Spongy Moth in Grand Rapids

JPEG image of Spongy Moth caterpillar on a leaf

Spongy moth (formerly known as "gypsy moth") has been a forest pest in Michigan for over 40 years. Over the last several years, the population and effects of spongy moth have been above average in Grand Rapids. This has mainly affected areas with high oak tree populations. Below, we've explained the situation, our plan of action, and what you can do to help


2022 Aerial Spray

Spray Dates: TBD. Estimated to happen late May to early June.

The City of Grand Rapids is contracting Hamilton Helicopters, Inc. to perform spongy moth aerial treatments in late May to early June in areas with the highest spongy moth populations. These spaces have experienced defoliation and have continuous forested land.

The exact day and time of the spray will be determined by weather, including rain and wind conditions. Additional details regarding the spray will be announced here and on the parks and recreation Facebook page. Residents living directly next to spray areas will receive a mailed notification.

View a Map of the Treatment Areas

On the day of the spray Hamilton Helicopters, Inc. will apply a very fine mist of the bacterial agent Bacillus thuringiensis (B.t.), covering the tree’s leaves.  The spray will be difficult to see or feel and will dry in the canopy within a few hours. The spray will affect caterpillars by destroying their stomachs after they eat sprayed foliage. It does not affect non-leaf eating insects, birds, fish or mammals. Spraying is wind and weather dependent and will likely take place during the morning. 

Below are several documents that further explain spongy moth and its treatment:

We’ve been monitoring spongy moth egg hatch and found eggs began hatching throughout Grand Rapids during the second week of May, 2022.

We expect it will take at least two weeks for all eggs to hatch. Once eggs hatch, caterpillars may remain on the masses several days before dispersing. Spongy moth caterpillars disperse by ballooning - sending out a silken thread and then carried by a breeze. It may take several days for caterpillars to find a suitable host.

Just after caterpillars have hatched, when they are small and young, barrier bands will prevent them from climbing back into trees after ballooning or when they have fallen. Barrier bands can be made using duct tape and/or a waterproof, sticky material such as the Tanglefoot or petroleum jelly.

When the bark is dry, wrap duct tape around the tree, shiny side out, pressing the tape firmly into the bark cracks to prevent caterpillars from slipping under the bands. Then, turn the tape over and wrap once more with the sticky side up. The tape should be wrapped a few inches wide and placed around the tree trunk at chest height – about four feet above the ground. If possible, spread additional sticky Tanglefoot or vasoline onto the lower portion of the barrier.

Throughout the next months we will continue to monitor and track the spongy moth population. Below are our previous Spongy Moth Updates:

Steps You Can Take

If you encounter a tree affected by spongy moth, there are a few things you can do to help.

  • Read the Homeowners Guide to Spongy Moth Management(PDF, 1MB) tip sheet
  • Water the tree(s) throughout the summer to help with leaf regrowth
  • Remove egg masses and wrap trees with a barrier
  • Treat the tree(s) with an insecticide like B.t. caterpillar and webworm control
  • Contact a local forester for treatment options. Foresters can be found at the International Society of Arborculture's website
  • Report sightings of spongy moth to 311

Scrape Egg Masses

October through late April

City Forester points to a group of spongy moth egg masses on the trunk of a tree  A close-up image of a spongy moth egg mass

Look for egg masses on tree trunks and scrape them into a cup of soapy water using a plastic putty knife or other dull scraping tool. Egg masses are light brown, sponge-like in appearance and about the size of a quarter.

Watch a how-to video


Apply Tree Bands

Late April through Late May

PNG image of a tap band around a tree to prevent gypsy moth caterpillars from moving up the tree

Just after caterpillars have hatched, when they are small and young, barrier bands will prevent them from climbing back into trees after ballooning or when they have fallen.

HOW TO MAKE YOUR OWN TREE BAND 

Barrier bands can be made using duct tape and/or a waterproof, sticky material such as Tanglefoot insect barrier or petroleum jelly.

  • When the bark is dry, wrap duct tape around the tree, shiny side out, pressing the tape firmly into the bark cracks to prevent caterpillars from slipping under the bands
  • Turn the tape over and wrap once more with the sticky side up. The tape should be wrapped a few inches wide and placed around the tree trunk at chest height (about four feet) above the ground
  • If possible, spread additional sticky Tanglefoot or vasoline onto the lower portion of the barrier.

Watch a how-to video


Videos

Watch the following videos: