Detect and Treat for Spongy Moth on Trees
What do you know about how to detect and treat for spongy moth on trees? We recently got an update on this invasive species and the damage it can do to trees in our area.
Every February the University of Wisconsin offers continuing education for professionals in the landscape industry. These short courses cover a variety of topics and keep new and experienced people in the landscaping industry aware of what’s up and coming. They also offer new takes on traditional practices. Ours is an industry that is always evolving with new technology and scientific advancements.
Resurgence of Spongy Moth
This week one of the big take-aways was the resurgence of Spongy Moth, formerly known as Gypsy Moth. This pest is known around the world for it’s spongy looking egg masses which resulted in its new nomenclature. It is not so much the moth that causes the problems, it’s the caterpillars which can defoliate an entire tree. Unfortunately, their favorite meals are some of our favorite trees. Oaks, lindens, birches, pine & spruce are all on the top of their list. If those aren’t available they will eat maple, elm, nut trees and many others.
Spongy Moth is Invasive Species
The moth was brought to the US in the late 1800’s and is therefore considered an invasive species. It unfortunately has very few predators here in the US, which has allowed its population to explode. Some biological controls have been effective but they are not practical for the home landscape. Blue Jays are one of our native birds that will eat the caterpillars, but most birds don’t enjoy them because they are covered with prickly hairs. Some rodents enjoy eating the pupal stage of the moth and chickadees will eat the egg masses, but none of these are enough to even put a dent in the problem.
How to Detect and Treat for Spongy Moth Egg Masses
So how can you help? At this time of year one of the easiest and most environmentally friendly ways is to go out and look at your trees; are there any brown, spongy patches on them? If yes, you will want to scrape them off if you can and let them soak in a bucket of soapy water to kill the eggs. Each of those masses can contain up to 1000 eggs. That is potentially 1000 caterpillars that would be infesting your trees. If they are too high or if scraping off egg masses is not your thing, they can be sprayed with Horticultural Oil before they hatch. This will smother the eggs, but you must soak the entire mass. This can be done by the homeowner or by a tree care professional.
Treatment Option for Spongy Moth Caterpillars
If you’ve missed the egg stage and find the caterpillars on your trees you can apply barrier methods or look into an insecticide spray. Be sure to only use a spray labeled to use for the Spongy Moth. Not all insecticides work on all insects so it’s important to make sure the chemical you are using will work on this pest. Always consult the label for the proper application or have a professional come and treat your trees.
We would like to acknowledge and thank PJ Liesch from the UW-Madison Insect diagnostic lab for providing us with an update on the status of this pest in our state. For more detailed information on the Spongy Moth and what you can do to help, head to the University of Wisconsin’s info page: https://fyi.extension.wisc.edu/spongymothinwisconsin/