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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.

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.

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.

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.

Giant hogweed (Heracleum mantegazzianum)

Posted on by colleenrobinson
Giant hogweed. Photo by Donna Ellis.

Giant hogweed. Photo by Donna Ellis.

Giant hogweed can be a threat to human health. Its sap has Furocoumarins (photosensitizing compounds) that can cause a skin reaction known as phyto-photodermatitis. This makes the skin highly sensitive to ultraviolet light. Swelling and blistering of the skin may lead to permanent scarring, and contact with the eyes can cause temporary and sometimes permanent blindness.

In Wisconsin, giant hogweed is classified as a prohibited species under the Invasive Species Rule (Wis. Adm. Code ch. NR 40). Its presence potentially causes economic or environmental harm or harm to human health. Isolated populations of Giant hogweed have been found in Wisconsin with immediate control taking place after verification.  Continue reading “Giant hogweed (Heracleum mantegazzianum)” →

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” →

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” →