Duration: 10/01/2001 to 09/30/2006

Administrative Advisor(s):

NIFA Reps:

Non-Technical Summary

Statement of Issues and Justification

Ranchers and veterinarians, as well as livestock entomologists in USDA, Land Grant Universities, and animal health companies concur that the stable fly, Stomoxys calcitrans, has in recent years emerged as a serious problem for grazing cattle in pastures and rangelands of North America (Foil and Hogsette, 1994). A meeting convened in North Platte in September, 1998, by Dr. S. E. Kunz (USDA-ARS, Kerrville, TX), Dr. R. Bohlander (DVM, Chair of the National Cattlemans research committee), and Dr. J. B. Campbell (research and extension entomologist, University of Nebraska) reviewed this problem and discussed research needs to address it. Ranchers and veterinarians in attendance all agreed that the blood feeding activity of stable flies cause pastured cattle to bunch together in dense aggregations. This behavior probably disrupts normal grazing behavior, results in reduced calf weaning weights of 20-30 pounds, decreases yearling weights by 30-40 pounds, increases injury to calves by stomping dams, and increases incidence of foot rot in cows. Also, bunched herds trample vegetation in fragile soils and thereby accelerate soil erosion (blowouts). The recommendations developed by the panel of experts participating in this meeting were that (1) research be conducted to determine the source of the stable flies on grazing cattle, and to develop control strategies to protect grazing cattle from the flies; and (2) action be taken by Cooperative Extension staff to provide information to beef and dairy producers about the problem and available solutions.

The research described in this proposal is vital to developing an IPM system for the stable fly on range and pastured cattle. The central component of stable fly control in feedlots and dairies is source reduction, which is effected through sanitation and manure moisture management that limits suitable habitat for the development of stable fly larvae. Insecticidal mists, premise sprays, and parasitic wasps are used secondarily, but they are less effective in the absence of source reduction. The same IPM approach might solve the stable fly problem in pasture and rangeland if the source(s) of the flies were known, and if effective and practical control methods were available. Unfortunately, source(s) of the stable flies on grazing are unknown, and existing control methods are ineffective, impractical, or both. The consequences of not providing a system for control of stable flies on range and pasture cattle will be a continuation of chronic irritation, along with losses in comfort and efficiency of the beef and dairy industries.

The research proposed is technically feasible and likely to succeed. Cooperative research from the several states and USDA-ARS entomologists will determine the origins of stable flies in range and pasture situations, and will develop integrated control systems that will provide producers with better stable fly management methods.

A multi-state approach will overcome several obstacles. First, a limited number of veterinary entomologists are available to work on this national problem, and they are employed in widely separate locations. A multi-state project will assemble a critical mass of researchers with complementary skills and resources. Second, a multi-state approach will facilitate geographical replication in field studies. Stable fly sources may be the same or different in the different states, and comparisons among regions will only be possible if research is coordinated and methods are standardized. Finally, fly movement may be local, regional or both. By coordinating efforts of participating states, it will be possible to evaluate movement on spatial scales not possible by individual investigators.

Likely impacts of successfully completing the work are that beef and dairy producers will have the knowledge and tools needed to manage stable flies in range and pasture. This will mean that producers will be able to increase calf weaning weights, increase yearling growth rates, and increase lactation rates of milk cows. These increases in productivity will easily exceed the likely increases in control costs, and will thereby improve the efficiency of forage-based beef and dairy production, and increase the profit margins for these producers.

The proposed work is consistent with national and regional priorities, as stated in the recently published, "Food and Agricultural Policy -- Taking Stock for the New Century." The project will enhance pest prevention, base pest management decisions on science, capitalize on the unique public sector role in agricultural research and extension, and encourage collaboration between ARS and CSREES institutions.

