Firewood

Dutch elm disease is prevalent this year

Posted on by Kirsten Held

Dutch elm disease seems to be quite prevalent around the state this year, including the northwoods.  Symptoms, including whole tree yellowing and wilting have been occurring this summer, and will continue into this fall.  Dutch elm disease is an exotic fungal disease that is spread by the elm bark beetle and can spread underground through root grafts as well.  Since bark beetles are generally not attracted to smaller trees (sapling to small pole size) people often get their hopes up that their small elms have “escaped” and will survive and grow to maturity.  Unfortunately, as soon as the trees are large enough for the bark beetles to be interested in them the trees may become infected with Dutch elm disease.  The first symptom you will see is usually a single branch on which the leaves turn yellow and die.  The rest of the tree will die shortly after that.  Elm trees attempt to fight the fungus by walling off the portion of the tree where the fungus is located but this can lead the tree to self-induced water deprivation and death.  More info on Dutch elm disease, including useful pictures, can be found in the U.S. Forest Service document How To Identify and Manage Dutch Elm Disease.

Dutch elm disease is spread by elm bark beetles, which create artistic galleries under the bark of the tree.

Dutch elm disease is spread by elm bark beetles, which create artistic galleries under the bark of the tree.

Chemical injections can protect single trees, and some communities in North America still have large stately elms due to this strategy.  For new plantings, there are some disease resistant cultivars (those crossed with other elm species) and some disease “tolerant” cultivars of American elm which tolerate the disease without completely killing themselves.

Written by: Linda Williams, forest health specialist, Woodruff, (Linda.Williams@wisconsin.gov), 715-356-5211 x232.

Oak wilt signs are showing up

Posted on by colleenrobinson
Oak leaves from an oak wilt infected tree. The outer portions of the leaf will be brown or have a water-soaked appearance. Part of the leaf remains green even though the leaf has dropped off the tree.

Oak leaves from an oak wilt infected tree. The outer portions of the leaf will be brown or have a water-soaked appearance. Part of the leaf remains green even though the leaf has dropped off the tree.

Trees that were infected with the oak wilt fungus this spring, (whether from overland spread by beetles or underground spread by connected root systems) are beginning to drop their leaves. Leaves can drop anytime between July and September. This wilting and dropping of the leaves happens fairly quickly, and trees can go from looking nice and healthy to having lost most of their leaves within just a few weeks. This year I saw my first wilting oaks on June 28, although in areas further south the leaf drop may have begun earlier. Oak wilt is a non-curable, fungal disease specific to oaks. Once the fungus infects a tree it will begin to spread outward from the roots of the infected tree through grafted roots and into the roots of neighboring oaks, eventually killing the neighboring oaks. In this way pockets of dead oak will be created as each year more oaks die. For more information on oak wilt biology, prevention, and control check out the WI DNR’s oak wilt page. 

Firewood from trees that have died from oak wilt will remain infectious for 1 full year (12 months) after the tree has died. There are many areas of northern Wisconsin where oak wilt is not common. Please do not move firewood long distances because you could move oak wilt into a new area.

Many northern counties don’t have oak wilt or have only a few known infections. This map shows townships in the north where oak wilt has been identified. In the red counties oak wilt is considered to be scattered throughout the county, although it will not be found in every stand.

Many northern counties don’t have oak wilt or have only a few known infections. This map shows townships in the north where oak wilt has been identified. In the red counties oak wilt is considered to be scattered throughout the county, although it will not be found in every stand.

Written by: Linda Williams, forest health specialist, Woodruff, (Linda.Williams@wisconsin.gov), 715-356-5211 x232.

Oak wilt identified near Sayner in Plum Lake Township, Vilas County

Posted on by colleenrobinson
Oak wilt fruiting body formed under the bark, shown here with the bark peeled away. The dark grey lump of stuff is the fruiting body which produces the spores.

Oak wilt fruiting body formed under the bark, shown here with the bark peeled away. The dark grey lump of stuff is the fruiting body which produces the spores.

I’ve identified oak wilt in Plum Lake Township, Vilas Co, west of Sayner. This is the first find of oak wilt in Plum Lake Township. The closest known oak wilt location is 6.7 miles from this new site. The tree rapidly dropped its leaves last July, and when it didn’t leaf out this spring the homeowner called me. Upon examining the tree I was able to find an oak wilt pressure pad, which is the fungal spore mat that forms under the bark and causes the bark to crack, which is how beetles can get access to the spores and move them to other oaks. 

