Using Parasitoids in an Integrated Pest Management Approach to Control Flies on Dairy Farms

Final Report for LS04-160

Project Type: Research and Education
Funds awarded in 2004: $288,000.00
Projected End Date: 12/31/2008
Grant Recipient: University of Arkansas
Region: Southern
State: Arkansas
Principal Investigator:
Kelly Loftin
University of Arkansas CES
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Project Information

Abstract:

Parasitoids were used to assist in fly control on southern dairy farms. Dairies using parasitoids in integrated pest management programs had similar fly numbers and parasitism as dairies not using parasitoids, emphasizing that sanitation and other methods of fly control are necessary when using parasitoids. Several naturally-occurring parasitoids were identified and this data increased the knowledge on diversity, abundance and seasonal distribution of parasitoids impacting flies in southern ecosystems. Deficiencies in quality assurance of commercial parasitoids that will impact the effectiveness of this approach were identified. Producer adoptable approaches for monitoring parasitoid quality and general fly IPM methods were developed.

Project Objectives:

The objectives of this proposal to use parasitoids in an integrated filth fly management program are:

1. Determine the species, seasonal occurrence and numbers of pupal parasitoids (Pteromalidae) that are naturally present in Arkansas, Mississippi and North Carolina dairy agroecosystems.

2. Evaluate parasitoid dispersal and level of filth fly pupal parasitism after release of wasps in the dairy agroecosystem. Objective 2 will be accomplished through releases of (a) commercially available parasitoids and (b) red-eyed strain of parasitoids. Releases of red-eyed M. raptor will be used to evaluate parasitoid dispersal relative to established release rates to optimize fly control with parasitoids.

3. Transfer integrated filth fly management technology to dairy producers and evaluate their efforts integrating parasitoid wasps into filth fly management programs.

4. Educate dairy producers, extension agents, and other dairy-related personnel in each state relative to parasitoid effectiveness and use as a tactic to include in an integrated filth fly management program.

Introduction:

Statement of Problem, Rationale and Significance: The house fly, Musca domestica L. and the stable fly, Stomoxys calcitrans L. are the major fly pests in and around dairy housing systems in the southern United States. Lower milk production, reduced feed conversion efficiency, community nuisance problems and public health concerns about unsanitary milk handling conditions are among the problems caused by these pests. Manure and decomposing feed create an ideal habitat for the production of house fly and stable fly larvae. Proper handling and disposal of waste materials around dairy facilities are critical in the management of fly populations. Sanitation is the most effective method of reducing fly populations and it is cost effective compared with the use of insecticides (Rutz and Pitts, 1999) but in practice, producers find it difficult to clean all potential larval habitats on a regular basis because of time and economic restraints and are often unaware of the large number of flies that can be produced by a small patch of suitable waste materials scattered around dairy facilities.

Dairy producers can no longer rely solely on pesticides for control of flies. The decreased availability of new insecticides has generated problems for pest management in dairies by requiring the use of only a few insecticide active ingredients, which has resulted in high levels of pesticide resistance in filth fly populations (Rutz et al., 1994). Relying on an integrated fly management approach including manure management that is augmented with biological control by relying on parasitoids plus cultural and chemical controls to minimize pests, is necessary. Such a strategy will help to insure the long term success of IPM programs and to conserve insecticides. Interest in biological control agents for the suppression of peridomestic muscoid flies on dairies is growing. Aware of the increasing cost of insecticides, decreasing availability of new chemicals and the development of insecticide resistance in resident fly populations (Scott et al. 1989), farmers are beginning to recognize the cost effectiveness of holistic integrated pest management strategies.

Preliminary data on two family farms in Arkansas in 2000 showed that the use of parasitoids coupled with restricted chemical use in an IPM program resulted in satisfactory fly control (Pennington et al., 2001). The use of parasitoids was comparable in costs to more conventional methods of fly control, allowing dairies to maintain a sustainable fly management system. In 2001 and 2002, the number of dairy farms using commercially available parasitoids to control flies expanded to eight and six, respectively. The Arkansas Dairy Cooperative received a SARE producer grant to expand demonstrations and make additional producers and industry personnel aware of the benefits and limitations of using parasitoids for fly control on dairy farms. These preliminary studies reinforced that proper manure management is necessary to control flies when utilizing parasitoids. Effective fly control should also help sustain the economic viability of small- and medium-sized family dairies and the economic development of the rural economy in the area.

