Forest Health News

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.

Emerald ash borer new finds in Wisconsin

Posted on by colleenrobinson
EAB peak emergence map. Tan color is approaching peak emergence, light green is peak emergence, and dark green is past peak EAB emergence. Map from June 19, 2017.

EAB peak emergence map. Tan color is approaching peak emergence, light green is peak emergence, and dark green is past peak EAB emergence. Map from June 19, 2017.

Initial emergence of Emerald ash borer (Agrilus planipennis) has begun in Wisconsin and is likely occurring throughout Wisconsin at this time. Peak emergence is approaching.

EAB continues to be found in new areas. Wisconsin continues to track EAB at the municipality or township level; quarantine counties are shown in tan and infested areas are shown in green on the map below.

New county quarantines

  • none

New finds in counties already quarantined

  • Columbia County — cities of Columbus and Lodi
  • Dane County — villages of Dane, Waunakee, and Windsor; cities of Fitchburg, Monona, and Sun Prairie; towns of Blooming Grove, Dane and Westport
  • Dodge County — city of Horicon
  • La Crosse County — town of Washington
  • Manitowoc County — town of Cooperstown
  • Sheboygan County — village of Elkhart Lake
  • Trempealeau County — village of Trempealeau
EAB quarantine map. Counties shaded in tan are quarantined for EAB, and include much of the southern half of Wisconsin, as well as other counties. Areas shaded in green are the townships and municipalities where EAB has actually been identified, and shows that not all counties that are quarantined are fully infested.

EAB quarantine map. Counties shaded in tan are quarantined for EAB, green areas are townships and municipalities where EAB has actually been identified.

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.” →

Large gypsy moth caterpillars now present; mating disruption treatments begin.

Posted on by colleenrobinson
Mature gypsy moth caterpillar with distinctive blue and red dots.

Mature gypsy moth caterpillar with distinctive blue and red dots.

By late June, gypsy moth caterpillars will be large (>1” in length) and noticeable in most of Wisconsin. Nuisance caterpillar problems and defoliation from the caterpillars will be apparent by now, even in the far northern counties. As of mid-June, we have only had a few reports of nuisance caterpillars. This is a hopeful sign that populations will remain low in 2018. The June rainstorms will also help the Entomophaga fungus to kill gypsy moth caterpillars.

Continue reading “Large gypsy moth caterpillars now present; mating disruption treatments begin.” →

Storm damage in May and June

Posted on by colleenrobinson
Young trees and branches that are whipped by strong winds may have splitting bark on their branches or trunks. Although the trees will eventually grow over these wounds, the wounds will dry out and probably open up a bit more.

Young trees whipped by winds may have splitting bark on their branches or trunks. The trees will eventually grow over these, but first the wounds will dry out and open up a bit more.

Storms, storms, and more storms! It seems like we’ve had a lot of storms that brought severe weather this year. Storm damage to oaks at this time of year creates the risk of oak wilt introduction in new areas as the beetles that can spread oak wilt are attracted to the fresh wounds from the storm damage. Pine that is damaged by the storm can be infested by bark beetles, or blue stain can enter the wood via hail wounds, or Diplodia can kill branches that were damaged by wind or hail. When blowdown or tornado damage occurs it presents some additional forest health concerns with staining and decay. We have some information available online regarding storm damage, which currently highlights the May 16 tornado but applies to all tornado/wind damage to your trees.

Some of the storms during the past month are highlighted below.
Continue reading “Storm damage in May and June” →

Oak damage from late frost, and ash dropping leaflets

Posted on by colleenrobinson
Northern red oak leaves severely distorted due to frost damage.

Northern red oak leaves severely distorted due to frost damage.

A late frost severely impacted newly emerging oak leaves in many northeast Wisconsin counties including Brown, Outagamie, Oconto, and Shawano. Due to the development stage, oaks were the most heavily impacted compared to other species, and oaks in the open were more severely impacted than oaks in forests. Many oaks in open areas had to send out additional leaves, which were then tattered by strong storms that pelted them with heavy rain, hail, and strong winds. Oak leaves in the counties mentioned may look a little rough for the remainder of this year. 

The late frost also contributed to damage on ash leaflets, which, in addition to early anthracnose infections on the leaflets has caused ash in some northeastern counties to drop their damaged leaflets, leaving them mostly bare. They will send out additional leaves to get them through the summer. 

 

 

Northern red oak leaves tree severely defoliated due to a late frost event. Photo taken May 29, 2017 (same tree as other pics in this article).

Northern red oak leaves tree severely defoliated due to a late frost event. Photo taken May 29, 2017 (same tree as other pics in this article).

Northern red oak sending out new leaves due to severe defoliation from a late frost event. Photo taken June 2, 2017 (same tree as other pics in this article).

Northern red oak sending out new leaves due to severe defoliation from a late frost event. Photo taken June 2, 2017 (same tree as other pics in this article).

Northern red oak leaves refoliating following a severe frost event. Photo taken June 7, 2017 (same tree as other pics in this article).

Northern red oak leaves refoliating following a severe frost event. Photo taken June 7, 2017 (same tree as other pics in this article).

Ash leaflets damaged by anthracnose may be dropped by the tree.

