Gypsy Moth in Grand Rapids

JPEG image of Gypsy Moth caterpillar on a leaf

Gypsy moth has been a forest pest in Michigan for over 40 years. Over the last several years, the population and effects of gypsy moth have been higher in Grand Rapids than previous years. 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.


Overview

Our forestry team performed gypsy moth egg mass surveys and counts throughout Grand Rapids in the fall of 2018. We found gypsy moth populations above a threshold density of 1,000 egg masses per acre in several locations. These include Ken-O-Sha Park, Shangri-La neighborhood, Plaster Creek Trail, Covell Avenue, Ball Avenue and Woodlawn, Oakgrove and Oakhill Cemeteries. If you would like to see the egg mass density map, click here(PDF, 691KB) .

The gypsy moth population in Grand Rapids grew quickly because of dry spring seasons in 2016 and 2017. If conditions remain wet this spring, we expect the population to crash as a naturally occurring fungus that kills gypsy moth caterpillars known as Entomophaga Maimaiga, will likely spread among them. In addition, a virus called Nuclear Polyhedrosis Virus (NPV) naturally builds up in high density gypsy moth populations, causing populations to crash once they have reached high levels.

While relying on natural predators is recommended by experts, providing some control strategies on public and private properties for isolated populations can be effective. We're partnering with Friends of Grand Rapids Parks to train Neighborhood Forester volunteers. These training sessions will teach volunteers about gypsy moth egg mass scraping and how to apply tree bands to stop caterpillars from moving up the tree. We're also planning a spring application of Bacillus thuringiensis (Bt), a microbe found in soil that is toxic to the gypsy moth caterpillars.

2019 Spray Dates

Spraying occurred between May 31st and June 3rd, 2019.  Residents within and around the spray areas received a mailed notification before the spray date. Click below to see if your location was within the spray zone.  

Spray Areas Map


Information on the Day of the Spray

On the day of the spray, Hamilton Helicopters, Inc. applied a very fine mist of the bacterial agent Bacillus thuringiensis (B.t.), to cover the leaves of trees. The spray is a very common form of gypsy moth control. The spray will be difficult to see or feel and will dry in the tree canopy within a few hours.

After drying on the leaves, the spray will deplete the caterpillar population by infecting their stomachs after they eat sprayed foliage. The spray does not affect non-leaf eating insects, birds, fish or mammals.

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

Egg Mass Monitoring

Since we’ve been monitoring egg masses, we've found hatching eggs in the south side of Grand Rapids on May 7, 2019. 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. Gypsy 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.

PNG image of gypsy moth egg masses on a tree


Tree Bands

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.

Update Reports

Throughout the next months we will continue to monitor and track the gypsy moth population. Below are gypsy moth Updates: 

Steps You Can Take

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

  • Read the Homeowners Guide to Gypsy 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 gypsy moth to 311

Videos

Watch the following videos:

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