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Btk Insecticide FAQs

Questions and Answers about Gypsy Moth Spraying and Your Health

What is Btk?
Bacillus thuringiensis kurstaki (Btk) is a bacteria found in soil in the natural environment. When moth larvae eat Btk it kills them.
There are many strains of Bt, several of which are used as biological pesticides on edible crops, including organically grown foods. The level of damage that a pesticide can cause is known as toxicity. The toxicity of the different Bt strains is insect specific. For example Bacillus thuringiensis kurstaki (Btk) is poisonous to moth larvae whereas Bacillus thuringiensis israelensis is poisonous to fly larvae.
The larval stage of insect life is most susceptible to Bt toxicity due to the active feeding behavior of larvae. The toxic “action” of Btk is activated by the larvae’s alkaline/basic stomach conditions. When gypsy moth larvae eat plants treated with Btk, a toxin is released in their stomach. This toxin infects and starves the insect. In contrast, human stomachs are acidic and when people eat crops treated with Btk, the toxins are not activated and harm does not result.

What is Foray® 48B?
Foray® 48B is a pesticide product that contains 12.65% Btk as its active ingredient.
Foray® 48B (EPA Registration No. 73049-427) is certified by the Organic Materials Review Institute (OMRI) as an organic product. In addition to the bacterial ingredient, Foray® 48B contains “inert or other" ingredients. The EPA assesses the toxicity of "inert or other" ingredients. Please refer to the US EPA website on Pesticide Inert Ingredients for more information. Foray® 48B is considered a low-risk pesticide product by the US EPA.

What are Gypsy Moths?
Gypsy moths are an insect pest that in their larval stage, as caterpillars, can defoliate (eat leaves off of trees).
 In other parts of the country gypsy moths have eaten thousands of acres of forests, orchards and landscapes. Gypsy moths are mainly a threat to plant life and habitat. When the number of the caterpillars in a location is very high, some people may experience allergic reactions. The gypsy moth caterpillars have spiny hairs which may cause welts or rashes, lasting up to 4-5 days. Population levels of gypsy moths in isolated infestations, such as those we have in Oregon, do not normally pose any health risks

How might I be exposed to Btk?
People are exposed to Btk through contact with soil in the natural environment or through their diet, at very low levels.
If you eat fresh fruits or vegetables, you probably have already ingested this bacterium. It is commonly sprayed on commercial and organic food crops. Exposure can also happen if you breathe it in or get it in your eyes. You may also be exposed if you ate or smoked after handling an object that’s been sprayed with a Btk product, and didn’t wash your hands.

Can Btk make people sick?
It is unlikely that indirect exposure to Btk will result in adverse health effects in people considering the widespread use of Btk in food crops and in insect control.
The toxicity of Btk has been researched in laboratory studies with animals and by monitoring people for more than 25 years. Btk is low in toxicity for humans and other mammals. People working in occupational settings, and people directly exposed to Btk, for long periods of time have a greater chance of reporting health effects. In occupational settings, people directly exposed for long periods of time have had mild skin irritation or short term breathing problems.
Reports of harmful effects from Btk or applications of Btk-containing products include:
  1. A corneal ulcer developed after a farmer splashed Btk into his eye. This healed after medical treatment.
  2. Rabbits given droplets of various strains of Bt in their eyes experienced temporary eye irritation.
  3. Participants in a community survey done before and after an application of a Btk-based formulation reported increases in the following symptoms after the spray: sleep problems; irritated throat; stomach discomfort; itchy nose; dizziness; diarrhea; gas discomfort; extra heartbeats; and difficulty concentrating.

The community survey’s authors stated that they could not confirm that these self-reported symptoms were due to the applications nor did they confirm that the symptoms had been diagnosed by healthcare providers. They state that there was no reported increase, by the people surveyed, in visits to either medical practitioners or alternative healthcare providers.

After a thorough review of the toxicity of Btk products, including both active and inert ingredients, the US EPA, Health Canada, the World Health Organization, and many other groups categorize Bacillus thuringiensis as a least toxic method of pest control.

Can the pesticide product Foray® 48B make people sick?
Studies of reported human health effects following applications of the organic version of Foray® 48B are not available.
Foray® 48B (EPA Registration No. 73049-427), which is to be used against gypsy moth in April & May 2016, was certified as organic by Organic Materials Review Institute (OMRI) in 2006.
Below are summaries of two studies of community applications of an older, conventional (non-organic) version of Foray 48B:
A study of an entire community in New Zealand was done for 2002 application of Foray® 48B. Surveys of 292 study participants about their own symptoms and their self-perceptions of their health were done before and after the spray. Among the findings: there were significant increases in the rate of reported throat and gastrointestinal symptoms, and for sleep problems, following the sprays. Yet symptoms of pesticide exposure are quite general, and are often the same as those from other causes such as flu or food poisoning. The study authors cautioned that these self-reported symptoms were not necessarily confirmed by healthcare providers. It is possible that the sound of early-morning helicopters was responsible for the sleep disturbances. Finally, most participants in the New Zealand study reported their health (and that of their children) were not affected by the spray program, nor was there any reported increase in visits to either medical practitioners or alternative healthcare providers.
There have also been concerns that aerial sprays of Btk-based pesticides, such as Foray® 48B, could impact vulnerable populations in the spray zone. Canadian researchers explored this issue during a 1999 application of Foray® 48B over Vancouver Island. The lung symptoms and breathing capacity (lung function) of 29 children with asthma living in spray zone were compared to those of 29 children with asthma living outside the spray zone. Measurements, as conducted by parents, were done before and after the spray period. There were no differences in asthma symptom scores between either groups, neither before nor after the spray. There were there no significant changes in measured lung function, as reported by parents of study participants, after the sprays.

