Spongy Moths

Adult spongy moth

Spongy moths are an invasive pest species in Washington. As caterpillars, they can eat hundreds of different types of plants and trees. They lack native predators and diseases, so their populations can increase quickly if they are not controlled. The Washington State Department of Agriculture (WSDA) has a monitoring and eradication program to keep spongy moths from establishing a permanent breeding population in Washington.

How are spongy moths controlled?

Washington State uses an integrated pest management approach to control spongy moths. This includes:

  • Extensive monitoring with pheromone traps.
  • Visual inspection for egg masses to determine where a breeding population is located.
  • Manual destruction of egg masses.
  • Targeted control for caterpillars with least toxic methods effective for the site. Btk is the most commonly used product for spongy moth control in Washington.
  • Follow-up trapping to evaluate success of eradication.

What is Btk?

Btk, or Bacillus thuringiensis kurstaki, is a naturally occurring bacteria found in soil. It is a commercially produced pesticide and sprayed on tree and plant foliage to control caterpillars.

When caterpillars eat sprayed leaves, they stop eating and die. The product is specific to caterpillars and has been shown to have little toxicity to mammals, birds, fish, or insects such as honeybees, beetles, and spiders. Btk is extensively used in organic agriculture and is available in home gardening products. The Foray 48B product used by WSDA for spongy moth control is certified for use in organic agriculture.

Spongy moth caterpillar

What other ingredients are in Foray 48B?

Foray 48B also contains water, residues of food crops that are used to grow the Btk, and food additives. The additives are approved for use in food by the US Food & Drug Administration (FDA) and are found naturally in foods or made for use in food products. Most people already encounter these additives in beverages, foods, and cosmetics. Washington State Department of Health (DOH) toxicologists have reviewed the ingredients in Foray 48B and conclude that the product poses very low concern for health.

People with serious allergies to food or preservatives should minimize contact with the spray by following our advice below. According to the company that makes Foray 48B, (Valent BioSciences) there is no wheat or gluten in the product.

What are the human health concerns of Btk?

Btk isn't considered toxic for people. It doesn't harm water supplies. Btk isn't considered a human pathogen. Human infections of Btk have been looked for but not seen in several large studies of people who lived in sprayed areas.

Many years of experience with Btk products have shown that the vast majority of people living in sprayed areas report no symptoms. A small number of people have reported symptoms including skin rash, irritation of the eyes, nose, and throat, and worsening of asthma or allergies after spraying. It isn't clear whether Btk was responsible for the symptoms or if the symptoms were related to disturbed dust and pollens or another component of the spray.

Public Health Recommendations

Even though Btk has an excellent safety record, as a precaution, the DOH recommends that people in the spray area minimize their exposure by following these steps:

  • Remain indoors for at least 30 minutes after the spraying. It's a good idea to keep pets inside too.
  • Children should wait until moisture from the spray has dried on grass and shrubs before playing outside and should wash their hands after playing outside. Gardeners should follow the same precautions.
  • If you come into contact with the wet spray, wash the affected skin with soap and water. If wet materials get into the eyes, flush them with water for 15 minutes.

People who are more susceptible to infections or respiratory irritation should pay particular attention to these precautions. This includes people with an underlying illness such as leukemia, AIDS, or other immune system deficiency, people receiving radiation or chemotherapy treatment, and people with asthma, emphysema, or allergic sensitivities. People with concerns related to exposure to Btk, their health, or their immune system should contact their health care provider.

More Information

Spongy Moth, WSDA - Learn more about spongy moth biology, trapping, and when and where control efforts are planned.

Spongy Moth Name Change, Entomological Society of America - Learn why the name "gypsy moth" was replaced by "spongy moth."


Content Source: Pesticide Program