Tetracycline is widely used as a biomarker for bait consumption by wildlife; tetracycline is incorporated into bones and teeth and can be detected by fluorescence microscopy several weeks postconsumption. During 2003, the United States Department of Agriculture distributed more than 10 million tetracycline-containing rabies-vaccine baits to control the spread of wildlife vectored rabies to humans, pets, and livestock. To estimate the percentage of target species consuming the baits, raccoons and skunks were collected in baited areas and teeth were analyzed for the presence of the biomarker. Several incidents of low biomarker detection rates prompted an investigation of the stability of the biomarker in the baits. Baits were collected at several points along the manufacturing and distribution chain. Baits were analyzed for free and polymer-bound tetracycline and the less active isomer epitetracycline. Results indicated that a portion of the tetracycline was converted to epitetracycline. Additionally, significant quantities of both compounds were trapped in the polymer, which is homogeneously distributed throughout the bait. The results of this study suggest that approximately 40% of the target quantity of tetracycline was unavailable for absorption. This situation could contribute to low biomarker detection rates and suggests that formulation modification should be considered.

Damage to ripening sunflowers by blackbirds is an important agricultural problem in the northern Great Plains. In an effort to reduce crop loss by non-lethal means, several insecticidal formulations were evaluated for potential bird repellency. One formulation, Lorsban w-4E, was highly effective in feeding studies with caged blackbirds. Chlorpyrifos (an organophosphate pesticide) is a registered insecticide and acaricide commonly used to control insects on sunflower, and is the active ingredient in Lorsban w-4E. To support further evaluation of chlorpyrifos repellency in field trials, a rapid, simple, high performance liquid chromatographic (HPLC) analytical method was developed to assess residues in sunflower seeds, which had been aerially sprayed. Control black oil sunflower seeds were cryopulverized, fortified with chlorpyrifos at 0.50 mg. g 21 , 5.0 mg. g 21 , 50 mg. g 21 , and 500 mg. g 21 , and extracted in 90% acetonitrile/10% 1 mM phosphate buffer (pH 4.5). Extracts were filtered and analyzed by reverse phase HPLC with UV detection at 230 nm, with one elution method for samples ranging from 5.00 mg. g 21 chlorpyrifos to 500 mg. g 21 chlorpyrifos, and a second elution method for samples ranging from 0.500 mg. g