Insect

Spiny oak sawfly

Posted on by colleenrobinson
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

Posted on by colleenrobinson
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.

Posted on by colleenrobinson
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.

Oak vein pocket gall

Posted on by colleenrobinson
Oak Vein Pocket Gall is characterized by lumpy bumpy veins on the back of oak leaves and is caused by the feeding of tiny gall midge larvae. Photo by Brenda Nordin.

Oak Vein Pocket Gall is characterized by lumpy bumpy veins on the back of oak leaves and is caused by the feeding of tiny gall midge larvae. Photo by Brenda Nordin.

The photo here shows oak vein pocket gall. This gall is caused by a tiny gall midge (fly) and causes the distortions that you see. It’s not really a problem for the tree, doesn’t cause premature defoliation, and won’t kill the leaves, but it will cause the leaves to be a bit gnarled for the remainder of the growing season. I’ve had a couple reports of this from Shawano and Brown Counties this summer so far. More info can be found on the Kansas State Research and Extension website.

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

Spruce budworm defoliation showing up

Posted on by colleenrobinson
The two center balsam fir are severely defoliated by spruce budworm while the outer two trees are less severely defoliated.

The two center balsam fir are severely defoliated by spruce budworm while the outer two trees are less severely defoliated.

Spruce budworm defoliation is starting to show up in the northern counties as the clipped foliage stuck in the caterpillar webbing turns rusty red. Defoliation this year may be reduced in some areas if the caterpillars were damaged by the multiple storms we’ve had this spring. Let us know where you’re seeing defoliation. The caterpillars should be pupating soon and moths will emerge a couple weeks after pupation. Spruce and balsam fir are defoliated by this pest, which is a native insect with periodic outbreaks. 

Outbreaks occur every 30-50 years, and last for 10 years on average. Our previous outbreak ran from 1970-1980. Mature balsam fir and spruce are preferred hosts, although younger balsam or spruce can be defoliated as well. Repeated defoliation can cause top-kill and eventually whole tree mortality. Balsam fir stands, or stands with a heavy component of balsam fir, are often more severely impacted, but don’t let that fool you into thinking it won’t defoliate pure spruce stands.  Continue reading “Spruce budworm defoliation showing up” →

Prepare now – gypsy moth caterpillars return

Posted on by colleenrobinson
Gypsy moth caterpillar with distinctive blue and red dots

Gypsy moth caterpillar with distinctive blue and red dots

This June, gypsy moth populations may rise to damaging levels in parts of Wisconsin. High numbers of gypsy moth caterpillars are a tremendous nuisance and can strip trees of their leaves. Combined with other stresses, such as drought or attacks by additional tree pests, this may kill the tree. The insect’s favorite food is oak leaves, but it will feed on many other tree species such as aspen, birch, crabapple and willow. You can take action to reduce the number of caterpillars that will feed on your trees, including placing sticky barrier bands on the susceptible tree species. Continue reading “Prepare now – gypsy moth caterpillars return” →

Oak wilt and hickory mortality Forest Health Fact Sheets are available

Posted on by colleenrobinson

The forest health program is in the process of updating some of our publications as Forest Health Fact Sheets. These publications offer biology, impact, prevention and management information about specific threats to forest health. Our new oak wilt fact sheet and hickory dieback and mortality fact sheet are currently available on the DNR’s forest health oak wilt and bark beetle webpages and will be available in the DNR’s online publications catalog  in the near future. Enjoy!

Written by: Mike Hillstrom, forest health specialist, Wisconsin Dells (Michael.Hillstrom@Wisconsin.gov), 715-459-1371.

Emerald ash borer new locations in Wisconsin

Posted on by colleenrobinson
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.

Emerald ash borer (Agrilus planipennis) 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.

If you know you have EAB, please contact us with that information so we can verify the infestation and update the maps. If your area:

  • is not shaded in green on the map please contact DNR or
  • is not shaded at all on the map please contact DATCP.

You can reach both agencies from the menu options when you call 1-800-462-2803.

New county quarantines

  • none

New finds in counties already quarantined

  • Brown County — village of Bellevue
  • Door County — village of Egg Harbor
  • Fond du Lac County — village of Rosendale and town of Springvale
  • Vernon County — town of Franklin

Written by: Linda Williams, forest health specialist, Green Bay, (Linda.Williams@wisconsin.gov), 920-662-5172.

Forest tent caterpillar update

Posted on by colleenrobinson
Forest tent caterpillars do not make web nests but may congregate and rest in groups on the bark.

Forest tent caterpillars do not make web nests but may congregate and rest in groups on the bark.

Caterpillars hatch from the eggs of a forest tent caterpillar egg mass.

Caterpillars hatch from the eggs of a forest tent caterpillar egg mass.

Forest tent caterpillars are hatching. Egg mass surveys were conducted in Iron, Ashland, Bayfield, Sawyer, Polk, Washburn, Douglas and Burnett counties, and no egg masses were observed. Surveys in Vilas, Oneida and Forest counties found very few egg masses.

Based on this information we expect low numbers and minimal defoliation again this year, but please let us know if you see forested areas with more significant defoliation.

Written by: Linda Williams, forest health specialist, Green Bay, (Linda.Williams@wisconsin.gov), 920-662-5172.