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United States Department of Agriculture

Agricultural Research Service

2008 Annual Report

1a.Objectives (from AD-416)
To gain a better understanding of stable fly population dynamics by elucidating their genetic structure throughout North America. To identify and characterize stable fly larval developmental sites and correlate larval production with adult population dynamics in relation to season, climatic variables and cultural practices. To determine the relative contributions of overwintering and migration to early season, colonizing, stable fly populations.

1b.Approach (from AD-416)
Methodologies to achieve the objectives include: Development of genetic markers and application of population genetic analyses to understand the structure of stable fly populations and the roles of migration and genetic drift in maintaining the observed structure. Surveys will be conducted to identify stable fly larval developmental sites. The production and phenology of developmental sites will be determined. Production will be correlated with adult populations to identify primary contributors to pest fly populations. Surveys will be conducted to identify stable fly overwintering habitats. Overwintering habitats will be characterized. Artificial overwintering habitats will be developed to study the environmental limits of overwintering stable flies.

3.Progress Report
Population Genetics of Stable Flies: Approximately 1000 microsatellite genotypes were developed from 9 population sites including New York, California, Florida, Nebraska, and Minnesota. Larval Habitat: Weekly core samples were taken to monitor immature stable flies at winter hay feeding sites and feedlot pens. The moisture content, pH, conductivity and ammonia levels were determined. Stable flies prefer to develop in moist (40-65%) and basic (pH 8-9.5) materials. Similar habitats were monitored for stable fly production with emergence traps. The number of emerging adult flies was monitored weekly. The traps were kept for 10 weeks before being moved within the site. Stable flies begin laying eggs in winter hay feeding sites in early April. Few adults emerge after mid-July. Laboratory Larval Media Studies: Larval media was altered by adding food preservatives. The addition of phosphoric acid, citric acid and nitrite promotes mold development and reduces stable fly development. Sorbic acid (0.25%) reduces mold growth and stable fly survival increases. Pupal Parasites: Small nylon screen bags containing 50 stable fly or house fly pupae were placed weekly at 10 locations in feedlot pen and winter hay feeding sites remaining in the field for 7 days. Pupae were held for 6 weeks to monitor parasite emergence. Hemoccult Assay: A technique using commercial Fecal Occult Blood test strips, Hemoccult, was developed to detect the remnants of blood in stable flies. The Hemoccult technique detected blood more than 8 days after a blood meal. Visual observations detected blood for little more than 24 hours after feeding. Hemoccult tested field populations indicated 45% of the flies collected on Alsynite sticky traps had blood fed. Visual analysis indicated that < 1% of those flies had blood in their guts. Stable Fly Spatial Dynamics: The relationship between the physiological status of the stable flies collected on Alsynite sticky traps and their proximity to confined animals is being assessed. Economic Impact of Stable Flies: A dynamic model was developed to estimate the economic impact of stable flies on livestock production with varying population levels, seasonality, and levels of impact.

New SY Hire: A chemical ecologist was hired to replace a field ecologist in December 2007. A botanical-based stable fly repellent has been identified. Chemical identification of the major repellent structures is complete. This repellent candidate reduces biting > 98%, and spatial repellency was found when tested on ovipositing females. This repellent candidate has adulticidal properties, with knock-down time at ~ 6 min. and killing time around 15 min. Soy wax-based repellent formulation tested in the feedlot repels stable flies for at least 3 hours (90°F). Several oviposition attractant compounds associated with aged horse manure have been tentatively identified. Volatile compounds associated with bacteria were identified, and may play important roles for stable fly oviposition selection.

National Program 104 Veterinary, Medical & Urban Entomology, Components I: Ecology & Epidemiology; II: Detection & Surveillance Technology; III: Biology & Physiology.

1. Modeling the Economic Impact of Stable Flies. The last estimates of the economic impact of stable flies on livestock production were published in 1991. At that time, stable flies were considered to be primarily pests of confined livestock and their impact upon pasture cattle was considered insignificant. Subsequently, stable flies have been recognized as primary pests of pasture cattle, however, this impact has not been quantified. We developed an explicit and dynamic model to estimate the economic impact of stable flies on livestock production systems. Results of this model indicate that stable flies cost livestock producers in excess of $2 billion per year; $1.3 billion of which can be attributed to their effects on pasture cattle. Quantifying the economic impact of pests is a necessary prerequisite to assessing and prioritizing their importance and also for informing producers of the importance and benefits of implementing control measures. Our findings have more than quadrupled the estimated impact of stable flies over previous estimates and identified a much higher than expected impact of stable flies on pasture cattle. This accomplishment addresses National Program 104 Veterinary, Medical and Urban Entomology, Component IV: Control Technology, Goal 4.3: Area Wide Control.

5.Significant Activities that Support Special Target Populations

6.Technology Transfer

Number of the New MTAs (providing only)1
Number of Non-Peer Reviewed Presentations and Proceedings4
Number of Newspaper Articles and Other Presentations for Non-Science Audiences1

Review Publications
Taylor, D.B., Berkebile, D.R. 2008. Sugar feeding in adult stable flies. Environmental Entomology. 37(3):625-629.

Floate, K.D., Coghlin, P.C., Taylor, D.B. 2008. An update on the diversity of Wolbachia in Spalangia spp. (Hymenoptera: Pteromalidae). Biocontrol Science and Technology. 18(7):733-739. Available:

Last Modified: 1/26/2015
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