PAW PAW, MI (WKZO AM/FM) — Last summer you may have seen trees covered in caterpillars, with their droppings falling from the canopy, and spongy brown egg masses on every surface
This has been a common sight throughout Michigan’s forests according to the Van Buren Conservation District in Paw Paw.
The culprit is now known as the Spongy Moth, or Lymantria dispar, and id was first introduced to North America in 1869. While it used to be called the gypsy moth, the Entomological Society of America (ESA) has stopped recognizing that name. They did this because it used a derogatory term for Romani
people.
Recently, the ESA approved the name “spongy moth”, based on the common name in French, spongieuse. The new name refers to its spongy egg masses.
Large outbreaks of spongy moths can eat all the leaves off a forest of oaks, which can be an alarming sight.
Luckily, this kind of damage is unlikely to kill an oak unless it is also experiencing other stress. But, once there are no more oak leaves left to eat, the caterpillars
may move on to pine trees, which can be killed by this damage.
Control of spongy moth in Michigan relies on a fungus and a virus that both infect the moths and kill them. These diseases work separately.
The fungus does best in wet conditions. The virus, on the other hand, does best when spongy moth populations are at their highest. With Spring
of 2021 being drier than usual, the spongy moth populations exploded with both the virus and the fungus being well established throughout Michigan.
Those concerned with spongy moth on their property can take steps.
Scraping the egg masses into a bucket of soapy water will kill them, and can make a real dent in their populations.
Pheromone traps will not control spongy moth populations because they only attract males.
Questions about spongy moth can be answered by contacting Michigan State University at https://www.canr.msu.edu/outreach/ask-an-expert