Related, Current and Previous Work

The stable fly has long been recognized as an important pest of confined cattle during the summer months (see Foil & Hogsette 1994). This blood-feeding fly has a painful bite, and cattle attacked by stable flies often respond by bunching together in dense aggregations. In addition, animals stamp their front legs, switch their tails and drop their heads in an effort to dislodge feeding flies. Bunching increases heat stress, and in turn reduces feed intake. In beef cattle, heat stress increases time and feed required to reach slaughter weight, and consequently, increases the cost of finishing the animals (Catangui et al. 1997). Similar effects on lactation rate of dairy cattle are presumed, but have not been demonstrated experimentally. A recent three-year study under S-274 (Campbell et al., 2001) has indicated that stable flies are also an economic pest of grazing cattle. Stable flies reduced the weight gains of unprotected steers by 0.2 kg/day in 84-day trials on pasture. This estimate of reduced growth rate was probably low, however, because topical permethrin, the best available insecticide, was inadequate, and fly movement from unprotected to protected herds was probably substantial. Much other research has been accomplished under preceding multistate research projects NC-154 and S-274, and this work has led to and clarified the objectives in the present proposal.

Larval development habitats and overwintering

In the feedlot environment, stable fly larvae develop in fermenting, urine-soaked mixtures of manure and feed at drylot perimeters, in moist feed spills, in silage residues, and in large rolled hay bales (see Foil & Hogsette 1994 for review). On dairies, stored manure spilled feeds and soiled bedding under young stock and in calf hutches are probably the most important sources of stable flies (Schmidtmann 1988). Stable fly immatures can overwinter in non-frozen portions of manure mounds and silage piles in the Northern Plains (Berkebile et al. 1994). Larval development sites other than those of confinement facilities have not been investigated, and it is not known whether larvae and pupae overwinter in shallower, surface habitats that freeze in winter.

Dispersal by adult stable flies on local and regional scales

Stable flies have been found to disperse 8 km in 2 hrs (Eddy et al. 1962) and 29 km in 24 hrs (Bailey et al. 1973), but the record is 225 km in an unknown amount of time (Hogsette & Ruff 1985). Average dispersal rates are likely to be slower (Hogsette et al 1989) and affected by presence of host cattle, local habitats and terrain. These data suggest two sources of stable flies in pasture and range are possible: they may originate locally in pasture and range, or they may be immigrants from neighboring or distant confinement facilities. Previous work has not simultaneously examined both possibilities.

Extent of movement on regional scales and corresponding breeding structure of stable fly populations in North America are unclear. Wind from local fronts may be responsible for long range transport of stable fly populations (Broce 1993). Using allozyme markers, Jones et al. (1987) observed genetic differentiation among populations in the panhandle of Florida, but more recent work failed to detect differentiation in populations from Canada to Texas (Krafsur 1993, Szalanski et al. 1996). Newer genetic markers such as microsatellite polymorphisms and amplified fragment length polymorphisms (AFLPs) may provide better markers of movement and genetic variation within and among different regions of the U.S.

A method for estimating adult age from pterin content of their heads and field temperatures antecedent to field collection was developed (Lysyk & Krafsur 1993) and used to assess age and survival of adult stable flies in Iowa. Longevities of males and females were equivalent and exponentially distributed (Krafsur et al., 1995); average lifespan was about 8 days during summer. Age grading is an established tool that can be used to draw inferences about the origins of flies in a given area.

Control tactics and population management

Source reduction: This tactic, aimed at minimizing larval habitat has long been recommended to control stable flies where cattle are confined. Thomas et al. (1996) showed that sanitation alone could reduce the number of adults in cattle feedlots by a season-long average of 33%. Sanitation might be a useful tactic in pastures and range if stable flies were shown to originate in focal substrates in those environments.

Insecticides: In general, producers are most willing to use insecticides at beef and dairy confinement facilities, because they produce quick and visible results. Materials applied either directly to cattle or onto adjacent substrates include pyrethroids and organophosphates. These compounds are short lived and are generally effective if applied on a regular basis (Mock & Greene 1989). Use of the same compounds and formulations for pastured cattle is impractical. Insecticidal ear tags are less effective against stable flies than against non-resistant horn fly populations.

Traps: Much research has been done to develop traps for sampling and control of stable flies (ess Gibson & Torr 1999). An effective sticky trap is constructed of Alsynite^. fiberglassthe Williams (1973) trap is two rectangles fitted together, whereas Broces (1988) modification is a cylinder of the same material. Rugg (1982) attempted to trap out a stable fly population, but concluded that the time required for recoating of sticky traps prohibited their use in most field situations. To overcome required maintenance, subsequent workers replaced sticky sleeves with an insecticide. Alsynite. panels treated with permethrin removed more than 30% of a stable fly population when deployed at a rate of one trap per five head of cattle in Florida (Meifert et al 1978). Similarly, efficacy of permethrin impregnated Orlon yarn on fiberglass panels was modest and limited to 6-8 weeks under simulated field conditions (Hogsette & Ruff, 1996). Torr et al. (1992) showed that pyrethroid impregnated fabric targets were effective for killing tsetse for approximately one year under field conditions, which suggests longevity of permethrin varies with substrate to which it is applied.

Recent research suggests stable fly traps could be made more attractive. Vale (1974) developed electric grid technology to study the trap approaching behaviors of tsetse identified odors and colors used by tsetse in host location and feeding behavior. Fabric targets, impregnated with insecticides and baited with synthetic host odors, were then developed (Vale, 1993). Preliminary studies of trap seeking stable flies have been conducted in Louisiana using the same grid technology. Alsynite^. cylinders were compared with the NZI trap (Mihok et al. 1995), a pyramidal device of blue and black fabric. The Alsynite^. trap captured 183 flies per hour, while the NZI captured 278 flies. These results suggest that a more attractive target could be developed, one which could be treated with permethrin (or alternative) and be deployed in pasture situations to protect grazing cattle.

Classical and augmentative biological control: Wasps in the genera Muscidifurax and Spalangia (Pteromalidae) are pupal parasitoids that are most promising (see Petersen 1989). Muscidifurax includes five species; M. raptor is endemic throughout the temperate and semitropical regions of the world, whereas another four are limited to the Western Hemisphere (Gibson 2000). Taylor et al. (1997) found mtDNA nucleotide substitution rates of 14-19% among M. raptor, M. raptorellus, and M. zaraptor. These levels of differentiation indicated divergence millions of years ago. Spalangia are more speciose in the Old World, and the subset of species now extant in the New World appear to have been introduced. Biological properties of Old World and New World forms of the same species in these two genera have yet to be compared.

Attractive features of pteromalid wasps is that they occur naturally in the environment, they can produce high levels of host mortality, and they can be mass-reared for field release. Parasitization of house fly pupae was increased in Florida following mass releases of S. endius (Morgan & Patterson 1977), and of M. raptor in dairies (Geden et al. 1992). However, attempts to control flies on larger, midwestern cattle confinements (see Greene 1990) and California dairies (Meyer et al 1990) were less successful. Natural prevalence and performance of pteromalid parasites released in pastoral settings and other habitats outside of cattle confinement facilities have not been evaluated.

Wolbachia: These alpha-Proteobacteria are obligate, intracellular symbionts that manipulate their hosts reproduction in different ways (Werren 1997). Of particular interest is cytoplasmic incompatibility (CI) in embryos that results from matings of males and females that lack the same strain of Wolbachia. In early experiments (reviewed in Sinkins et al. 1997), cytoplasmically incompatible Culex quinquefasciatus males were released into a Burmese village, resulting in a temporary elimination of the resident population. Dobson and colleagues (unpubl.) recently developed a mathematical model of Wolbachia infections and their effects on host population size. This model demonstrated that releases of Wolbachia-infected hosts that are bidirectionally incompatible with the target population can reduce or even eliminate the target population. Simulations predict that this strategy will be appropriate for controlling stable fly, because it has a suitably low reproductive rate (R₀) of 1.1-3.2. Examples of insects known to have multiple, bidirectionally incompatible Wolbachia include Drosophila simulans and Cx. pipiens. A key first step will be to survey stable fly populations in North America to determine which, if any strains of Wolbachia are now present, using diagnostic methods developed initially for Wolbachia in Aedes mosquitoes (Dobson et al. 2001).

Modeling: Simulation models are tools for understanding how complex systems function, and for evaluating and optimizing current and proposed integrated pest management (IPM) strategies and tactics (Focks & McLaughlin 1988; Wilhoit et al. 1991a). Models also aid in technology transfer, illustrating effects of management options to producers. Most of the basic relations needed to develop a stable fly model are in hand. Effects of temperature on stage-specific development time, survival and reproduction of stable flies were examined, reviewed and modeled by Lysyk (1998). Additional egg-larval mortality occurs in the field, and varies according to abundance of generalist predators (mainly staphylinid beetles and macrochelid mites), and pupal mortality varies with abundance of parasitoids (Lysyk 1995). The life cycles of the principal parasitoids have been described, and their functional and numerical responses have been studied in laboratory settings (Wilhoit et al. 1991a, Lysyk 2000). Efforts are underway (Lysyk, pers. com.) to code the component mathematical relationships into a process based simulation model driven by daily min-max air temperatures as available from NOAA, and inferred for corresponding larval-pupal substrates (Wilhoit et al., 1991b). Time series descriptions of stable fly abundance in Alberta and 7 states from NY to FL (S-274, unpubl.) are available to compare predicted (model) and observed (field) patterns in stable fly abundance. Features remaining to be understoodnamely, nature and supply of larval substrates, overwintering, and adult dispersalare subjects of objectives 1 and 2 in the present proposal.

Objectives

1. Identify, characterize and rank developmental habitats of stable flies and assess their overwintering success in those habitats.
   
2. Assess dispersal by stable flies on local and regional scales.
   
3. Develop sustainable management strategies and tactics that will be adopted by producers.
   
4. 
   

Methods

Measurement of Progress and Results

Outputs

• <I><P>Outputs of Objective (1)</I> will be quantitative descriptions of the relative fly production potential of different substrates around representative farmsteads in the major cattle producing regions of the country. <I>Outcomes</I> will be that producers will be able to rank likely sources of stable flies and target prevention and source reduction efforts accordingly.</P>
• <I><P>Outputs of Objective (2)</I> will be statistical and mathematical descriptions of fly movement (km<SUP>2</SUP> per day) by adult stable flies on different kinds of landscapes, and an understanding of the extent of larger scale movement of individuals and their genes within and among regions. <I>Outcomes</I> will be that producers will be able to define the spatial scale at which source reduction will need to be practiced. </P>
• <I><P>Outputs of Objective (3)</I> will be field-level evaluations of source prevention measures, new traps, new insecticides, and possibly new biological control agents (Eurasian pteromalids and <I>Wolbachia</I> strains). Furthermore, output of the modeling effort will be an understanding of the magnitude of control effort, using the best available tactics, and the geographic scale at which they must be applied to effect a desired level of population suppression. </P>

Outcomes or Projected Impacts

Milestones

(2002): <Ul><LI>Larval habitats censused (localities to be determined) <LI>Mark-release-recapture (M-R-R) completed at one location (to be determined) <LI>Spring and autumn pupae from all participants to ARS-L, KSU and UKY <LI>Genetic markers (ARS-L), and NAA (KSU) screenings begun; depends on spring pupae <LI>Existing and new spring heads collected (UMN, Cornell) and age graded (KSU) <LI>New trap designed (LSU) <LI>Chemical controls evaluated (UNL) <LI>Eurasian parasitoids evaluated (UMN, ARS-FL, ARS-L) <LI>Initial stable fly model coded and evaluated (Lethbridge, UMN) <LI><I>Wolbachia</I> screenings begun (UKY); depends on pupal samples</ul>

(2003): <ul><li>Larval habitats censused; depends on censuses in 2002 <LI>Overwintering study set up; depends on censuses in 2002-3 <LI>M-R-R studies done at additional localities (to be determined), depends on MRR in 2002 <LI>Genetic markers (ARS-L) and NAA (KSU) screenings completed, depends on spring and autumn samples from 2002 <LI>Spring fly samples collected and age graded; depends on age grading in 2002 <LI>Trap design optimized (LSU) <LI>More chemicals evaluated (UNL) <LI>Eurasian parasitoids evaluated (UMN + ARS-FL); depends on progress in 2002 <LI><I>Wolbachia</I> screenings completed (UKY); depends on pupal samples <LI>Stable fly model refined; depends on 2002 censuses and M-R-Rs </ul>

(2004): <ul><li>Overwintering study completed, depends on 2002-3 censuses and 2002 setup <li>2<SUP>nd</SUP> overwintering study set up; depends on 2002-3 censuses and 20034 overwintering <li>Trap out tested nationally (LSU + others); depends on 2003 trap design <li>Chemicals tested nationally (UNL + others); depends on 2003 evaluations <li>Eurasian parasitoids evaluated (UMN + ARS-FL); depends on 2003 evaluations <li><I>Wolbachia</I> effects tested (UKY); depends on 2003 screenings <li>Stable fly model refined; depends on 2003 censuses, M-R-Rs and tactic evaluations</ul>

(2005): <ul><li>Winter feeding and spring source reduction study completed, depends on 2003 censuses and 20024 overwintering <li>Trap out tested nationally (LSU + others); depends on 2004 results <li>Competing IPM programs designed and tested (all); depends on 2004 modeling <li>Stable fly model refined; depends on 2003-4 overwintering and tactic evaluations</ul>

(2006): <ul><li>Winter feeding and spring source reduction study completed, depends on 2003 censuses and 20024 overwintering <li>Competing IPM programs refined and tested (all); depends on 2005 results</ul>

(0):0

Projected Participation

View Appendix E: Participation

Outreach Plan

Many avenues will be used to make the results of this research available to beef and dairy producers in the U.S. Results will be posted on the projects multistate research web site, which is linked to other web sites including the Regional IPM Center web sites. The information will be provided to livestock extension educators in the various states and will be used in continuing education programs for the states veterinary associations. The information will also be disseminated to the states beef and dairy associations such as the Cattlemens Associations, to beef cattle trade publications such as "Beef," and to farm publications like the "Nebraska Farmer," which has similar trade journals in the various states. Similarly, Hoards Dairyman and other venues appropriate to dairy producers will be utilized. Original research data will also be published in scientific journals and presented at regional and national science meetings. One of the best meetings for presenting useful livestock insect information is at the annual Livestock Insect Workers Conference which is attended by most federal, state, extension and animal health veterinary entomologists. The data will be included not only in research journals but in extension fact sheets as well. In addition, most extension personnel have access to electronic media including television and radio farm programming. In summary, the research progress will be disseminated by many methods that are used to gain production information by the industries producers.

Organization/Governance

Organization will be as prescribed in the Guidelines for Multistate Research Activities. Component research projects will be planned and coordinated by the technical committee. Members with voting status will consist of a representative from each cooperating SAES who is appointed by the respective Director, and a representative from each cooperating ARS and Ag-Canada laboratory as authorized by the laboratorys administrator. The committee will also have an Administrative Advisor (non-voting status) and a consulting member representing Cooperative States Research Extension Education Service (CSREES) (non-voting status).

Officers of the Technical Committee will consist of Chair-elect, Chair, and Secretary. Officers will serve for 2-year terms, and rotate through the remaining offices (in order as listed) in 2-year terms. The three officers will be elected at the first meeting of the Technical Committee, and a new Chair-elect will be elected in succeeding alternate years. The Technical Committee will meet at least once each year, usually in winter, to discuss project results and plan subsequent work. The Chair will consult with the Technical Committee and Administrative Advisor regarding meeting dates and locations. The Advisor will authorize and announce meetings to the Technical Committee. The Chair will set meeting agendas, lead meetings, and supervise preparation of the annual report of project work. The Chair-elect will assist the Chair as requested, and serve as Chair in his or her absence. The Secretary will record minutes of meetings. Reports and minutes will be submitted to the Administrative Advisor for appropriate distribution, and will be posted on the projects web site within 60 days of each meeting.

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Attachments

Land Grant Participating States/Institutions

AR, FL, KS, KY, LA, MN, NE, NM, NY, TN, TX

Non Land Grant Participating States/Institutions

Agriculture Canada, Lethbridge, USDA-ARS, USDA-ARS/Florida