A potential means for deterring the spread of brown treesnakes from Guam is to apply a fumigant to outbound cargo. Products already registered with the U.S. Environmental Protection Agency (USEPA) for fumigation were tested by NWRC scientists, and methyl bromide was found to be highly effective against the snakes. However, when methyl bromide was also found to be an ozone reducer, attention shifted to two other fumigants: sulfuryl fluoride and magnesium phosphide. Methyl bromide is now also registered with the USEPA for use on treesnakes and registrations for sulfuryl fluoride and magnesium phosphide are pending. There is limited potential for application of cargo fumigants as the compounds are highly toxic, expensive and difficult to apply.
NWRC scientists also began looking at oral toxicants, initially pyrethrins (plant compounds for controlling insects) because these compounds are already registered with the USEPA. Ultimately, the pyrethrins showed limited efficacy for killing brown treesnakes. Subsequently, an NWRC researcher investigated over-the-counter analgesics and found that acetaminophen was highly toxic to brown treesnakes, even at low-levels (the 80-mg tablet used is equivalent to a children's dose of acetaminophen). Also, brown treesnakes will eat dead mice. Thus these mice, with acetaminophen inserted, can be used as a bait delivery system. The toxic baits can be placed in bait stations around buildings and fences, etc. or used in wide-scale broadcast efforts, accomplished with aircraft, for the treatment of the interiors of large or inaccessible areas.The mice/acetaminophen method of control is registered with USEPA. (see label)
Tests have shown that baiting poses minimal risks to crows, coconut crabs or land hermit crabs. Thousands of hours of video monitoring of dead mouse baits and snake carcasses in the field showed that risks to nontarget species were negligible.