The pesticide used by the Washington state Department of Agriculture to fight invasive gypsy moths is a naturally occurring bacteria.
Bacillus thuringiensis kurstaki (Btk) commonly grows in soils and on plants worldwide and is toxic only to some insects, including caterpillars.
According to the state Department of Health, Btk is not toxic to humans and does not harm water supplies.
“This year, there were going to be residential areas that were going to get treating and we wanted to pick a product that was as safe as possible,” Department of Agriculture spokesman Hector Castro said. The department has used Btk for many years.
The inactive pesticide, which is organic, is applied to plants by air during the spring, when caterpillars hatch and start eating plants, the Department of Agriculture said. When consumed by caterpillars, the bacteria activates in their digestive systems, killing them within hours.
The Department of Health has guidelines to minimize exposure to the pesticide:
▪ Humans and pets should remain indoors for at least 30 minutes after the pesticide is sprayed.
▪ Wait until the spray has dried before playing or working outside, and wash hands when done.
▪ If contact is made, wash the affected area with soap and water; if it enters the eyes, flush them with water for 15 minutes.
Don’t worry about your gardens or fruit trees: Btk is considered safe for same-day consumption because of its low toxicity, Castro said.
The Department of Agriculture sent postcards to residents and businesses in affected areas to tell them about the impending spraying, Castro said. The state maintains a website at agr.wa.gov/gypsymoth where residents and business owners can sign up for phone calls, text messages or emails notifying of impending spraying.