Forest Health News

Tree mortality continues in flooded forests

Mike Hillstrom, forest health specialist, Fitchburg, Michael.Hillstrom@wisconsin.gov, 608-513-7690

Wisconsin has had historically wet weather the last five years, and the impacts to trees are escalating. Forest health staff have noted significant mortality of trees along lakes and rivers from rising water levels. Trees growing in low areas that have not flooded in many years are also being impacted.

Photo of flooded lakeside forest and dead trees around margin of lake.

Rising lake water levels causing conifer mortality.

Continue reading “Tree mortality continues in flooded forests”

Summary of spring 2020 balsam fir mortality event

Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665

The sudden balsam fir mortality event in Wisconsin in 2020 was similar to the spring 2018 mortality event, although the mortality this year was more scattered, and fewer trees were killed.

A balsam fir tree with a dead crown that has retained its needles.

Trees that died suddenly this spring retained their needles, which turned reddish-brown to brown.

Continue reading “Summary of spring 2020 balsam fir mortality event”

New emerald ash borer county detections: an update from DATCP and DNR

The Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP), in partnership with the Wisconsin DNR, has detected emerald ash borer in four new counties (Dunn, Oconto, Pepin and Shawano). Please read this DATCP article for more information.

Adult emerald ash borer beetle.

Adult emerald ash borer beetle.

If you are a landowner and have questions about ash trees in your woodlot, contact your local DNR forester using the Forestry Assistance Locator.  

Gypsy moth populations rebound in 2020 – look for egg masses this fall

By Bill McNee, forest health specialist, Oshkosh, bill.mcnee@wisconsin.gov, 920-360-0942

The summer of 2020 saw a major rebound of the gypsy moth population after several years of weather conditions that were unfavorable for the non-native, defoliating pest. A mild winter and average summer temperatures/precipitation during the caterpillar stage were all favorable for a population increase.

Gypsy moth egg masses are tan-colored lumps about the size of a nickel or quarter.

Female moth laying eggs on tree trunk.

Continue reading “Gypsy moth populations rebound in 2020 – look for egg masses this fall”

Oak webworms, blotchminers, skeletonizers and dead branch tips in late summer

By Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665

If you’ve ever looked closely at oak leaves in late summer you know that you can find lots of interesting things on them this time of year. You’ll see anything from a variety of caterpillars and galls of all shapes and sizes to dead portions of branches caused by insects and diseases. These late season defoliators rarely cause actual health issues for the tree, and rarely require any control, but they can be very noticeable with some dramatic damage. Continue reading “Oak webworms, blotchminers, skeletonizers and dead branch tips in late summer”

Green-striped mapleworm in northern Wisconsin

By Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665

Green-striped mapleworm caterpillars feed gregariously, so where you see one, you’re bound to see more. Their preferred hosts are red and sugar maple, but they can feed on oak and beech as well, especially if those species are mixed in with maples. As they feed, they leave behind only the main veins of the leaves. The adult moth is the lovely rosy maple moth.

Green-striped mapleworm caterpillar clinging to the underside of a maple leaf.

Green-striped mapleworm caterpillar.

Continue reading “Green-striped mapleworm in northern Wisconsin”

Spruce budworm and balsam fir mortality in northern Wisconsin

By Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665 

Spruce budworm defoliation was severe in many areas of northern Wisconsin this year. New needles on balsam fir and spruce were eaten, although in most areas the balsam fir had greater amounts of defoliation than the spruce. Feeding by this native caterpillar for several years in a row can cause trees to start to decline and even die, which is occurring in a number of areas of northern Wisconsin.

Mortality of balsam fir due to repeated defoliation by spruce budworm. Green trees in this photo, including hardwoods and pines, are not fed upon by spruce budworm.

Mortality of balsam fir due to repeated defoliation by spruce budworm. Green trees in this photo, including hardwoods and pines, are not fed upon by spruce budworm.

Continue reading “Spruce budworm and balsam fir mortality in northern Wisconsin”

Redheaded pine sawfly reported in northern Wisconsin

By Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665 

For the second year in a row, colonies of redheaded pine sawfly have been reported on understory red pine in northern Wisconsin, with the most reports coming from Vilas County. Redheaded pine sawfly was also noted in Portage County in central Wisconsin this year.

Redheaded pine sawfly larvae feed as a group, as shown in this photo where many sawflies are clustered on a single twig.

Redheaded pine sawfly larvae feed as a group.

Continue reading “Redheaded pine sawfly reported in northern Wisconsin”

Jack pine budworm defoliation seen in Juneau County

By Todd Lanigan, forest health specialist, Eau Claire, todd.lanigan@wisconsin.gov, 715-210-0150

Jack pine budworm, a native defoliator of jack pine and other conifers, caused defoliation of jack pine in the Town of Clearfield, Juneau County. Defoliation levels ranged from light to moderate, with some areas along roadways having higher levels of defoliation.

Jack pine trees defoliated by jack pine budworm.

Jack pine trees defoliated by jack pine budworm.

Continue reading “Jack pine budworm defoliation seen in Juneau County”

Wondering about large yellow wasps?

If you’ve noticed large yellow wasps flying around this summer, you may be wondering whether you’ve seen the Asian giant hornet (aka “murder hornet”). This probably gave you some pause considering all the headlines they received earlier this year,  but fortunately for Wisconsin and much of the Midwest, murder hornets have not yet been found in the region.

Close-up photo of cicada killer.

The cicada killer is a common native insect in the Midwest.

Continue reading “Wondering about large yellow wasps?”