Oak wilt is found throughout the counties shown in red. Where oak wilt is uncommon the townships where oak wilt has been identified are shaded in pink.

Oak wilt is found throughout the counties shown in red. Where oak wilt is uncommon the townships where oak wilt has been identified are shaded in pink.

The oak wilt map has been updated. Oak wilt is not common in our northern counties so the map highlights in pink the townships where oak wilt has been identified in the northern counties. The oak wilt guidelines for timber sales were updated about a year ago and list some exceptions and modifications for situations in which it is not necessary to implement the cutting restrictions during the high risk time period of the year (April 15 – July 15 in the north). 

Homeowners and those not doing timber sales should try to avoid pruning, wounding, or cutting oaks during the high risk time period of April 15 – July 15 in the north. This is the time of year when the beetles that can spread the spores overland will be attracted to fresh wounds on your trees; if you prune, wound, or cut your oaks during this period the beetles can introduce oak wilt to your tree. If it is necessary to prune, wound, or cut trees during that period, wound paint should be applied.

Oak wilt is always fatal to trees in the red oak group, which includes northern red oak, northern pin oak, and black oak. Trees that were infected with the oak wilt fungus this spring will begin rapidly dropping their leaves in July and August.

Written by: Linda Williams, forest health specialist, Woodruff, (Linda.Williams@wisconsin.gov), 715-356-5211 x232.

The Asian longhorned beetle battle continues in some states, and a new area is deregulated.

Posted on by colleenrobinson
Asian longhorned beetle is a large, glossy black beetle with white spots and white banding on its antennae.

Asian longhorned beetle is a large, glossy black beetle with white spots and white banding on its antennae. Photo by: Dennis Haugen on bugwood.org.

USDA APHIS continues to monitor and conduct control efforts in areas where Asian longhorned beetle is established. They recently released a statement that they were “removing 28 square miles from the Asian longhorned beetle (ALB) regulated area in the eastern part of Queens, New York”. Quarantines are usually lifted after surveys have not turned up new beetles or damage in the quarantine for a certain number of years. We do not have any infestations of Asian longhorned beetle in Wisconsin that we’re aware of, but it’s necessary to stay vigilant.

 

 

Continue reading “The Asian longhorned beetle battle continues in some states, and a new area is deregulated.” →

Invasive insects and disease awareness month

Posted on by colleenrobinson
Vin Vasive is the spokesman for invasive insects at USDA APHIS. He is made up of invasive species. This USDA APHIS poster was designed by Deb Levy Creative.

Vin Vasive is the spokesman for invasive insects at USDA APHIS. He is made up of invasive species. This USDA APHIS poster was designed by Deb Levy Creative.

April is invasive plant pest and disease awareness month, and May 21-27 is EAB awareness week.

It’s spring, and a good time to remember that invasive species can be easily moved long distances by unsuspecting citizens; maybe even you! All it takes to potentially start a new infestation is to move things we often like to take with us, but don’t know are a problem:

  • firewood,
  • infected or infested plant material,
  • an infected or infested piece of fruit, or
  • even a decorative piece of northwoods style furniture that hasn’t been properly treated to kill pests hiding inside.

Take a moment to think about whether you are unknowingly moving items that could harbor pests. The Hungry Pests website lists things you can do to prevent the spread of invasive species, whether you’re a birdwatcher, gardener, hunter, logger, or anyone. Check it out! While you’re there check out some short videos of their “spokesman” Vin Vasive, who has gotten much creepier over the years. 

Help spread the word

Coming up, May 21-27 is emerald ash borer awareness week, which is right before the Memorial Day holiday, when lots of travelling, camping, and opening up of summer cabins occurs. The Don’t Move Firewood website has a nice video of how to identify an EAB infested tree. More detailed videos are also available at dnr.wi.gov, keyword “forest health.” If you would like some examples of outreach tools or publications you can use to promote EAB awareness, check out the Don’t Move Firewood website; there you’ll find games for kids, an EAB craft project, videos, press releases, and news articles from past years. 

Written by: Linda Williams, forest health specialist, Green Bay, (Linda.Williams@wisconsin.gov), 920-662-5172. Categories: FH, UF. Tags: Statewide FH, Insect, Pest