tree plantations so everyone has a role to play in looking for these pests and reporting what they see.

HWA and EHS both feed on tree needles with sucking mouthparts. When populations are large enough, this feeding causes excessive fluid and nutrient loss, leading to declining tree health. Both insects can be found together on infested hemlock trees.

A group of adult hemlock woolly adelgid covered in white waxy filaments feeding on hemlock needles.

Characteristic white wax coating of adult hemlock woolly adelgid.

There are a few key ways to spot these insects. HWA is most obvious in winter when white, wax-covered adults are present. You may also see hemlock foliage turning gray-green in color as tree health declines. Adult EHS have a waxy cover and feed on the underside of hemlock, spruce and fir needles. Damage from EHS appears as yellow banding on needles. Crowns appear progressively thinner as infested needles die and fall off prematurely. Both insects also have tiny immature crawlers that may be seen moving on infested trees.

Tiny adult scales protected with a waxy cover feed on needles causing yellow banding.

Adult elongate hemlock scale and yellow needle banding (Credit: WI DATCP).

If you suspect you’ve found either HWA or EHS, please report it immediately to your local DNR forest health specialist. For more information about HWA, visit the DNR and DATCP webpages. To learn about EHS, visit the DATCP webpage.

Make trees mean more

Spring is upon us and that means the tree planting season is too. Trees are vital to our environments; they provide individuals and communities with clean air, clean water, reduced cooling costs, safer neighborhoods, and a place to play and gather. But trees provide much more than that, they can help show how much we care for others, a beautiful living reminder of the legacy of a person. Arbor Day is this month, and it is the perfect time to plant a tree and illustrate our feelings for others. Continue reading “Make trees mean more”

Protect oaks from oak wilt by waiting to prune

By Don Kissinger, urban forester, 715-348-5746, don.kissinger@wisconsin.gov and Paul Cigan, forest health specialist, 715-416-4920, paul.cigan@wisconsin.gov

To protect oak trees from the often-fatal oak wilt disease, don’t prune, cut or injure oak trees from April through July. 

Pruning and cutting oaks in spring and early summer leaves them vulnerable to oak wilt, which rapidly kills trees in the red oak group and weakens those in the white oak group. Any damage during this time, including broken branches caused by storms, exposes living tree tissue beneath the bark and provides an opportunity for the oak wilt fungus to infect the tree.

Sap-feeding beetles introduce the disease by carrying oak wilt spores from infected trees or firewood to fresh wounds. Healthy oaks can become infected in as little as 15 minutes after the creation of a wound. 

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

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

The trees most likely to die from oak wilt infection are in the red oak group, including northern pin oak, northern red oak, red oak and black oak. The white oak group is more likely to survive infection and includes bur oak, swamp white oak, white oak and English oak.

Tree paint or wound dressing is not normally recommended on pruned or wounded surfaces, but for damaged oaks an immediate light application of these products may be the only defense against oak wilt infection from April through July.

Pruning in spring can be damaging to any deciduous tree because their energy reserves are low as they produce new buds and leaves following the winter months. In general, the best time to prune is in winter when trees are dormant. 

As of January 31, oak wilt has been found in all Wisconsin counties except Ashland, Iron, Forest, Taylor, Door, Kewaunee, Calumet and Manitowoc counties. Several of these counties contain the highest abundance of healthy and productive oak forests in the state. Taking recommended precautions will help keep them that way for years to come.

Oak wilt and other diseases move easily on or in firewood logs year-round, so keeping firewood local, or purchasing Wisconsin-certified firewood, is another important component of protecting trees and keeping forests healthy. Visit the DNR firewood page for more information and a directory of certified firewood vendors.

More information, including a recently released oak wilt video, is available at the DNR oak wilt page. Additional information about proper pruning techniques is available from community foresters or through DNR resources such as this tree pruning poster

Don’t change EAB plans due to cold weather

By Bill McNee, forest health specialist, Oshkosh, bill.mcnee@wisconsin.gov, 920-360-0942

The recent frigid temperatures in late January and early February are likely to kill many overwintering emerald ash borer (EAB) larvae, but the tree-killing pest isn’t going away. The insulating properties of tree bark keep the larvae warmer than the outdoor air temperature, and wind chills do not affect the larvae because they are sheltered. The pest is also adapted to subzero temperatures based on its native range in eastern Asia where cold winters are common.

Prepupal larva seen during post-polar vortex sampling to assess larval mortality.

Overwintering prepupal larva, from February 2019 in Brookfield, WI.

On the morning of January 31, many parts of Wisconsin had low air temperatures between -30 and -35 degrees F. In places where it was this cold, scientific studies predict that most EAB larvae will be killed. Where low temperatures were between -20 and -30, larval mortality is likely to be lighter. Overwintering larvae were examined about 1 week after the cold snap in Brookfield (Waukesha County), where the low was -26, and few of the larvae were observed to have physical signs of freezing damage. Many of the larvae began moving within three days of being brought indoors. However, physical damage to the larvae may not yet be apparent, and normal-looking larvae may ultimately die from the cold temperatures.

Populations of the pest are likely to rebound, since each female beetle that emerges this summer will lay as many as 200 eggs. It is not currently known if larval mortality will significantly delay ash tree decline and mortality, although this may occur in areas that experienced the lowest temperatures. A cold spell in early 2014, that was not quite as cold, had no noticeable impacts on EAB spread or ash decline/mortality in areas known to be heavily infested.

The introduced biological controls of EAB, commonly known as “EAB wasps,” are at least as cold-tolerant as EAB. It is expected that these wasps will persist in and around release sites and continue parasitizing EAB eggs and larvae.

Forestry experts do not recommend changing EAB management plans solely due to the cold weather.

  • Continue to look for EAB in ash trees. Woodpecker damage is a good sign that an ash tree is infested with EAB or other pests.
  • Insecticide treatment of high-value ash trees near known infestations should be continued this spring.
  • Don’t delay tree removals or timber harvests that are already scheduled. Giving non-ash tree species more time to grow means that the future impacts of EAB will be reduced.
  • Continue planting non-ash tree species.
  • To help slow the spread of EAB, review firewood rules in Wisconsin. Buy firewood in the local area where you plan to burn it or buy Wisconsin-certified firewood that has been treated to eliminate pests. Certified firewood is often available at DNR-managed properties or you can buy from an independent certified firewood dealer.

Additional information about emerald ash borer, insecticide treatments and forest management can be found online at www.emeraldashborer.wi.gov.