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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.

Yellowheaded spruce sawfly

Posted on by colleenrobinson
There are 2 young yellowheaded spruce sawfly in this photo. As they get older they develop an orangish head capsule.

There are 2 young yellowheaded spruce sawfly in this photo. As they get older they develop an orangish head capsule.

Has anyone started to see defoliation from Yellowheaded Spruce Sawfly? This small sawfly seems to defoliate spruce without anyone noticing until it’s all done. We saw significant defoliation in 2015 (Door, Marinette, and Vilas counties) and 2016 (Outagamie, Shawano, and Waupaca counties) and if the population is going to remain high this year you should start seeing the defoliation soon. There is one generation per year and they typically feed on new expanding foliage from late May to early July. They will feed on all spruce (white, blue, Norway). The larvae blend in well with the needles so you’ll have to look closely as they can be difficult to spot.

If you have had defoliation in previous years from Yellowheaded Spruce sawfly you should monitor your spruce to determine if spraying will be necessary this year. Repeated severe defoliation can cause tree mortality.  More info can be found in this Forest Service publication.

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

White pine blister rust infections

Posted on by colleenrobinson
Spore-producing structure formed on edge of white pine blister rust canker in spring.

White pine blister rust fruit body.

White pine blister rust (Cronartium ribicola; WPBR), a naturalized pine rust disease, has been infecting white pine saplings in several northwest Wisconsin counties this spring. Although WPBR is common in the Lake States and can in some cases cause significant losses in white pine, taking several steps can help prevent infections before they start and manage them before damage occurs.

Like many foliar diseases, WPBR infections are promoted by moist and cool spring weather that results in persistent wetness on foliage; specifically, at least 2 days of wetness while air temperatures are under 68oF. Maintaining dense stocking (6×6) reduces incidence of infection by increasing the mortality of lower branches, most susceptible to infection. Similarly, successive pruning of lower branches beginning at age 5 to a minimum branch height of 9 ft. prevents leaf contact with moist surface vegetation and can increase airflow, hastening foliar drying. If caught early enough, infections can be stopped before reaching the main stem by pruning out flagging twigs and branches to at least 4 inches past the interior-most wilting needles; if the main stem is closer than 4 inches from the interior-most canker or wilted foliage, unmanageable stem infection may already have occurred and the tree cannot be saved. 

White pine sapling with significant blister rust infection causing resinous, sunken canker, and main stem girdling.

White pine sapling infected with blister rust. Photo by Kyle Young.

Written by Paul Cigan, forest health specialist, Hayward (Paul.Cigan@Wisconsin.gov), 715-416-4920.