Ash leaflets damaged by anthracnose may be dropped by the tree.

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

Tornado whips across northwest Wisconsin at unprecedented scale

Posted on by colleenrobinson
Approximate storm path and forest damage area.

Tornado path map. Map by Paul Cigan & Benjaman Garret.

An EF3 tornado swept through northwest Wisconsin from southeast Polk County to southwest Price County on May 16, leveling many structures and whole forest stands, in what the National Weather Service has declared the longest tornado path on state record. Continue reading “Tornado whips across northwest Wisconsin at unprecedented scale” →

Deciduous tree leaf loss

Posted on by colleenrobinson
Black, dead areas of leaf tissue on maple leaves caused by anthracnose.

Anthracnose on maple leaves. Photo by Joleen Stinson.

As anticipated, anthracnose is common on a number of deciduous tree species statewide this spring, especially maple and ash. Many of the maple samples we’ve seen also have tar spot. The cool, wet, humid conditions this spring were ideal for fungal leaf diseases. Anthracnose symptoms appear as patches of brown or black, dead leaf tissue which may cause leaves to curl or shrivel up as damage progresses. Trees may drop the infected leaves but will send out new leaves within a few weeks.

An aspen tree with less than half the leaves it should have because frost damage.

Aspen with thin crowns caused by frost damage. Photo by Bob DeBruyckere.

Damage to other species, including aspen, cottonwood and willow appears to have been caused by frost damage. These tree species likely became active and had the buds swell during the early warm up in February, then suffered damage to the buds and twigs from the cold weather thereafter. Although the damage was severe in some cases it seems that the trees produced new buds and are working on sending out additional leaves.

Significant dieback was noted in many locations around the state, including on some hybrid poplar in Shawano County, on trembling aspen in central and northern Oconto County, and on big toothed aspen in western Vilas County. We had reports of impacted aspen, cottonwood and willow from south central, southwest, central, west central and northcentral Wisconsin. Forest health specialists in Minnesota report similar damage.

Keep impacted trees healthy by watering (where possible) during hot and dry periods to help the trees recover.

Written by: Mike Hillstrom, forest health specialist, Fitchburg, (Michael.Hillstrom@wisconsin.gov), 608-513-7690

Tamarack defoliation by larch casebearer

Posted on by colleenrobinson
A patch of brown tamarack trees defoliated by larch casebearer caterpillars photographed during aerial survey in early June.

Larch casebearer defoliation visible from an aerial survey on June 7, 2017. Photo by Josh Haberstroh.

Tamarack defoliation by larch casebearer is evident in northcentral and northeastern Wisconsin again in 2017. The most severe defoliation occurred in Lincoln and Langlade counties, while more moderate defoliation was noted in Waupaca, Shawano and Oneida counties. I saw extensive damage in northern Wisconsin by this insect in 2014 but damage was much more localized and less severe in 2015 and no damage was documented in 2016.

Larch casebearer, Coleophora laricella, overwinters as young caterpillars and is able to start feeding as soon as the weather warms up in the spring. The caterpillars mine out the needles of tamarack causing them to turn brown by late spring. Tamarack trees will typically produce new needles after moderate or severe damage. Caterpillars pupate on the tree in early summer and moths mate and lay eggs in summer. A second round of feeding, which causes additional stress to the trees, occurs by young larvae in summer before they overwinter. Repeated defoliation can weaken the tree, making it more susceptible to mortality from eastern larch beetle.

Written by: Mike Hillstrom, forest health specialist, Fitchburg, (Michael.Hillstrom@wisconsin.gov), 608-513-7690

Periodical cicadas emerging early

Posted on by colleenrobinson
An annual or “Dog Day” cicada.

An annual or “Dog Day” cicada.

A recent article from Science Alert reported that some of the 17-year periodical cicadas associated with Brood X, have begun emerging – 4 years early! Brood X doesn’t typically emerge in Wisconsin, although it does emerge in some areas of Michigan and Illinois. The brood that emerges in a few areas of Wisconsin is Brood XIII which isn’t due to emerge again until 2024. We also have annual or “Dog Day” cicadas that emerge every summer in Wisconsin.

Cicadas are harmless, they do not bite or sting or attack people, they are not poisonous and don’t transmit disease, but they are big and the periodical cicadas emerge in huge numbers which can be quite upsetting to some people.

The problem for trees comes when the females lay their eggs. They use a stout ovipositor to puncture the twigs of small trees and shrubs, laying an egg in the slit created by the ovipositor. This damage to the tree can cause twigs to die and break off. Some young trees can be badly damaged and may lose most of their twigs and branches, they may die or be severely stunted.

An additional aggravation for many people is the very loud buzzing noise made by the males; some people refer to these insects as heat-bugs because their loud buzzing is often heard during the hottest days of the summer. 

Cicadas emerge from the ground, climb an object, emerge from their exoskeleton, and leave the empty exoskeleton behind after they expand their wings and fly off.

Cicadas emerge from the ground, climb an object, emerge from their exoskeleton, and leave the empty exoskeleton behind after they expand their wings and fly off.

For more info on periodical cicadas check out the Cicada Mania webpage.

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