U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Document Type


Date of this Version



Published in Pestic Sci 55:553-557 (1999).


During a product-performance test of 2% zinc phosphide (Zn3P2) steam-rolled-oat groats (11.2 kg ha-1) to control voles (Microtus spp) in alfalfa (Medicago sativa), randomly located, brushed-dirt plots were used to assess broadcast distribution and remova/acceptance of placebo particles. Results showed that the Spyker® Model-75 Spreaders were calibrated adequately, with placebo baits broadcast uniformly onto plots [x ± SD = 3.5 (±2.7) groats 930 cmp-1]. Acceptance of the placebos by voles increased rapidly - 28% and 60% by 24h and 48h post-broadcast, respectively. Analyses of variance confirmed the uniformity (non-significance) of particles broadcast among enclosures/plots and the significantly greater removal/acceptance of placebos across days. This technique affords an objective decision-making tool for applicators and researchers applying Zn3P2 baits in field situations - an objective technique of assessing pre-bait acceptance that should improve efficacy of the rodenticide.