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

Application Rate Water Depth A.i. Concentration in Surface
Water
(lbs a.i. / acre) (meters) (μg/L)
0.25 0.1 280
0.5 0.1 560
1 0.1 1121
3 0.1 3363
10 0.1 11208
Pesticide drift
We also provide estimated pesticide concentrations in shallow off-channel habitats associated
with drift from terrestrial applications of pesticides (Table 52). These estimates were derived
using the AgDrift model and estimate downwind deposition from pesticide drift (Teske 2001).
Additional deposition from runoff was not considered. The drift estimates derived represent
mean projected drift. Although AgDrift adequately predicts drift, its field validations studies and
other research show drift is highly variable and influenced by site-specific conditions and
application equipment (Bird, Perry et al. 2002). No-spray buffer zones (or setbacks) may
significantly reduce pesticide exposure to salmonids by reducing runoff and drift inputs.
The methomyl RED requires label statements for methomyl products that specify not to “apply
by ground equipment within 25 ft, or by air within 100 ft of lakes, reservoirs, rivers, estuaries,
commercial fish ponds and natural, permanent streams, marshes or natural, permanent ponds.
Increase the buffer zone to 450 ft from the above aquatic areas when ultra low volume
application is made (EPA 1998).” This label requirement appears to address many, but not all
aquatic habitats used by listed salmonids. For example, labels specify buffers to natural and
permanent streams, marshes, and ponds but there is no mention of important intermittent aquatic
habitats or manmade watercourses such as floodplain restoration sites and irrigation systems that
either contain listed species or drain to such habitats.
Specific buffer zones that correspond to current label requirements for carbaryl, carbofuran, and
methomyl were assessed (Table 52). No buffers to aquatic habitats are required by EPA for
carbaryl or carbofuran products. However, we did consider interim “voluntary” buffers
recommended by CDPR to protect federally listed endangered species
(http://www.cdpr.ca.gov/docs/endspec/prescint.htm). Our simulations assumed the off-channel
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