Pest

Emerald ash borer new finds in Wisconsin

Posted on June 28, 2017 by colleenrobinson

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.

Posted on June 28, 2017 by colleenrobinson

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 June 28, 2017 by colleenrobinson

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.” →

Tamarack defoliation by larch casebearer

Posted on June 28, 2017 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 June 28, 2017 by colleenrobinson

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.

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 June 28, 2017 by colleenrobinson

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 June 28, 2017 by colleenrobinson

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.

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 June 28, 2017 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 June 28, 2017June 28, 2017 by colleenrobinson

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.

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 June 28, 2017 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.

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.