What Is the Spongy Moth?
The spongy moth is an invasive insect that feeds on trees and shrubs. At times, many areas will continue to have outbreaks of spongy moths. As spongy moth populations reach outbreak levels, the necessity for control increases to reduce potential damage. Elimination of spongy moth from an area is not possible, even with controls. However, the reduction of the population is possible to a level where the stress on trees and people are tolerable.
Signs of Spongy Moth Damage
Early Signs
Small Caterpillar Control
Control for small caterpillars (first and second instar stages) begins with Bacillus thuringiensis (Bt) application.
Safe Treatment
Bt is highly selective for caterpillars present at the time and has no effects on people, animals, birds, or non-lepidoptera insects.
Late Signs
Contact Insecticides
As caterpillars get large, Bt becomes ineffective, and contact insecticides are used until pupation.
Susceptible Trees
Trees weakened by heavy defoliation from spongy moth caterpillars may become susceptible to drought, disease, or other insect attacks, especially if they are already in poor health.
Spongy Moth Prevention
For Homeowners
- Aim for at least 85% leaf coverage; this may require two spray treatments.
- Target the caterpillar population while they are small and easier to control, minimizing the extent of feeding damage to your trees.
- Consult with the ISA Certified Arborists at Wachtel Tree Science to ensure the most suitable control strategies.
For Professionals
- Provide a comprehensive treatment approach that combines various control tactics and emphasizes the control of egg masses and caterpillar stages.
- Prioritize reducing the caterpillar population early in their lifecycle when they are small and relatively easy to manage.
- Minimize feeding damage to trees and maintain a leaf coverage of 85% or better.
Spongy Moth Infestation Treatment
Step 1
Early intervention: Apply Bt to areas where caterpillars are present, as it selectively targets them without harming people, animals, birds, or non-Lepidoptera insects.
Step 2
Transition to contact insecticides: Use contact insecticides until pupation to disrupt molting for the first through third instar stages.
Step 3
Maintain tree health: Consulting an ISA Certified Arborist from Wachtel Tree Science can help asses the threat spongy moths pose to your trees.
Spongy Moth FAQ
Find answers to your questions about the spongy moth.
Will spongy moth feeding kill my trees?
No, not immediately. The tree, if healthy, will be ok. Trees with pre-existing conditions would be more susceptible to damage. Trees that have multiple years of defoliation are at risk as well.
Will treating my tree get rid of spongy moth?
No, the caterpillars will still be present since they can migrate in from other areas. Treatments are designed to limit the amount of feeding on the trees.
Why are some years worse than others regarding spongy moth infestations?
Populations will rise and fall largely based on weather conditions. Certain periods of dry weather allow the population to build.
What can I do as a homeowner to help limit feeding?
In addition to treatment, you can utilize tree bands as another way to protect your tree. Tree bands work by preventing the spongy moth caterpillars from climbing the trunk of your trees and therefore reducing feeding activity. The best timeframe to use tree bands is in late May or June.