Three spongy moth egg masses are found on a tree branch at Kettle Moraine State Forest Southern Unit in Walworth County. / Photo Credit: Bill McNee, Wisconsin DNR
Now that spongy moth egg laying is complete for 2023, it’s a good time to look for and dispose of the 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 can be found on trees, buildings and other outdoor objects. They may also be found in protected places such as firewood piles and birdhouses.
Emerald ash borer was detected in Rusk County in northwest Wisconsin in late July, making it the 69th of Wisconsin’s 72 counties that have confirmed presence of the invasive insect. / Photo Credit: Paul Cigan, Wisconsin DNR
The emerald ash borer (EAB) has been detected for the first time in Rusk County, making it the 69th of Wisconsin’s 72 counties to determine the presence of the invasive insect.
On July 25, Wisconsin Department of Natural Resources Forest Health staff investigated a report of several ash trees with woodpecker flecking and branch dieback in a village park along Railroad Avenue in the Village of Sheldon.
In many areas across Wisconsin, conditions were right for the worst outbreak of spongy moth caterpillars (Lymantria dispar) in more than a decade.
The caterpillars of this invasive insect — formerly known as gypsy moth — prefer to feed on oak, birch, crabapple, aspen and willow leaves, but will also feed on many other tree and shrub species. As of early August, caterpillars have pupated, but adult moths remain present.
A green maple leaf found on the ground with a broken petiole (leafstalk) due to damage by the maple petiole borer. / Photo Credit: Wisconsin DNR.
Some sugar maple trees in the northern half of Wisconsin experienced leaves dropping to the ground this spring.
These leaves were green and had no apparent areas of damage, but they covered the ground under some trees. A closer look showed these leaves had short petioles (leafstalks) that had been broken off when they fell, which indicates a tiny sawfly larva called maple petiole borer was to blame.
Examples of white “wool” coating on trees heavily infested with beech scale at Kohler-Andrae State Park (left) and in the Town of Beecher in Marinette County (right). / Photo Credit: Bill McNee (left) and Linda Williams (right), Wisconsin DNR.
Fourteen years after first detecting beech scale (Cryptococcus fagisuga, a non-native insect) in Door County, sites with high populations of beech scale have been found in additional counties. Beech scale is believed to have spread through the range of American beech in Wisconsin’s eastern counties, but until now has only been seen at low levels outside of Door County.
A dead terminal leader, resulting from an attack by white pine weevil. Photo: Linda Williams, Wisconsin DNR.
White pine weevil (Pissodes strobi) is a native insect that can kill the terminal leader of white pine, jack pine and spruce. Wisconsinites often refer to this insect as Tip Weevil.
The insects prefer to attack stout terminal leaders. When the terminal leader dies, lateral branches grow upward and compete to take over apical dominance. This can leave a noticeable crook for decades. If two or more lateral branches take over, forking can occur. New terminal leaders may be attacked in subsequent years, causing more crook or forking.
Spruce and jack pine tend to recover better from weevil damage than white pine because the lateral branch that takes over apical dominance often creates a less prominent crook.
Umbel of a giant hogweed plant. This invasive plant can grow stems 2-4 inches in diameter and can grow as tall as 15 feet. Photo: USDA APHIS PPQ, Oxford, North Carolina; Bugwood.org
This time of year, calls start rolling in about potential sightings of the invasive plant giant hogweed (Heracleum mantegazzianum). Although occurrences of the plant remain rare in Wisconsin, from late May through early July giant hogweed is often confused with a native plant, cow parsnip (Heracleum maximum).
Both are large plants with similar habitat preferences. They prefer shady areas and are often found along stream banks, roadsides and ditches. Giant hogweed is a prohibited species under Wisconsin’s Invasive Species Rule NR40. Its fast growth rate crowds out native vegetation and erodes soil, and skin contact can potentially cause irritation.
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.
The statewide quarantine for emerald ash borer will end July 1, as one of several permanent rule changes proposed by the Wisconsin Department of Agriculture, Trade and Consumer Protection.
Changes are coming to some of Wisconsin’s rules for plant inspection and plant control, following legislative approval of a proposal from the Department of Agriculture, Trade and Consumer Protection (DATCP).