Release of Pyrethroids from Insecticidal Ear Tags1

Publisher Website
Google Scholar
Abstract
The pattern of release was characterized for 8% fenvalerate, 10% permethrin, and 5 and 10% decamethrin ear tags on cattle. The release rate of the fenvalerate ear tags declined from 3.9 mg/day at 10 days to 0.9 mg/day after 180 days on cattle. Permethrin tags released 6.5 mg/day at 10 days and 1.5 mg/day at 180 days. Both tags provided good control of Haematobia irritans (L.) on herds treated with one tag per cow. The first appearance of a population level of five hom flies per cow occurred in weeks 20 and 17 postinstallation of the fenvalerate and permethrin tags, respectively. At these times, the tags were releasing ca. 1.0 mg/day and 1.9 mg/day, respectively. After 10 days on cattle, the 10 and 5% decamethrin ear tags had a release rate of 6.55 and 1.93 mg/day, respectively. The values declined to 1.54 and 0.46 mg/day, respectively, after 180 days. The profile of insecticide concentration from the surface to center of the fenvalerate and permethrin ear tags was determined for tags that had been on cattle for 24 weeks and was found to take on a parabolic shape characteristic of the diffusion process. These studies indicate that the release of pyrethroids from insecticidal ear tags can be predicted from previously derived equations for the release of solutes from dissolved, monolithic systems. The information presented can be useful in the development of new or improved ear tag delivery systems.