Article by: Mike Hillstrom, Forest Health Specialist
In 2020, forest health staff in Wisconsin, Minnesota and Iowa received calls about black walnut stands being defoliated and webbed. In 2021, the defoliation expanded to multiple additional black walnut stands in southwest Wisconsin, while northeast Iowa and Minnesota continued to see damage. Recently, molecular work completed by the Wisconsin Department of Agriculture, Trade and Consumer Protection has identified the larvae causing the damage as a native Tortricid moth, Gretchena amatana.
G. amatana caterpillars on tree.
Fine webbing covers walnut tree trunk.
Continue reading “Mystery Walnut Defoliator Identified”
By Andrea Diss Torrance, Invasive Insects Program Coordinator, firstname.lastname@example.org, 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”
By Don Kissinger, DNR Urban Forester, 715-348-5746 or Don.Kissinger@wisconsin.gov; Paul Cigan, DNR Forest Health Specialist, 715-416-4920 or Paul.Cigan@wisconsin.gov
The Wisconsin Department of Natural Resources (DNR) urban and forest health specialists recommend not pruning or cutting oaks from April through July to protect oak trees from the often fatal oak wilt disease.
The spring season often draws property owners outdoors to soak up rays of long-awaited sunlight, breathe in some fresh air and begin seasonal yard maintenance and cleanup projects. While spring is a time to dust off yard tools like rakes, shovels and weed clippers, when it comes to the health of oak trees, keeping those chainsaws and trimming tools a safe distance away will go a long way to ensure that your trees stay healthy for many more spring seasons to come.
Sap-feeding beetle on a diseased oak tree in Sawyer County.
Continue reading “Protect Oak Trees From Oak Wilt By Pruning After July, Not Before”
Bill McNee, Forest Health Specialist, Oshkosh. Bill.Mcnee@wisconsin.gov or 920-360-0942
Property owners with healthy, valuable ash trees should consider treating 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. Now is an excellent time to consider insecticide protection because the treatments are typically done between mid-April and mid-May once leaves begin to return.
Treatments on already-infested ash trees are more likely to be successful if the trees have low or moderate levels of woodpecker damage.
This ash tree branch in West Allis has been attacked by woodpeckers looking for larvae to eat.
Continue reading “Treat Your Valuable Ash Trees Against Emerald Ash Borer”
By Bill McNee, DNR Forest Health Specialist, Oshkosh, Bill.Mcnee@wisconsin.gov or 920-360-0942
Typically, gypsy moth egg masses hatch in April as temperatures warm. Now is a great time to do an egg mass inspection to look for unknown infestations and treat or remove any masses within reach. Each mass can result in 500 to 1,000 leaf-eating caterpillars.
Egg masses are tan-colored lumps and vary from about the size of a nickel to a quarter. They can be found on many outdoor surfaces such as tree trunks, the undersides of branches, buildings, rocks, fences, retaining walls, firewood piles and picnic tables.
Gypsy moth egg masses on the underside of a maple branch.
Continue reading “Look For Gypsy Moth Egg Masses And Prepare For Hatch; DATCP Slow-The-Spread Treatments Announced”
By Kyoko Scanlon, Forest Pathologist, Kyoko.Scanlon@wisconsin.gov or 608-235-7532 and Elly Voigt, Forest Health Communications Specialist and Lab Technician, Eleanor.Voigt@wisconsin.gov
Oak wilt is a serious disease of oaks that spreads to new areas when insects carrying oak wilt fungal spores land on a fresh wound of a healthy oak tree. To prevent oak wilt infections, it is important to avoid pruning, wounding and harvesting of oaks when these insects are abundant.
Predicting when these insects emerge in spring can be difficult as their emergence is highly weather-dependent and spring weather varies significantly year to year. The good news is that a new online interface is now available to provide users with localized information about the emergence status of the two most important insects that transmit oak wilt in Wisconsin. Because the interface uses a degree-day model constructed from insect trapping data and actual weather data, it is useful to refine the beginning of the periods when pruning, wounding and harvesting of oaks should be avoided.
Continue reading “Oak Wilt Vectors Emergence User Interface Now Available”
By Elly Voigt, DNR Forest Health Lab Technician and Communications Specialist, Eleanor.Voigt@wisconsin.gov
The Wisconsin Department of Natural Resources (DNR) has just released several updated publications, including the annual update of the Heterobasidion root disease and oak wilt factsheets and guidelines. Updated versions can be found on the DNR’s forest health webpage by clicking the links below:
– Heterobasidion root disease factsheet
– Heterobasidion root disease guidelines
– Oak wilt factsheet
– Oak harvesting guidelines
Minor revisions were also made to the environmental cause of tree damage and conifer bark beetle factsheets. Visit the DNR webpage here for other forest health publications.
For more information on forest health, visit the DNR webpage, or talk to your regional Forest Health Specialist.
By Elly Voigt, DNR Forest Lab Technician and Communications Specialist, Eleanor.Voigt@wisconsin.gov
The Wisconsin Department of Natural Resources’ Forest Health team recently completed the 2020 Forest Health Annual Report. The report summarizes impacts from pests, diseases and weather on the health of Wisconsin’s forests. Highlights from 2020 include:
• An update on emerald ash borer in Wisconsin, including newly confirmed counties
• New township detections of oak wilt
• Flooding and tornado damage
• Summary of state nursery studies
For access to the report, visit the link here.
By Mike Hillstrom, DNR Forest Health Specialist, Fitchburg, Michael.Hillstrom@wisconsin.gov or 608-513-7690 and Brian Wahl, DNR Forestry Specialist, Fitchburg, Brian.Wahl@wisconsin.gov or 608-225-7943
During Wisconsin’s first week of 2021, a beautiful weather phenomenon occurred: rime ice. Rime ice forms when the tiny water droplets in fog freeze on trees and other objects. Hoarfrost, a similar phenomenon that occurs without fog, can form when water vapor in freezing air contacts a surface. The best news is that these winter conditions should not concern tree health when we emerge from the winter fog in spring.
Rime ice on a crabapple tree.
Continue reading “Learn More About Rime Ice And Winter Tree Damage”
By Elly Voigt, DNR Forest Health Communications Specialist and Linda Williams, DNR Forest Health Specialist, Linda.Williams@wisconsin.gov, 920-360-0665
The association between a tiny insect and an inconspicuous fungus is causing branch and sapling mortality. White pine bast scale (WPBS; Matsucoccus macrocicatrices) and Caliciopsis canker (caused by Caliciopsis spp.) are agents in an insect/disease complex impacting white pines (Figure 1).
Figure 1. Branch mortality caused by WPBS and Caliciopsis canker.
Continue reading “How to look for white pine bast scale and Caliciopsis canker”