Literature concerning natural occurring parasitoids attacking filth flies in southern dairy production systems is limited. Rutz and Axtell (1980) examined house fly parasitoids associated with poultry production in North Carolina and found eight pupal parasitoid species. Dry 2007 studied the occurrence and seasonal distribution of house fly pupal parasitoids in northwest Arkansas poultry facilities. Greater knowledge of the naturally occurring parasitoids present around the dairy facility and optimal release rates of the parasitoids should allow for more effective use of parasitoids.

Literature Review: The house fly, M. domestica L. and the stable fly, S. calcitrans L. are the major fly pests in and around dairy housing systems in the southern United States. Stable flies impact both milk production and feed efficiency, although these estimates of losses vary. Stable fly infestations reduce milk production 40-60 percent (Drummond et al. 1981). Similarly, a reduction in growing ration efficiency of nearly 13 percent was observed with a stable fly infestation of 50 flies per calf (Campbell et al. 1977). The threat of mechanical transmission of pathogenic organisms by the house fly is well documented. This threat is increased in production systems where animals are in close confinement and is a concern with the possibility of bioterrorism.

Potential milk contamination as a result of treating with insecticides is also a major concern to dairy producers and milk marketing agencies. Moreover, inadequate fly control in cases of severe infestation can result in stopped sales of milk or reduction of grade of milk sold (Lancaster and Meisch, 1986). In addition to these problems, stable flies and house flies create an uncomfortable environment for farm workers, create community nuisance problems and disrupt feeding habits of cows. The manure and decomposing feed around dairy facilities create an ideal environment for the production of house fly and stable fly larvae. The practices associated with the handling and disposal of waste materials around dairy facilities are critical in the management and control of fly populations. Sanitation is the most effective method of reducing fly populations and it is cost effective compared with the use of insecticides (Rutz and Pitts, 1999). However, in practice, producers find it difficult to clean all potential larval habitats on a regular basis because of time and economic restraints and they are often unaware of the large number of flies that can be produced by a small patch of suitable waste materials scattered around dairy facilities.

A large proportion of the fly breeding on most dairy farms occurs in calf housing and cattle resting areas where manure and bedding materials can accumulate for months before clean-out (Smith and Rutz 1991c). Fly breeding in this habitat is prolific, and natural populations of parasitoids, mostly Muscidifurax raptor (Girault & Sanders), do not become well established until 1-2 months after peaks in abundance of fly populations, which follow predictable seasonal patterns in the northeastern areas of the U.S. (Smith & Rutz 1991a). Producers often try to control the resulting fly infestations by making frequent applications of insecticides, but this approach aggravates insecticide resistance problems (Liu and Yue 2000) and may limit the development of robust populations of natural parasitoids and predators (Geden et al. 1992).

The decreased availability of new insecticides has generated problems for dairy cattle pest management by requiring the use of only a few pesticide active ingredients, which has resulted in high levels of pesticide resistance in pest populations (Rutz et al., 1994). More recently Kaufman et. al. (2001) reported high levels of house fly insecticide resistance from dairies across New York. Although the highest level of resistance was found with the contact insecticides permethrin, cyfluthrin and tetrachlorvinphos, resistance to methomyl (a bait formulation) was observed. Interest in biological control agents for the suppression of peridomestic muscoid flies on dairies is growing. Aware of the increasing cost of insecticides, decreasing availability of new chemicals and the development of insecticide resistance in resident fly populations (Scott et al. 1989), farmers are beginning to recognize the cost effectiveness of holistic integrated pest management strategies.

Surveys conducted around dairies in New York indicated the species that attacked housefly pupae were 59% M. raptor (Girault and Sanders), 14% Urolepis rufipes (Ashmead), 11% Phygadeuon fumator Gavenhorst, 10% Spalangia cameroni Perkins, 3% Spalangia nigroaenea Curtis, and 2% Trichomalopsis dubius (Ashmead) (Smith & Rutz. 1991b). Muscidifurax zaraptor (Kogan and Legner) and Muscidifurax raptorellus (Kogan and Legner) were relatively common in midwestern feedlots and dairies (Petersen et al. 1990, Petersen and Currey 1995). The abundance of parasitoids directly affects the parasitism rate of house fly pupae. For example, weekly releases of M. raptor resulted in a significantly higher rate of house fly parasitism, concurrent with a significant reduction in the house fly population compared to farms without releases of parasitoids (Smith and Rutz 1991b); such data would be beneficial in southern states. The parasitoids discussed are among the most important biological control agents for flies around dairies. Some species perform better in different climates and different agroecosystems as a result of different types of manure and other fly breeding materials. To specifically delineate optimal release rates through evaluation of parasitoid dispersal rate relative to established release rateswe used the red-eyed strain of Muscidifurax raptor in the North Carolina portion of the project.

