Pesticide Info

We are attempting to post here the latest information on pesticides used in Washington State to eradicate gypsy moths.

Current Topics

Foray 48

Foray 48 (also known as Foray 48B, Foray 48F, Foray 76 and Foray XG in slightly different formulations – we use “Foray 48B” to cover all of these except when appropriate) is an insecticide used to selectively kill the larval stage of the family Lepidoterae (butterflies and moths). It is composed of an active ingredient, a bacteria called Btk (see below) and mostly “inert” ingredients. It is produced currently by Valent Biosciences. Foray 48B is often used as the pesticide of choice to eliminate gypsy moths, tussock moths, painted apple moths, and others all over the world.

While there are no studies that show more than a handful of serious health effects from spraying Foray 48B, no really comprehensive studies have ever been conducted. The new label states that Foray 48B can be used on food crops (the previous label stated it could not be used on food crops, and no obvious research was done to justify the change in status), but that workers should be outfitted with particulate filter masks and protective clothing, and stay out of the fields once sprayed. Even for non-agricultural uses, the label requires applicators to “keep unprotected persons out of the treated areas until sprays have dried.” You can download the latest US FIFRA labels for the Foray products as follows:
Foray 48B label
Foray 48F label
Foray 76B label
Foray XG label

To see the original Foray 48B label (still valid, although not the legal label), which has somewhat more alarming language, click here.

The MSDS (Material Safety Data Sheet) for Foray 48B states that the carcinogenicity, mutagenicity, and other effects are essentially unknown or untested. The majority of Foray products are made up of “inert” or “other”  ingredients, which are not available to the public but could be made up of materials even more toxic than the active ingredient. Download the latest MSDS for the Foray products:
Foray 48B MSDS
Foray 48F MSDS
Foray 76B MSDS

Some possible inerts have been discovered by citizen groups. These are publicly available, and as of 2004 listed here.

Recently, scientists at the University of British Columbia “reverse engineered” a batch of Foray 48B to see what might actually be in it, and presented the results (the full report is no longer posted on the web). They analyzed both volatile and non-volatile compounds in Foray 48B. Without more information, they were unable to identify the non-volatile compounds, some of which probably were the active ingredients. However, they did manage to identify with a fair amount of confidence compounds in the following list. It could be that some of these chemicals are the result of decomposition of other compounds or byproducts of cellular processes, so the actual number of inerts added could be less. Even so, it is startling that there are many more than the half-dozen or so inert ingredients that Valent claims are in Foray 48B.

The inerts are listed by chemical name and CAS number. In addition, if they are on the EPA’s lists of inert ingredients, their classification is listed in the third column. List “3” are “inerts of unknown toxicity”; List “4B” are “inerts generally considered to be safe for use in pesticides.” [An aside – the way an inert gets on List 4B is that a company asks for it to be put there. No testing is actually performed.] Notice that most of these compounds are not listed with the EPA as permissible inert ingredients. The significance of this is unknown. This analysis was performed on a batch of Foray 48B prior to a possible reformulation, so the composition now may be slightly different.

Analysis – Our guess is that BIT was added after 1999 as a preservative.  The siloxane (organosilicone) compounds are probably added as surfactants (wetting agents) or anti-foaming agents, or may be indicative that Valent used an organosilicone-based methylated vegetable oil as a carrier/wetting agent. The butylated hydroxy toluene (BHT) likely slows oxidation of the vegetable oil carrier. Acetic acid and benzoic acids may have been used to stabilize the pH of the mixture. Sydnone may be a dye used to color the product. Galacticol, 2-hydroxy pyridine and trimethyl phosphine are likely products of fermentation or decay of the bacteria or growth medium.

Table of Probable Volatile Inerts in Foray 48B from UBC Study (1999):

Formula CAS Number EPA Inerts Designation
1,5-hexanediene-3,4-diol, 2,5-dimethyl 4723-10-8
1-propanesulfonyl chloride 10147-36-1
2 methyl-2,3-pentanediol 7795-80-44
2,4-hexadienedioic acid 505-70-4
2-butanone, 4-acetyloxy 10150-87-5
2-heptanone, 3-hydroxy-3-methyl 13757-91-0
5-hexene-2-one, 5-methyl 3240-09-3
2-hydroxy pyridine 142-08-5
acetic acid, 2-propenyl ester 591-87-7
acetic acid, anhydride 108-24-7 4B
acetic acid, mercapto -,methyl ester 236-48-2
benzoic acid 65-85-0 4B
benzoic acid, siloxane derivative 10586-16-0
benzoic acid, 2-hydroxy-,phenyl ester 118-55-8
butylated hydroxy toluene 128-37-0 3
cyclohexasiloxane, dodecamethyl 540-97-6
cyclopentasiloxane, decamethyl 541-02-6 3
cyclotetrasiloxane, octamethyl 556-67-2 3
cyclotrisiloxane, hexamethyl 541-05-9
disiloxane derivative 1438-82-0
disiloxane derivative 18420-09-2
ethanol, 2-(1methylethoxy)- 109-59-1
ethanol, 1-methoxy-,acetate 4382-77-8
ether, sec-butyl isopropyl 18641-81-1
ethylene diamine 107-15-3 3
galacticol 608-66-2
penta siloxane, dodecamethyl 141-63-9 –
phenyl amine R silane derivative 10538-85-9
phosphine, trimethyl 594-09-2
sydnone, 3-(phenylmethyl) 16844-42-1
thietane 287-27-4
trisiloxane 3555-47-3 3

During aerial spraying, the concentration of these products (just the volatile compounds) was not detectable down to the limit of the equipment used. This is in the parts per million (how many parts is not clear).

