Statewide Forest Health

Oaks Hit Hard By Frost/Freeze Prior To Memorial Day

Written by: Linda Williams, DNR Forest Health Specialist, Woodruff, or 920-360-0665. 

A frost/freeze on the night of May 28 strongly impacted our oaks in areas of central and northern Wisconsin. Some leaves were completely killed while others had portions of the leaf that were impacted. Those leaves with some dead spots have continued to expand and grow but the dead parts of the leaf are causing them to curl and pucker. 

Oak leaves killed by the frost are brown, curled and puckered.

Oak leaves killed by the frost.

Continue reading “Oaks Hit Hard By Frost/Freeze Prior To Memorial Day”

Giant Hogweed: Rare But Harmful

By Bernie Williams, DNR Invasive Plant Specialist. or 608-444-6948. 

Giant hogweed is a non-native, invasive plant that has gradually gained a foothold in the northeastern U.S. Once popular for its massive size and white umbrella-like flowers, it was introduced as an ornamental as early as 1917. Now known for its harmful blisters, it is recognized as a public health hazard and controlled wherever possible.

Characteristic purple blotches and white hairs on green stem of giant hogweed. Photo credit: Herkulesstaude_Fritz Geller-Grimm

Continue reading “Giant Hogweed: Rare But Harmful”

Eau Claire And Richland Counties Now Added To The Gypsy Moth Quarantine

By Andrea Diss Torrance, Invasive Insects Program Coordinator,, 608-516-2223

Gypsy moth has moved slowly across Wisconsin in the last 30 years since gaining a foothold in the counties along Lake Michigan. This month, the Animal and Plant Health Inspection Service and the Department of Agriculture, Trade and Consumer Protection (DATCP) determined that the invasive pest has become established in Eau Claire and Richland counties and have extended the quarantined area to include them.  This is the first time since 2015 that new counties have been added to the quarantine. Fifty-two of Wisconsin’s 72 counties are now quarantined for gypsy moth.

Wisconsin Gypsy Moth Quarantined Counties

Continue reading “Eau Claire And Richland Counties Now Added To The Gypsy Moth Quarantine”

Oak Wilt Seasonal Harvesting Opportunities Web Map

By Paul Cigan, DNR Forest Health Specialist

The Forest Health Team has just launched an interactive web map showing areas where seasonal oak harvesting opportunities and restrictions exist within the state. The map provides users with general geographical information on the presence and seasonality of oak wilt restrictions to support decisions concerning the application of the Oak Harvesting Guidelines [PDF] during timber management planning and establishment. As a highlight, areas that favor flexibility in the application of the seasonal harvesting restrictions — based on the nearest known detection of oak wilt — are displayed on the map. If you have any questions about this map, please contact your regional Forest Health specialist.

Oak Wilt Seasonal Harvesting Opportunities Web Map

New Factsheets And Webpage Now Available

By Elly Voigt, DNR Forest Health Lab Technician.

The Wisconsin DNR’s Forest Health Team has recently released four new factsheets and a new webpage. The new factsheets are on the following topics:

Armillaria root disease

Beech bark disease

Peach bark beetle and cherry scallop shell moth

Hemlock woolly adelgid

Hemlock Woolly Adelgid Forest Health Factsheet

Continue reading “New Factsheets And Webpage Now Available”

Updated Emerald Ash Borer Treatment Guides Now Available

By Bill McNee, DNR Forest Health Specialist, Oshkosh. or 920-360-0942

The University of Wisconsin-Madison Extension has recently updated two insecticide guides for those interested in treating high-value ash trees against emerald ash borer (EAB). One guide lists options for homeowners and the other lists options for tree-care professionals. Download the guides here.

First page of the homeowner guide to EAB insecticide treatments.

First page of the homeowner guide to EAB insecticide treatments.

Continue reading “Updated Emerald Ash Borer Treatment Guides Now Available”

Keep An Eye Out For Beech Leaf Disease

By Elly Voigt, DNR Forest Health Lab Assistant, Fitchburg

Beech leaf disease (BLD) is a destructive disease affecting beech trees in the U.S. The disease has not yet been observed in Wisconsin, but it could become an issue in the future in the eastern third of the state, which is the edge of the American beech’s native range.

Figure 1. Symptomatic banding on beech foliage, as well as asymptomatic leaves. Photo: Ohio State University Extension

Continue reading “Keep An Eye Out For Beech Leaf Disease”

It’s Camping Season! Where Can I Get Firewood?

By Andrea Diss-Torrance, DNR Invasive Forest Insects Program Coordinator,, 608-516-2223

Most people know that using locally-sourced firewood helps prevent the spread of invasive pests and diseases. What may be less well known are the processes for finding local sources of firewood or learning where and how you can collect it yourself.

A set of images showing an oak wilt spore pad, an emerald ash borer beetle emerging from a tree and a gypsy moth caterpillar on a leaf.

In Wisconsin, oak wilt, emerald ash borer, gypsy moth and several other invasive pests and diseases are moved in or on firewood. During the camping season, these pests can emerge from transported wood to attack trees at the camper’s destination. Photo credit: Wisconsin DNR, MJ Raupp Bugwood, WDNR

Continue reading “It’s Camping Season! Where Can I Get Firewood?”

White Silk Tents In Trees

By Todd Lanigan, DNR Forest Health Specialist, Eau Claire. or 715-210-0150

Eastern tent caterpillars (ETC) are hatching and beginning to feed on host trees, including cherry, apple and crabapple. Landowners and homeowners may notice the white silken tents forming in branch forks which are spun by ETC.

A group of eastern tent caterpillars on a white silk tent on black cherry branches.

Eastern tent caterpillars on a black cherry tree. Photo credit: Wisconsin DNR

Continue reading “White Silk Tents In Trees”

The Tick App: ‘Your On-the-Go Tick Expert’

By Danielle Smith, Midwest Center of Excellence for Vector-Borne Disease, UW-Madison

Researchers at the University of Wisconsin-Madison, Columbia University and Michigan State University have developed the TickApp, a mobile smartphone application that allows users to learn how they can protect themselves, their families and their pets from ticks—and join a team of citizen scientists helping researchers better understand ticks and tick-borne disease risk.

Adult blacklegged tick on a dead leaf.

Adult blacklegged tick

Continue reading “The Tick App: ‘Your On-the-Go Tick Expert’”