Production of Stable Flies (Stomoxys calcitrans) from Sawdust Compost Barns and Straw Bedding Packs, Two Alternative Cold Winter Housing Systems for Dairy Cows.

Stable flies, Stomoxys calcitrans (L.), are important biting pests of dairy cattle and other livestock. These flies develop in decaying organic matter, such as soiled animal bedding. As part of a larger study of management options in organic dairy production, leftover debris from two winter housing systems, outdoor straw packs and indoor sawdust compost barns, were analyzed for the numbers and size of stable flies produced the following summer. The study was conducted at the University of Minnesota's West Central Research and Outreach Center in Morris. During winter, independently managed groups of 20 cows were housed from November to May in replicate housing systems. After the cows were moved to summer pasture, fly traps were assembled in the leftover piles (n = 4): emergence traps to quantify stable fly emergence and Olson traps to study ambient adults. The size of the emerged flies and 30 ambient adult females were measured. The sampled females were also dissected to determine the gonotrophic age. During peak emergence in both years, straw piles produced significantly more stable flies than compost bedding, but the adults were equal in size. The Olson traps showed adults were equally abundant at both sources. Over 60% of the females dissected were previtellogenic, indicating local emergence. Compost bedding is useful in managing stable fly numbers, while straw presents a serious stable fly production liability if not disposed of properly. [ABSTRACT FROM AUTHOR]