What about the “other” or so-called inert ingredients in Foray® 48B?
OHA public health toxicologists have reviewed all the ingredients in Foray® 48B and confirmed that all are naturally-occurring in produce or made for use in food products. They are approved for use in food by the US Food & Drug Administration (FDA). According to the FDA, these ingredients are generally recognized as safe meaning that there is no evidence or suspicion that these ingredients are hazardous to people.
Because some ingredients are common in food, people with serious food allergies should review the advice below for people with allergies and weakened immune systems as well as what one can do before, during, and after the spraying.

What about people with weakened immune systems and people with allergies?
Although we don't have evidence that Btk will affect any given group of people, individuals with a weakened immune systems or serious food allergies may choose to avoid any potential for exposure by leaving the spray area during the application. People with weakened immune systems may include those with cancer, AIDS, or transplanted organs.
If you or someone in your home is concerned and cannot stay indoors or leave the area during the application, you might consider speaking to a health care provider. The Foray® 48B product may contain residues of grains, food additives, or preservatives. If you have serious allergies to these you might consider contacting your health care provider and taking steps (outlined below) to avoid exposure.

What should I do before, during and after the spraying?
On the application dates, people in the spray zones will see and hear (loud) aircraft flying above. Potentially they may fly very low. If you or someone in your home is concerned about the application due to a medical condition, please consult with a health care provider.
Foray® 48B is considered a low-risk pesticide product by the US EPA. If you are concerned, you can take the following steps before the spray and immediately after:
  • Close windows and doors and shutting off heating/ventilation systems that draw air from the outside into your home.
  • Cover playground equipment, sandboxes, benches, toys, pet dishes, and lawn chairs before the application, or hosing them off afterward.
  • Stay indoors (and keep pets indoors) during the application in your area. This allows droplets to settle and adhere to vegetation. Pets that go outside may brush up against vegetation that’s wet with spray, and bring it back inside the home on their fur. Consider controlling their movements when outside until spray is dry.
  • Wait 30 minutes or until the spray has dried before touching vegetation treated during the application. The time needed for the spray to dry depends on conditions at a particular location. These may include humidity, air temperature, and wind speed in the area.
  • Wash exposed skin with soap and water if direct contact with the spray droplets occurs.
  • If you are outside at the time of application and the spray droplets get into your eyes, flush with water immediately.
  • If you feel sick or have symptoms following exposure, contact the Oregon Poison Center at 1-800-222-1222 for further medical advice.
  • Learn about additional ways to avoid exposure:

What if I have more questions?
  • If you have been exposed to Foray® 48B and you have concerns about possible health effects, wash the affected area with soap and water and contact the Oregon Poison Center at 1-800-222-1222.
  • For non-urgent questions on Foray® 48B or Btk, contact the EPA-funded National Pesticide Information Center (NPIC), based at Oregon State University, by phone 1-800-858-7378 (M-F, 8AM-12PM) or email
  • You can learn more about pesticides on NPIC’s website, and review their Btk Fact Sheet, or their YouTube video on Bacillus thuringiensis (Bt)
  • For general information about applications of Foray® 48B, planned for April and May 2016, please contact Oregon Department of Agriculture’s (ODA) Plant Protection and Conservation Programs staff at 1-800-525-0137 (Mon. – Fri., 8AM – 5PM) or by email:
  • To hear pre-recorded information about the status of the project on the days that sprays are scheduled (or on weekends), please dial 211.
  • For more information on gypsy moth, visit:

What if I want advanced notification as to when spraying will occur? 
  • The Oregon Department of Agriculture will provide advanced notification to let you know when spraying will occur if you sign up to receive notifications.  To sign up, click the "Sign Up for AGM Info" button at the following link: 
  • You may also sign up for notifications and information by calling (ODA) Plant Protection and Conservation Programs staff at 1-800-525-0137 (Mon. – Fri., 8AM – 5PM). If after hours, please leave a voicemail with the information needed for the notification method(s) you prefer (see for details).
What if I have non-health concerns about these sprays?
  • During regular business hours: To express non-medical/non-human health concerns about the gypsy moth sprays, including concerns about environmental impact, please contact Oregon Department of Agriculture’s (ODA) Plant Protection and Conservation Programs staff at 1-800-525-0137. [Available: Mon. – Fri., 8AM – 5PM.] Staff can also be reached by email:
  • On weekends and outside of business hours: To express non-medical/non-human health concerns about the gypsy moth sprays, including concerns about environmental impact, please dial 211. Staff will ensure your report is sent to appropriate state agencies.