Intake and efficacy of methoprene and stirofos mineral blocks for control of horn flies (Diptera: Muscidae) on pastured beef cattle
1993
Moon, R.D. | Noetzel, D.M. | Johnston, L.J.
Pastured herds of Shorthorn beef cattle, Bos taurus L., in western Minnesota were treated with different insecticidal mineral blocks during the summers of 1990 and 1991. Treatments were noninsecticidal blocks (MoorMan's 646-B Special Range Mineral Block A), 0.02% methoprene blocks (MoorMan's 650-B), and 0.5% stirofos blocks (Sweetlix). Mineral intake was monitored once or twice per wk. To evaluate efficacy, identified animals from the three herds were commingled for 18 h in one pasture to allow naturally occurring horn flies, Haematobia irritans irritans (L.), to oviposit in the animals' dung pats. Just before adults emerged, horn fly puparia were extracted to assess the effects of the insecticidal minerals on the developing flies. Intake of all three blocks varied substantially among weeks but most often exceeded prescribed rates. Methoprene blocks consistently increased pupal mortality, but offsetting increases in pupal densities negated effectiveness. Stirofos blocks did not increase larval mortality. Neither insecticidal block effectively prevented within-pasture production of horn flies under field conditions.
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