The development of IPM approaches using waste management in conjunction with parasitoids release has shown potential to manage fly populations around dairies in the northeastern U.S. (Geden et al. 1992b, 1999). However, the success of this approach is dependent on knowledge of the species, the abundance of appropriate parasitoids in different areas of the country and identification of the primary control factors: this information is not available for Arkansas, North Carolina or Mississippi. Greene et al. (1989) has determined the species of parasitoids associated with dairies in Florida. Rutz and Axtell (1980) examined house fly parasitoids associated with poultry production in North Carolina and found eight pupal parasitoid species. Dry et al. (2007) studied the occurrence and seasonal distribution of house fly pupal parasitoids in northwest Arkansas poultry facilities.

Preliminary data on two family farms in Arkansas in 2000 indicated that the use of parasitoids coupled with restricted chemical use in an IPM program resulted in acceptable fly control (Pennington et al., 2001) and should result in less likelihood of adulteration of milk compared with the use of chemical methods of fly control. The use of parasitoids in these herds was comparable in costs to more conventional methods of fly control, allowing dairies to maintain a sustainable fly management system. In 2001 and 2002, the number of dairy farms utilizing parasitoids to control flies expanded to eight and six, respectively. The Arkansas Dairy Cooperative obtained a SARE producer grant to make additional producers and industry personnel aware of the benefits and limitations of using parasitoids for fly control on dairy farms. Also, these preliminary studies reinforced that proper manure management is necessary to control flies when utilizing parasitoids. Effective fly control also should help sustain the economic viability of these small- and medium-sized family dairies and the economic development of the rural economy in the area.

The sustainability of successful fly control around dairies in the southern areas of the United States is dependent on utilization of biological and cultural control (Rutz et al. 1994). The dependence on conventional insecticides must be reduced to avoid environmental risks and threats of pest resistance to the classes of insecticides that are currently effective. Relying on an integrated fly management approach, including biological control that is augmented with proper manure management, plus cultural and chemical controls to minimize pests will insure the long-term success of IPM programs and conserve insecticides. The natural parasitoids present on Arkansas, Mississippi and North Carolina dairies need to be evaluated to determine the most effective methods to incorporate these parameters into IPM programs, especially if they are not similar to commercially available parasites available to dairy producers. Effective waste management practices need to be studied to determine the system that best compliments the use of parasitoids in the control of house flies and stable flies around the dairy.

Cooperators

Click linked name(s) to expand
  • Sheri Brazil
  • Ricky Corder
  • Tanja McKay
  • Jodie Pennington
  • C. Dayton Steelman
  • Allen Szalanski
  • Karl VanDevender
  • Wes Watson
  • Scott Willard

Research

Materials and methods:

Participating farms in Arkansas, Mississippi and North Carolina cooperating in this project were typical mid-size family-operated production dairies. The number of lactating cattle at these dairies ranged from 60 to 140 plus replacement calves, dry cows and heifers. Facilities were typical for southern dairies and consisted of covered holding areas, feeding areas, calf barns and hutches and dry manure storage.

The seasonal distribution of naturally occurring pteromalid parasitoid wasps and percent parasitism was determined during 2005 prior to any releases and during 2006 and 2007 in control and “release” farms. In 2006 and 2007, commercially available pteromalid wasps were released at dairies in three states (AR, MS, and NC). Additional farms in each state served as a control with no releases. Weekly shipments of parasitoids were purchased to release ca. 200-250 per cow per week. Percent parasitism of house flies was monitored using sentinel bags (10 at each dairy), containing 30 house fly pupae each (Fig. 1). Sentinel bags were replaced weekly. Naturally occurring fly pupae were also collected each week. Pupae were placed in 96 well plates and sealed for ca. 8 wks and percent parasitism determined (Fig. 2). If neither parasitoids nor house flies emerged, pupae were dissected to identify developing parasitoids within the puparium. Weekly parasitoid shipments were sub-sampled and evaluated in a similar manner to that of sentinel pupae. After issues arose following low emergence of commercial parasitoids in 2006, 2007 methods were identical except that the 96 well plates were examined weekly to determine the number of emerged wasps while all other methods in 2007 remained the same as 2006. Sub-sample data was used to estimate the number of parasitoids released each week. All parasitoid wasps were identified to species using Gibson’s (2000) key (http://res2.agr.ca/ecorc/apss/chalkey/key into.htm).

