Evaluation of sustained efficacy against filth flies in response to increased levels of insect growth regulators delivered directly through beef cattle

Horn fly (Haematobia irritans), stable fly (Stomoxys calcitrans) and house fly (Musca domestica) populations remain a significant source of monetary loss for cattle producers. Methods to control these pests, including chemical insecticides such as diflubenzuron, are readily implemented in various cattle operations. Diflubenzuron (DFB) products are generally delivered to animals through feed supplements requiring host ingestion and expulsion into the manure where diflubenzuron can disrupt fly larval development. To ensure consistent and effective concentrations in the manure, DFB-containing products are often labeled for daily consumption. This treatment regimen can be achieved in intensive cattle operations where house and stable flies can be problematic. However, abiding by a daily treatment regimen can be difficult in rangeland systems in which horn flies thrive. Alternative treatment regimens might be more effective for rangeland cattle operations. The objective of this study is to determine if a higher dose of diflubenzuron delivered once every 48 hours differs from label rate efficacies. For this study, 12 animals were randomly assigned to 4 treatment groups. The first group (control) remained untreated. The second group (LR) was treated with diflubenzuron daily at the label rate, while the third group (LR2) and fourth group (DR) were treated with diflubenzuron every other day at the label rate and twice the label rate, respectively. No statistical difference was found between the LR and DR groups, indicating a similar level of control efficacy. These findings may offer insight into potential strategic implementation of diflubenzuron in extensive cattle operations to control filth flies.