Insect

Emerald ash borer new finds in Wisconsin

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.

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.

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

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”

Tamarack defoliation by larch casebearer

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

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

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.

Spiny oak sawfly

Spiny oak sawfly creates two types of defoliation. Young larvae chew holes in the leaves, and older larvae feed on leaf material between the veins. There are 3 sawflies near the center of this photo.

Spiny oak sawfly creates two types of defoliation. Young larvae chew holes in the leaves, and older larvae feed on leaf material between the veins. There are 3 sawflies near the center of this photo.

Spiny oak sawflies are one of the many things that will feed on oak leaves. Sawflies look like caterpillars but they aren’t, so the caterpillar-specific pesticide, Bt, will not be effective on them.  Spiny oak sawflies feed between the veins of the leaves, leaving a lacy appearance to the leaves.  They have forked spines all along their bodies which turn black as they get older. I’m not aware of this ever being much of a real problem but at one site in Price County the damage to understory oaks was significant.

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

Maple petiole borer causing leaf drop in northwest Wisconsin

Sugar maple leaf with black, shriveled petiole near leaf base, characteristic of maple petiole borer damage.

Maple petiole borer damage close up. Photo by Kyle Young.

Maple petiole borer has been active in the northwest. This exotic insect’s larvae cause tunneling damage to leaf petioles, leading to spring leaf drop in sugar maple. 

Landowners have reported leaves falling from their sugar maple for no apparent reason. While a first glance of the problem might look similar to maple anthracnose, which is a foliar disease that can also cause premature leaf drop in spring, and has also been notably active this year (see this month’s article on maple anthracnose), a closer inspection of characteristics on fallen leaves points to maple petiole borer instead. Continue reading “Maple petiole borer causing leaf drop in northwest Wisconsin”

Oak leaftier, oak leafroller, and eastern oak looper.

Oak leaftier rolls the leaf and secures it around itself with silk. Photo by Paul Veirauch.

Oak leaftier rolls the leaf and secures it around itself with silk. Photo by Paul Veirauch.

Localized oak defoliation near Pembine was the work of a combination of caterpillars. Oak leaftier, oak leafroller, and eastern oak looper were all found to be defoliating oak. Oak leaftier and oak leafroller can cause similar symptoms since both caterpillars purposefully roll the leaf around themselves. This trait makes it difficult to spray for them since the chemicals can’t directly reach them. When defoliation is moderate, no control is necessary. 

Oak leaftier and eastern oak looper on a ruler showing their size. Photo by Paul Veirauch.

Oak leaftier and eastern oak looper on a ruler showing their size. Photo by Paul Veirauch.

Additional information on these insects is available at these links:

http://www.forestpests.org/acrobat/oakleaf.pdf

http://www.sicktree.com/idotis/insects/lndloop.html

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