In 2006, the appropriate numbers of parasitized house fly pupae were purchased to release approximately 200-250 parasitoids (a mixture of M. zaraptor and M. raptorellus) per cow at each farm receiving parasitoids. Sub-sampling data mentioned above was used to determine estimated numbers actually released which were much lower than the anticipated rate.

Because of low emergence rates of the commercially released parasitoids in 2006, the study was repeated in 2007. Methods for the 2007 study were basically identical to the 2006 study except additional farms were added to evaluate an additional parasitoid species, Trichomalopsis sarcophagae (Gahan). The appropriate numbers of parasitized house fly pupae were purchased to release approximately 200-250 parasitoids per cow at each farm. The additional farms received T. sarcophagae. Farms receiving the Muscidifurax mix in 2006 received the mix again in 2007. As in 2006, sub-sampling data were used to determine estimated numbers actually released. Numbers of the Muscidifurax mix were at the anticipated release rate. The actual number of Trichomalopsis released was greater than the anticipated release rate.

In 2006 and 2007, commercial parasitoid wasps were released weekly from May through October by placing parasitized house fly pupae on the farms. These releases were made in and near major filth fly breeding sites on the facility. These release sites included the manure storage area, holding areas, areas with spoiled feed and calf barns or hutches. Parasitized pupae were placed in areas protected from traffic, direct sunlight and water.

House fly abundance was monitored at each farm using sticky tapes that were replaced weekly from early April through October during 2005-2007. A minimum two ribbons per farm were placed in locations such as holding areas, calf barns or feeding areas. Flies were identified to species; however, the majority of flies collected were house flies.

Research results and discussion:

Species Composition: The two most abundant parasitoid genera collected from dairies in Arkansas, Mississippi, and North Carolina were Muscidifurax and Spalangia. Sub-samples of naturally occurring wasps identified as M. zaraptor, M. raptor and M. raptorellus were sent to the University of Arkansas PCR diagnostics lab which confirmed accuracy of identifications.

Data collected April through October, 2005, from sentinel house fly pupae indicated a 3.8% house fly parasitism rate, and a 17.2% parasitism rate in naturally occurring house fly and stable fly pupae averaged over all dairies (Table 1.). Species composition of parasitoid wasps determined through sentinel house fly pupae and naturally occurring house and stable fly pupae is presented in Figures 3 through 5. Twelve species of parasitoid were collected from Arkansas dairies (Fig. 3). The most prominent species collected from sentinel pupae was M. zaraptor. In contrast, Spalangia spp. was the most prominent found in naturally occurring pupae. Results were similar for Mississippi dairies in that a greater proportion of M. zaraptor was collected from sentinel than naturally occurring pupae (Fig. 4). However, Spalangia was the most prominent species in both sentinel and naturally occurring pupae in Mississippi dairies. Combined data from sentinel and naturally occurring pupae in Mississippi resulted in thirteen parasitoid wasp species. Results from North Carolina were more similar to Arkansas in terms of M. zaraptor and Spalangia proportions collected from the two methods (Fig. 5). A greater diversity of Spalangia species were found in North Carolina and Mississippi in comparison to Arkansas. In contrast to Mississippi and Arkansas, the greatest number of N. vitripennis was collected from North Carolina dairies. Of all three states, North Carolina dairies showed the greatest diversity of parasitoid wasp species. Combined data from sentinel and naturally occurring pupae in North Carolina revealed fifteen parasitoid wasp species.

In addition, Tetrastichomyia clisiocampe (Ashmead, 1894) (Eulophidae: Tetrastichinae), a gregarious species, was found from the Fultz farm in Arkansas. Previously, this species has only been recorded as a parasitoid of various families of Lepidoptera or as a hyperparasitoid of these through Tachinidae or Braconidae (Gary Gibson, Agriculture Canada, personal communication). This is the first record of it parasitizing a house fly puparium and also a new state record for Arkansas (Gary Gibson, Agriculture Canada, personal communication).

Baseline Parasitoid Abundance: Baseline data indicates that some farms have a greater abundance of naturally occurring parasitoids than others. Factors such as refuge for parasitoids and insecticide use contribute to species composition and abundance. Baseline parasitism prior to release of parasitoids and at control farms varied. Parasitism rates were generally higher from naturally occurring pupae (M. domestica, S. calcitrans and Family Calliphoridae) than from sentinel house fly pupae. The overall seasonal average parasitism rates from naturally occurring pupae was 17.2% and ranged from 2.9 for an Arkansas dairy to 31.1% for a North Carolina dairy. In contrast, the overall seasonal average parasitism from sentinel house fly pupae was 3.8% and ranged from 2.9% for North Carolina to 19.6% for a Mississippi dairy (Table 1).