You can see more about inert ingredients at Beyond Pesticides Inerts Info Page. [Outdated link: contact Beyond Pesticides for information]. There are some good reports you can view at the entry “Inerts.” Also, see the information on this page for BIT.


Bacillus thuringiensis var kurstaki or Btk is a bacteria that is related to a natural bacteria (Bt) found in soil at extremely low concentrations. Btk strains in Foray 48B are not commonly found in soil. Researchers found a mutant strain of Btk, generically called an HD-1 type, in a sample and selectively bred it for maximum activity against caterpillars. Btk strains used in commercial pesticides are not found in any significant quantity in their present form (yet!) in nature and may be genetically modified; some have been patented (it is not possible to patent a natural life form). For a better understanding of how Btk works, see our short Bt primer.

All subspecies of Bt produce a substance, called a protoxin, that becomes poisonous when it is ingested by target insects (caterpillars for Btk). The only reason we are not poisoned is that the acid in our digestive tract deactivates the protoxin. However, this might not be completely true if you inhale Btk protoxin. Btk is also toxic in its own right; in the lab it has been observed to destroy cell walls in animal tissue.

It is claimed that Btk is a natural insecticide that is found in the soil and is used on organic crops. This is only partly true. While Btk is used somewhat today as an organic pest control, there is increasing awareness in the organic farming community that Btk could soon be a genetically modifed organism and probably should be avoided. When we eat vegetables or fruits sprayed with Btk, we only swallow a tiny amount of it, especially since most of the Btk is destroyed by the UV in sunlight after a few days of exposure. During a neighborhood spraying one would expect to inhale more Btk spores than would be consumed in a year’s worth of food. In addition, Btk is inactivated to some extent by ingesting it, but it spores may germinate and temporarily colonize the human respiratory tract after sprayings. Btk insecticidal strains produce protoxin at a level higher than that of the organisms commonly found in soil. The protoxin itself is isolated as a chemical (called crystalline protoxin or parasporal inclusion bodies) and mixed with the Btk in Foray 48B.

No Spray Zone maintains an active survey of health literature on Btk, some of which is found on our Btk Information Page. There are other web sites about reduction in pesticide use and appropriate alternatives to pesticides, such as the  Journal of Pesticide Reform. Note: JPR is no longer published and is archived. Contact NCAP at the above link for more information – they have fact sheets on alternatives.



Plyac is the trade name of a mixture of emulsifiable oxidized polyethylene and ethoxylated phenoxy ethanol. Ethoxylated phenoxy ethanol is one of a group of synthetic surfactants called “alkyl phenoxy ethoxylates (APE)” or “ethoxylated phenoxy alcohols.” Surfactants are chemicals that lower the surface tension of water and allow a substance to spread thinner and farther when it is applied. Surfactants are used in detergents, all-purpose cleaners, and hard surface cleaners. APE’s quickly break down into another class of compounds called nonylphenols (NP). NP’s are slow to biodegrade in the environment and have been implicated in chronic health problems. Researchers in England have found that in trace amounts of NP activate estrogen receptors in cells, which in turn alters the activity of certain genes. For example, in experiments they have been found to stimulate the growth of breast cancer cells and feminize male fish. One member of this family of chemicals (nonoxynol-9) is used as a common spermicide as well as an industrial floor cleaner, indicating the general level of high biological toxicity associated with these compounds.

APE’s routinely contain the contaminants ethylene oxide and 1,4 dioxane (not dioxin), both well-known carcinogens. Poly(oxy-1,2-ethanediyl),a-isooctadecyl-w-hydroxyl, an ethoxylated alcohol used in a surfactant larvacide, can contain up to 0.002% 1,4 dioxane. There is no data on the inhalation risk of these compounds.

The March 2002 issue of the Washington Free Press has a very good article on the pervasive effects of endocrine disrupting chemicals in the environment, and mentions specifically “alkylphenols”, a synonym for APE.

Plyac is mixed with Foray 48B to help spread the pesticide evenly on surfaces and make it stick better. Plyac or a similar compound is almost certainly one of the “inert” ingredients of Foray 48B.

BIT (1,2-benzisothiazolin-3-one) CAS 2634-33-5

BIT has been positively revealed to be one of the “inert” ingredients in Foray 48B. BIT is a “biocide” (a disinfectant) that is used as an additive to paints, for example, to prevent the growth of unwanted bacteria, yeasts, or molds. It probably is being used in Foray 48B to prevent growth of organisms other than Btk while the material is being shipped and stored.

BIT was banned in 2001 from being discharged into the environment in the Netherlands because it is toxic to aquatic life and because there are troubling issues with human interactions.  A conclusion from their government health ministry report: “Refined risk assessment shows that BIT (1,2-benzisothiazolin-3-one) is a very hazardous substance [when used in certain applications]” You can  view the full report here (see pages 31-32).

The US EPA has listed BIT as a probable immunotoxicant – not a good thing to spray around people or any other life form for that matter. Small amounts of BIT might be expected to cause sensitization or allergic reactions after exposure. The EPA also has no data as to the inhalation risk.

More Information on Plyac and BIT Toxicity

You can read this set of comments on an application to spray Foray 48B. It contains more detailed information about the toxicity of APE’s and BIT.

Info on gypsy moth spraying