Effects of granular pesticide formulations and soil moisture on avian exposure

Two experiments were conducted to evaluate the influence of granular carrier type, pesticide load per granule, and soil moisture on avian risk of adverse effects from granular pesticides. Bird behavior, survival, and brain and plasma cholinesterase activity were used to assess exposure. In the first experiment, silica and corncob granules formulated with fensulfothion at either 1/2 or 1/32 of the median lethal dose (LD50) were offered to captive house sparrows ( Passer domesticus ) in bands on dry soil. The corncob carrier and granules formulated with 1/2 the LD50 presented the greatest risk to birds. In the second experiment, fensulfothion was formulated on three carrier types (silica, clay, and corncob) and offered to house sparrows in bands on wet or dry soil. Overall, formulations with corncob as the carrier and dry soil conditions presented the greatest risk to birds. Wet soil conditions reduced the risk of adverse effects for all three granular carrier types, but the greatest risk reduction occurred with corncob and silica granules. Differences in adverse effects associated with various carrier types and soil moisture conditions can add complexity when assessing risk to birds from granular pesticides.