Quality assessment and sub-sampling: A quality assessment summary of sub-samples from commercial parasitoid shipments released in southern dairies is presented in Table 2. A mix of M. zaraptor and M. raptorellus were purchased for 2006 studies. However, sub-sampling revealed that N. vitripennis, a contaminant, and M. zaraptor were actually released. Only a small fraction of the wasps were M. raptorellus. When comparing the actual number of wasps released to our target rate, Arkansas farms (CA AR and FZ AR) were close to the target rate; however, the majority of the wasps were N. vitripennis that presumably contaminated the M. raptorellus colony. Most authorities consider N. vitripennis less desirable for releases because of poor dispersal and lower parasitism rates. Sub-sampling from the Mississippi farm (MR MS) showed that the actual release was only about 17% of the target release even if N. vitripennis is included in that number.

Assessments from 2007 sub-samples of commercial parasitoid shipments were encouraging (Table 2). In 2007, a mix of the solitary M. zaraptor and gregarious M. raptorellus were purchased for 4 farms and the gregarious T. sarcophagae for 3 farms. With the exception of the Mississippi (MR MS), the M. zaraptor and M. raptorellus mix was much closer to the target release number than in 2006 (Fig 6-12). Also, no N. vitripennis were recovered from any 2007 sub-samples (Table 2). The actual release number for T. sarcophagae was roughly 4 times greater than the target release number.

Approximately 54 to 62% of the emerged wasps from all species were female. Also, roughly 4.7, 8.5 and 7.0 of emerged M. raptorellus, T. sarcophagae and N. vitripennis were produced from each parasitized pupae, respectively.

Although percent emergence of commercial parasitoids sub-sampled in 2007 was improved in comparison to 2006, this emergence occurred over a 2-3 week period instead of within 3-5 days. Only about one-fourth Muscidifurax mix wasps emerged within 7 days of receipt when held at room temperature. When held outdoors at temperatures simulating those in dairies, roughly 43% emerged within 7 days of receipt. For T. sarcophagae, the percentage of wasps emerging from sub-samples within 7 days of receipt were 48 and 58 % for those held at room and at outdoor temperatures, respectively (Table 3). With weekly releases, producers expect the majority of parasitoid wasps to emerge before the next shipment is received and released.

Sub-sampling data indicated that quality control can be an important issue for producers using commercial parasitoids in their fly control program. When purchasing parasitoid wasps for use in their fly IPM program, producers are encouraged to include quality assessment. Arkansas dairy producers, involved in 2007 and 2008 demonstrations, incorporated parasitoid quality assessment into their programs.

Parasitism rates following releases: Significant increases in percent parasitism for farms receiving parasitoids were not noted. The seasonal parasitism of sentinel house fly pupae across all farms receiving parasitoids was about 12.1% compared to 9.8 % for control farms in 2006 (Table 4). Only a fraction of the parasitoids released in 2006 were of the desired Muscidifurax mix. Studies were continued in 2007 to determine if higher parasitism rates would occur if the desired species and quantity were actually released. Despite releasing the desired species and quantity in 2007, overall differences in parasitism did not occur. Overall parasitism rates across all farms were 8.75, 4.3 and 6.5% for the control, T. sarcophagae and Muscidifurax mix (M. zaraptor and raptorellus) farms, respectively (Table 5). Although parasitism rates from naturally collected pupae were higher than from sentinel house fly pupae, trends in parasitism of the control and release farms were similar (Table 6 & 7).

In addition to percent parasitism, potential parasitoid induced mortality was tracked throughout the study. Parasitoid induced mortality occurs when a parasitoid probes a fly pupa but only stings the pupa and does not oviposit eggs. Intact pupae with no emergence of adult house flies or parasitoids were dissected, if no immature parasitoids were present and no signs of damage were visible, they could be considered the result of parasitoid induced mortality. In 2006, potential parasitoid induced mortality in sentinel house fly pupae was virtually the same across all control and release farms at 17.2 and 15.6%, respectively (Table 4 & 6). In 2007 data, potential parasitoid induced mortality was somewhat higher across all farms receiving T. sarcophagae (19.2%) compared to the control (12.6%) and Muscidifurax mix (11.7%) (Table 5 & 7).

