Pest

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.

Rhizosphaera needlecast on balsam fir

Posted on by colleenrobinson
Rhizosphaera needlecast of fir produces rows of round black fruiting bodies on the needles. Photo by Colton Meinecke.

Rhizosphaera needlecast of fir produces rows of round black fruiting bodies on the needles. Photo by Colton Meinecke.

Rhizosphaera needlecast was found on balsam fir in Shawano County, with additional reports from Todd Lanigan (West Central WI) and Paul Cigan (Northwest WI). It causes chlorosis in the needles which drop off prematurely, giving the tree a thin appearance. This disease is related to the Rhizosphaera needlecast of spruce which you may be more familiar with. Literature indicates that it is most common on fir trees in shaded damp areas, or on trees that are under stress from other issues. You will see small black fruiting bodies on the undersides of the needles, although what really stands out is the thin foliage or off-color needles compared to other unaffected trees. 

Needles from the previous year have turned brown and will drop off prematurely due to Rhizosphaera needlecast.

Needles from the previous year have turned brown and will drop off prematurely due to Rhizosphaera needlecast.

Additional info can be found in this pest alert from the Forest Service.  

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

Sapsucker damage

Posted on by colleenrobinson
Supsuckers drill orderly holes through the bark into the cambium layer of the trees, causing them to bleed sap.

Sapsuckers drill orderly holes through the bark into the cambium layer of the trees, causing them to bleed sap.

Sapsuckers are birds that drill orderly holes through the bark of trees. The holes go just through the bark to the cambium layer, causing the tree to bleed. The sapsuckers then return to them later that day or the next day to feed on the sap. Sapsuckers are migratory and may just pass through an area in the spring, but they will sometimes return to the same tree over multiple years, creating new rows of holes each year. Trees will attempt to grow over this damage, and in most cases are successful. Occasionally the damage is so extensive that mortality can occur from that point up. Federal regulations don’t allow you to shoot sapsuckers, so control is usually some manner of deterrent, like wrapping the main stem with hardware cloth or burlap, or hanging scare tactics in the tree.

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

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

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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” →

Squirrel damage to spruce branch tips

Posted on by colleenrobinson
Spruce branch tips carpet the forest floor under a spruce tree. Squirrels will sometimes clip the ends of the branches off.

Spruce branch tips carpet the forest floor under a spruce tree. Squirrels will sometimes clip the ends of the branches off.

Have you ever found hundreds of green branch tips lying on the ground underneath or around a spruce tree? You’re probably observing squirrel damage. No one knows exactly why they do this although Shane Weber (former NOR Pest Specialist in Spooner) reported that he’s watched the little buggers clip and drop the tips of spruce branches without any apparent reason for doing so. There are also reports that they clip off the branch tips, nibble the new buds, and drop the remainder of the branch tip.

Michigan State University Extension has a document with photos of the squirrels eating the buds. I saw this damage near Woodruff this spring. Although it appears to be severe damage if you’re looking at the ground, when you look up at the trees you typically can’t see where any damage has occurred, so the health of the trees doesn’t appear to be compromised. 

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

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” →