Forest Health News

First Anniversary Of Spongy Moth’s Name Change

Spongy moth caterpillar

Spongy moth caterpillar. Photo credit: Jon Yuschock, Bugwood.org

March 2, 2023, marks one year since a new common name for Lymantria dispar, spongy moth, replaced the prior name of this insect, “gypsy moth.” This change was necessary because the word “gypsy” is an ethnic slur for the Romani people and the former common name equated people with insects. This is the first name change undertaken by ESA (Entomological Society of America)’s Better Common Names Project.

The current name—derived from the common name used in France and French-speaking Canada, “spongieuse“—refers to the moth’s sponge-like egg masses. Lymantria dispar is a damaging pest. This current name is a critical move in public awareness that focuses on an important feature of the moth’s biology while moving away from an outdated term. We encourage you to review any materials you may have on your website, ordinances and other material related to forest pests to ensure they are in accordance with this name change.

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Wisconsin DNR 2022 Forest Health Annual Report

By Becky Gray, Forest Health Team Leader, Rebecca.Gray@wisconsin.gov

The Wisconsin Department of Natural Resources’ Forest Health team recently completed the 2022 Forest Health Annual Report. The report summarizes impacts from pests, diseases and weather on the health of Wisconsin’s forests. Highlights from 2022 include:

  • Spongy moth’s rising numbers and evaluation of control techniques;
  • emerald ash borer continuing to spread and kill ash trees;
  • possible new biological control of buckthorn; and
  • drought and flooding impacts alongside insect infestations.

Read the report here.

2022 Forest Health Annual Report

Sign Up For Oak Wilt Vector Emergence Estimate Daily Email Notification

By Kyoko Scanlon, Forest Pathologist, Fitchburg, Kyoko.Scanlon@wisconsin.gov or 608-235-7532

Oak wilt is a serious disease that occurs when insects carrying oak wilt fungal spores land on a healthy oak tree’s fresh wound. To prevent oak wilt infections, it is important to avoid pruning, wounding and harvesting oaks when these insects are abundant, generally from April through July. Predicting exactly when these insects start to emerge in the spring can be difficult as their emergence is highly weather-dependent, and spring weather varies significantly from year to year.

In 2021, the Oak Wilt Vectors Emergence Thermal Model tool, a unique estimation tool, was developed as a collaborative project between the University of Wisconsin-Madison and the Wisconsin DNR to help with these predictions. This online tool offers localized recommendations about the emergence status of the two most important insects that transmit oak wilt in Wisconsin. The interface uses a degree-day model (Jagemann et al., 2018) constructed from insect trapping data and actual weather data, which helps refine the beginning of the periods when you should avoid pruning, wounding or harvesting oaks.

A screen shot of the oak wilt vector emergence homepage where the location and date data is entered to model growing degree days.

UW Extension’s Oak Wilt Vectors Emergence Thermal Model can help predict when oak wilt vectors may be coming. Photo Credit: UW Extension

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Make Plans To Control Spongy Moth Before The Eggs Hatch

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

Spongy moth (formerly known as gypsy moth) egg masses typically begin to hatch in April as temperatures warm. Each mass that hatches may produce up to 1,000 leaf-eating caterpillars.

Now is a great time to inspect your trees for egg masses and treat or remove any masses within reach. Wisconsin weather has been favorable for this pest over the last three years and populations have grown.

Photo of three spongy moth egg masses on the underside of a pine branch in Walworth County.

Three spongy moth egg masses on the underside of a pine branch in Walworth County. Photo: Bill McNee, Wisconsin DNR.

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Spongy Moth Management Webinar: March 8 at 6 p.m.

By Michael Hillstrom, Forest Health Specialist, Fitchburg, Michael.Hillstrom@wisconsin.gov

Spongy moth populations increased dramatically in 2022 and the outbreak is expected to continue in 2023.

Landowners interested in learning more about spongy moth management options are encouraged to attend an upcoming webinar hosted by UW Extension at 6 p.m. on March 8, 2023.

This is a free event, but registration is required. DNR Forest Health Specialist Mike Hillstrom and UW-Madison Insect Diagnostic Lab entomologist PJ Liesch will discuss a variety of effective management tactics for reducing spongy moth damage in varied settings from high value urban trees to forests.

A flyer for an upcoming webinar about spongy moth management that will take place virtually at 6pm on March 8, 2023.

UW Extension’s spongy moth management webinar can help you prepare to care for your land this spring.

