Environmental parameters associated with stable fly (Diptera: Muscidae) development at hay feeding sites

Authors: Friesen, Kristina; Berkebile, Dennis; Wienhold, Brian; Durso, Lisa; Zhu, Junwei - Jerry; Taylor, David

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/2016
Publication Date: 3/25/2016
Publication URL: http://handle.nal.usda.gov/10113/5493335
Citation: Friesen, K.M., Berkebile, D.R., Wienhold, B.J., Durso, L.M., Zhu, J.J., Taylor, D.B. 2016. Environmental parameters associated with stable fly (Diptera: Muscidae) development at hay feeding sites. Environmental Entomology. 45(3):570-576.

Interpretive Summary: Stable flies are blood-feeding flies that primarily attack cattle. Their painful bites induce host defensive behaviors that have metabolic costs, costing the US cattle industry >$2 billion/yr. Stable flies develop in a diversity of fermenting substrates including crop residue, silage, grass clippings, sewage biosolids, and even insect carcasses. Elimination of larval substrate through sanitation is the most effective management practice for stable flies, but is challenging to implement, in part, because an accurate definition of what a suitable substrate constitutes is lacking. This study had three goals; first, to evaluate physiochemical properties of larval substrates in relation to each other and second, to evaluate physiochemical properties over time. The third objective was to relate the physiochemical properties to the absence or presence of stable fly larvae. For this investigation, we concentrated our efforts on accumulated hay residue around winter hay bale feeders, a primary site of stable fly emergence in the spring. In general, stable fly larvae were recovered from moist, slightly alkaline substrate with relatively high levels of ammonium and an average temperature of 23°C. pH was relatively stable around 8.0, indicating the presence of a strong buffering system. All bacterial counts that were measured decreased over time except total coliforms. Apart from physiochemical and biological parameters, it is likely that an unexplained seasonal effect influences stable fly development. Further investigations on stable fly developmental habitats and phenology are needed.

Technical Abstract: Substrates composed of hay residues, dung, and urine accumulate around winter hay feeding sites in cattle pastures, providing developmental habitats for stable flies. The objective of this study was to relate physiochemical and microbial properties of these substrates to the presence or absence of stable fly larvae. Properties included pH, temperature, moisture, ammonium concentration, electrical conductivity, and numbers of coliform, fecal coliform, Escherichia coli, and Enterococcus bacteria. Each physiochemical sample was classified as a function of belonging to one of the three 2-m concentric zones radiating from the feeder as well as presence or absence of larvae. In total, 538 samples were collected from 13 sites during 2005–2011. Stable fly larvae were most likely to be found in moist, slightly alkaline substrates with high levels of ammonium and low temperature. The probability of larvae being present in a sample was the highest when the moisture content was 347% relative to dry weight and the average pH was 8.4. Larvae were recovered within all zones, with a nonsignificant, but slightly higher, percentage of samples containing larvae taken 2–4m from the center. All methods used to enumerate bacteria, except total coliform, indicated decreasing concentrations in hay bale residue throughout the summer. In addition to the environmental parameters, cumulative degree day 10C had a significant effect on the probability of observing stable fly larvae in a sample, indicating that unidentified seasonal effects also influenced immature stable fly populations.