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


Date of this Version

January 2003


Proceedings of the 10th Wildlife Damage Management Conference. (K.A. Fagerstone, G.W. Witmer, Eds.). 2003.


Zinc phosphide has been used as a control agent for commensal rodents for over 60 years. Studies utilizing zinc phosphide as a population control agent were gathered and summarized to determine its efficacy when baiting the Norway rat, roof rat, house mouse, Peromyscus spp., prairie dog and ground squirrel. Efficacy information was abundant for rats, squirrels, and prairie dogs. However, efficacy data for baiting mice with zinc phosphide was limited. Overall the data show that in both laboratory and field testing, control levels of greater than 70% can be achieved for commensal rodent pests. Bait acceptance appeared to be the major factor in obtaining satisfactory control. However, the field efficacy can be greatly influenced by factors such as the time of year, geographic location, habitat treated and other environmental factors. Efficacy was significantly improved for all species by pre-baiting with clean bait prior to presenting bait containing zinc phosphide. Literature pertaining to both laboratory and field testing on rats was fairly extensive. Efficacy studies with mice, prairie dogs, and ground squirrels were conducted primarily under field conditions. However, a limited number of laboratory studies were located. No laboratory studies with ground squirrels were located. In general, once acceptable bait material and zinc phosphide concentrations were identified, zinc phosphide has proven effective at reducing populations of the Norway rat, roof rat, house mouse, Peromyscus spp., prairie dog and ground squirrel.