Treat Your Valuable Ash Trees Against Emerald Ash Borer This Spring

By Bill McNee, Forest Health Specialist, Oshkosh, Bill.McNee@wisconsin.gov or 920-360-0942

Property owners with healthy, valuable ash trees are encouraged to treat them with insecticide this spring to protect against emerald ash borer (EAB). The pest is currently the most damaging threat to trees in Wisconsin, killing more than 99% of the ash trees it infests.

Woodpecker damage during the winter is often the first sign that an ash tree is infested. The birds remove pieces of bark while feeding on EAB larvae inside the tree. Insecticide treatment of infested ash trees is more likely to be successful if the trees have low or moderate levels of woodpecker damage.

Now is a good time to consider insecticide protection, because the treatments are typically done between mid-April and mid-May. Ash (in the genus Fraxinus) is the only type of tree that needs protection against EAB. Mountain ash and prickly ash do not need protection because the insect does not attack them.

Ash tree branch in West Allis has been damaged by woodpeckers. Sections of bark are missing, exposing the tree’s light brown wood.

This ash tree branch in West Allis has been damaged by woodpeckers feeding on EAB larvae beneath the bark.
Photo: Bill McNee, Wisconsin DNR.

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Make Your 2023 Spongy Moth Treatment Plans Early

By Bill McNee, DNR Forest Health Specialist, Oshkosh
bill.mcnee@wisconsin.gov or 920-360-0942

As long as weather conditions are favorable for the spongy moth* (formerly known as gypsy moth) population, the current outbreak is predicted to continue and spread to other parts of Wisconsin in 2023. Property owners are encouraged to examine susceptible host trees (including oak, birch, crabapple, aspen and willow) and plan ahead.

Spongy moth egg masses on a tree next to a penny for size comparison.

Spongy moth egg masses are tan-colored lumps that are larger than a penny, about the size of a nickel or quarter. Photo: Wisconsin DNR

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Harvest Timing Affected By Spongy Moth

By Bill McNee, DNR Forest Health Specialist, Oshkosh
bill.mcnee@wisconsin.gov or 920-360-0942

Numerous spongy moth egg masses on a bur oak in southern Waukesha County, November 2022.

Numerous spongy moth egg masses on a bur oak in southern Waukesha County, November 2022. Photo: Bill McNee, Wisconsin DNR.

Forest managers planning silvicultural treatments in spongy moth susceptible stands (containing a large proportion of host species including oak, birch, aspen and basswood) are encouraged to annually conduct egg mass surveys in the few years prior to the scheduled treatment to predict if heavy defoliation is likely. The results may indicate that management activities should be altered or delayed until an outbreak has ended. At present, stands that were heavily defoliated in 2022 or are predicted to be heavily defoliated in 2023 are most likely to need a management delay or alteration.

It is recommended that a time interval be left between a stress agent (such as heavy defoliation or significant drought) and stand thinning so that the trees can recover from pre-existing stress before being subjected to additional stress. One growing season is a common interval for healthy stands that are not being subjected to drought or other stresses. A longer interval is suggested if the tree stress has been more severe or if the stand was not healthy and vigorously growing at the time of defoliation. The same interval is probably appropriate regardless of which stress agent is the pre-existing one. A protective aerial spray may prevent tree stress from defoliation but is usually not economically viable due to the high cost of an aerial treatment.

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DATCP: Dead Spotted Lanternflies Detected On Nursery Stock From Out-of-State

On Nov. 3, 2022, the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) received a report of spotted lanternfly from a Walworth County landowner. The observant landowner had found multiple dead and a single dying adult spotted lanternfly on nursery stock purchased from an Illinois nursery. This serves as a reminder to always inspect your stock upon arrival in the nursery trade and prior to planting in your yard.

See the full article in DATCP’s What’s Growing On? November Newsletter.

Learn more about spotted lanternfly on DATCP’s website.

Spotted Lanternfly with wings outspread

Bur Oak Blight Confirmed In Fond du Lac County

By Bill McNee, DNR Forest Health Specialist, Oshkosh, bill.mcnee@wisconsin.gov

Recent lab examination has confirmed bur oak blight in Fond du Lac County. The disease affects only bur oaks and is caused by the fungus, Tubakia iowensis.

Map of Wisconsin counties where bur oak blight has been confirmed.

Map of counties where bur oak blight has been confirmed. Map credit: Wisconsin DNR.

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