Bio-Pesticide Management of Pasture Flies in the Great Plains Via a Push-Pull Strategy

Pasture flies threaten profitability of beef cattle production in the Great Plains. While horn flies have traditionally been the major fly pest of range cattle, in recent years stable fly populations have greatly increased. Fly control is confounded by having few conventional insecticides available for use and by documented or suspected resistance to current insecticides. These factors make fly management and protection difficult, creating a need for alternative insecticides such as plant-derived biopesticides, also known as repellents. Sprayable and encapsulated biopesticide formulations were tested on yearling crossbred (Simmental × Red Angus) cattle in a Push-Pull system against native stable fly populations. The Push-Pull strategy in this study used a repellent to "push" flies from some animals and "pull" them to animals treated with an insecticide, which would reduce fly numbers. Cattle were randomized into 4 treatments and stable fly populations were recorded by visually counting flies on all four legs and belly region of each animal. The 4 treatments included Push-Pull (half of the animals in the group were treated with a repellent, Geraniol (and half treated with an insecticide, permethrin), Push only (treated with repellent, Geraniol), Pull only (treated with an insecticide, permethrin), and Control (no treatment). Testing was done in adjacent drylot pens (44m x 7.6m) in 2013 and 2014, and in adjoining upland range pastures in 2015 (6.8 hectares). All animals were treated weekly in a holding chute and then released back into their treatment group. A repeated measures design was used. Although the stable fly population differed each year, results were similar across years and locations (drylot or pasture). Both treatments including repellent (Push only and Push-Pull), as well as the insecticide (Pull) treatment, had similar numbers of flies per animal (10.01, 9.97, 9.75, ± 0.67 respectively; P > 0.05). Overall, repellent only, insecticide only, and the combination of insecticide and repellent reduced stable fly numbers per animal (P < 0.05) compared with the untreated Controls (14.98 flies per animal). The biopesticide geraniol offers promise for incorporation into stable fly management programs for pasture cattle. However, besides reducing stable fly numbers on cattle, an implementation strategy compatible with ranching systems will be required.

 

 

Key words: Beef cattle, Bio-pesticide, Stable fly, Pasture