Spongy Moth

moth on a tree

Spongy Moth

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.

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Signs of Spongy Moth Damage

Early Signs 

  • Control for small caterpillars (first and second instar stages) begins with Bacillus thuringiensis (Bt) application.
  • Bt is highly selective for caterpillars present at the time and has no effects on people, animals, birds, or non-lepidoptera insects.

Late Signs 

  • As caterpillars get large, Bt becomes ineffective, and contact insecticides are used until pupation.
  • Trees weakened by heavy defoliation from gypsy moth caterpillars may become susceptible to drought, disease, or other insect attacks, especially if they are already in poor health.

For Homeowners

To effectively control spongy moth infestation and protect your trees, it is important to aim for at least 85% leaf coverage. In some cases, this may require two spray treatments. The key is to target the caterpillar population while they are small and easier to control, minimizing the extent of feeding damage to your trees. To ensure the most suitable control strategies, it is recommended to consult with Certified Arborists at Wachtel Tree Science. They possess the expertise to assess your specific control needs and recommend appropriate methods based on sound scientific principles. Rest assured that the recommended control materials will prioritize environmental friendliness.

For Professionals

Spongy moth management involves a comprehensive approach that combines various control tactics and emphasizes the control of egg masses and caterpillar stages. It is important to note that the pupa and adult stages do not cause any feeding damage. To achieve effective control, professionals should prioritize reducing the caterpillar population early in their lifecycle when they are small and relatively easy to manage. The ultimate goal is to minimize feeding damage to trees and maintain a leaf coverage of 85% or better. When assisting homeowners with spongy moth control, Certified Arborists at Wachtel Tree Science should employ control methods backed by solid scientific evidence and choose environmentally friendly materials whenever possible.

Spongy Moth 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 a certified arborist from Wachtel Tree Science can help assess the threat spongy moths pose to your trees

Spongy Moth FAQs

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.