Condensed tannins inhibit house fly (Diptera: Muscidae) development in livestock manure.

Reducing chemical use for suppressing internal and external parasites of livestock is essential for protecting environmental health. Although plant condensed tannins are known to suppress gastro-intestinal parasites in small ruminants, no research on the effects of tannins on external arthropod populations such as the house fly, Musca domestica L., have been conducted. We examined the impact of plant material containing condensed tannins on house fly development. Prairie acacia (Acacia angustissima (Mill.), Kuntze variety hirta (Nutt.) B.L. Rob.) herbage, panicled tick-clover (Desmodium paniculatum (L.) DC.) herbage, and quebracho (Shinopsis balansae Engl.) extracts were introduced at rates of 1, 3 or 5% condensed tannins/kg beef cattle, dairy cattle, and goat manure, respectively. In a second experiment, we also introduce purified catechin at 1 or 3% of dairy manure dry matter and measured its impact on house fly development. For the house flies used in these experiments, the following was recorded: percent fly emergence (PFE), average daily gain (ADG), and average fly weight (AFW). No effects (P>0.05) in house fly development were measured in the caprine manure. Prairie acacia (20.9% condensed tannins) had no effect on house flies developing in either bovine manures. Tick clover (4.9% condensed tannins) had a negative effect on all three quantifiable variables of house fly development in the bovine manures, whereas quebracho extract (64.0% condensed tannins) at the 3 and 5% rate reduced fly emergence in beef manure and average daily gain in dairy manure. The application of purified catechin at 3%, but not 1%, reduced fly PFE, ADG, and AFW.