With this spring’s dry weather in Wisconsin came predictions of the largest spongy moth population in years.
When spongy moth populations are high, we often see heavy mortality of the larger caterpillars due to two pathogens. Heavy caterpillar mortality will reduce the severity of the following year’s outbreak and often causes a population crash during the current year. If a heavy die-off of caterpillars is observed, please let your local DNR Forest Health Specialist know about it.
Three spongy moth egg masses on a branch in Walworth County. Photo Credit: Bill McNee, Wisconsin DNR
Now that spongy moth* (formerly known as gypsy moth) egg laying is complete for 2022, it’s a good time to look for and dispose of egg masses produced by adult moths over the past two months.
Spongy moth egg masses are tan-colored lumps about the size of a nickel or quarter, and are found on trees, buildings and other outdoor objects. They may also be found in protected places such as firewood piles and birdhouses. Newly produced egg masses will feel firm and appear darker in color than older egg masses, which appear faded, feel spongy and do not contain viable eggs. The current-year egg masses will not hatch until next spring.
In 2022, Wisconsin’s spongy moth population grew for a third consecutive summer due to favorable weather conditions and limited caterpillar mortality from diseases. The outbreak was most dramatic in opposite ends of the state. In southern and southeast Wisconsin, several thousand oak-dominated acres were heavily defoliated and very large numbers of property owner reports were received by DNR staff. In Bayfield County, about 80,000 acres of rural defoliation was reported from aspen-dominated forests. Smaller patches of defoliation were also reported from several other counties.Continue reading “Look For Spongy Moth Egg Masses – Larger Outbreak Possible in 2023” →
The spruce budworm outbreak continues this year, but the amount of visible defoliation is generally lower than last year. Some areas of the Northwoods have severe defoliation this year, but in many other areas, the amount of new, green foliage far exceeds the amount of defoliation.
In areas where the defoliation appears less severe, you can still find plenty of caterpillars, but the new foliage is less eaten than anticipated. The late spring frost/freeze may have killed some caterpillars, or the long cool spring may have delayed bud-break enough that the caterpillars did most of their feeding on older foliage before the new foliage expanded.
The spruce budworm outbreak in Wisconsin started in 2012, and outbreaks typically last about 10 years. Mortality of balsam fir trees started to show up last year following several years of significant defoliation. Even with new growth on the trees this year, they may continue to decline, and mortality could still occur.
Defoliation is still present, but there is lots of new growth on balsam fir this year in many areas of northern Wisconsin.
Pine bark adelgids are tiny insects that suck the sap of white pines. Once they insert their mouthparts into the tree, they won’t move any more during their lifetime, so for protection, they grow a white, woolly covering around themselves. A young, white pine plantation in Vilas County is suffering severely stunted needles from the 2020 growing season due to very high populations of pine bark adelgid.
All branch tips on this white pine sapling have needles that were stunted by heavy populations of pine bark adelgid.
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.
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.
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.
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.
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: