Carbaryl, Carbofuran, and Methomyl - National Marine Fisheries ...

Use Site
Maximum Single
Application Rate
(lb a.i./acre)
36
Application
Maximum
Number of
Applications
Minimum
Application
Interval
(days)
Maximum per
year
(lb a.i./acre)
Onions 0.9 8 x 3 crops 5 16.2
Spinach 0.9 8 x 3 crops 5 10.8
Turf 0.9 4 x 2 crops 5 7.2
Timing. The timing of application is dependent on use, but may occur throughout the
year. In most cases multiple applications are allowed to maintain pest control.
Applications occur on fruit crops during the bloom, petal fall, pre-bloom, and leaf stages
and when pest pressure is highest on a “When Needed” basis. On corn, application may
occur during the whorl/foliar stages. With other crops, application is during the foliar or
leaf stages of the crop (EPA 1998).
Metabolites and Degradates
Several degradates and metabolites have been identified for methomyl. The major
degradate in most metabolism studies was CO 2 . Another degradate, S-methyl-Nhydroxythioacetamidate,
which is highly mobile, appears primarily as a product of
alkaline hydrolysis. In an aquatic metabolism study, methomyl degraded with estimated
half-lives of four to five days. After seven days, acetonitrile comprised a maximum of
17% and acetamide up to 14% of the amount of methomyl applied. After 102 days,
volatilized acetonitrile totaled up to 27% of the applied and CO2 up to 46% of the applied
material (EPA 2003).
Species Addressed in the BEs
EPA’s BEs considered the effects of carbaryl, carbofuran, and methomyl to 26 species of
listed Pacific salmonids and their designated critical habitat. EPA determined that
carbaryl, carbofuran, and methomyl may affect most of these species. Exceptions follow:
EPA concluded that the registration of carbaryl products would have no effect on
Northern California steelhead, SONCCal coho, Hood Canal summer-run chum, and
Ozette Lake sockeye. EPA also concluded that the registration of carbaryl products