House Fly Abundance: House fly abundance is summarized in Table 8. Monthly average house flies per strip varied from farm to farm (from below 100 per flies per week to a high over 500 per strip per week). Combined data from 2006 comparing fly abundance in release verses control farms were similar demonstrating little differences between control and release farms. Some individual farms (control and Muscidifurax mix release) demonstrated consistently low to moderate fly numbers (<100 to 150) while others (again both control and Muscidifurax mix release) consistently had high numbers (>150 to over 700 per strip per week). Fly abundance data from 2007 was similar to 2006, with combined monthly averages of control, Muscidifurax mix release and T. sarcophagae being very similar in combined monthly average flies per strip per week ranging from 90 to 292. Weekly graphs of house fly abundance by week for each state is provided in the appendix.

Participation Summary

Educational & Outreach Activities

Participation Summary

Education/outreach description:

Dairy production meetings to update producers and focus team members on progress and recommendations related to fly IPM were held throughout the course of this project (See outreach listing). This outreach included presentations, demonstrations, field days, newsletters and production meetings. Final workshops/field days and in-service training for agents were combined and provided during 2008. To increase producer and agent participation by reducing travel time and expenses, these workshops were provided in the four major milk producing regions of Arkansas. These workshops included power point presentations, handouts, portable sanitation/parasitoid impact demonstrations, microscopic viewing of fly pests and parasitoid wasps, demonstration of monitoring, trapping and compatible insecticide use and tour of the dairy facilities. A similar workshop was held in North Carolina. Other outreach includes the production of an educational video, a fact sheet (Fly Control for Organic Dairies), an online multimedia in-service training module for county agents which has been modified to be included on eXtension and the Southeast Dairy Extension websites (see CD Rom). Postings on these sites provide outreach opportunities to Extension educators and dairy producers in other states.

Throughout the course of this project, progress has been reported at professional conferences (see outreach listing). Venues included Entomological Society of America annual meetings, the Livestock Insect Workers Conference, the Arkansas Entomological Society and the Southern Dairy Conferences. Final presentations were given at the 2008 Entomological Society of America’s Annual Meeting and the 2009 Southern Conference. Extension activities and results have also been included in S-1030 (Flies Impacting Livestock Poultry and Food Safety) annual reports. Two manuscripts (one detailing species composition of pteromalid parasitoids in southern dairies and the other related to quality of commercial parasitoids) are in preparation for submission to an entomological journal.

Project Outcomes

Project outcomes:

Comprehensive baseline data on the species composition and abundance of pupal filth fly parasitoids found in southern dairy ecosystems was lacking prior to this project. Project results provided beneficial information that can be used for future work in identifying other candidate species for rearing and release. Results also demonstrated that individual dairies have moderate levels of parasitism without augmented releases and could be preserved through specific management techniques such as judicious use of insecticide (use of “natural enemy” compatible insecticides) and maintenance of limited refuge for preservation of the parasitoids present.

One dramatic outcome of this project was the identification of deficiencies in use of parasitoids as an IPM approach to manage filth flies. The most important deficiency is quality assurance in commercial parasitoid production. Sub-sampling data from 2006 revealed much lower than anticipated emergence of wasps and contamination with a less desirable parasitoid species (N. vitripennis). Sub-sampling results from 2007 were encouraging in that wasp emergence was sufficient to assure the release of the target number of adult wasps. However, this emergence occurred over a two week interval rather than a three to seven day period, which could allow additional time for predators to consume the immature parasitoid before adult wasps emerge. Deficiencies in quality control identified areas for additional work to improve the effectiveness of parasitoid wasp releases for use in fly IPM.

As a result of quality control issues, producers participating in fly IPM demonstrations were trained in methods to monitor and estimate commercial parasitoid quality in terms of emergence and emergence interval. Most demonstration participants indicated that this sub-sampling was worth the additional time investment. Demonstration participants and field day/dairy IPM meeting participants were also trained in other aspects of fly IPM on dairies such as monitoring methods, compatible insecticide use, trapping methods, fly identification and sanitation. Regardless of whether parasitoids are used in fly IPM programs or not, organic and conventional producers benefit from this training and outreach material. Fly IPM training material resulting from this project is available to producers, county agents and other professionals involved in fly IPM. Outreach and outreach material is described below.

Economic Analysis

None proposed.

Farmer Adoption

Evaluation: Cooperating dairies involved in demonstrations were asked to complete a questionnaire to ascertain producer views of the fly IPM program. Briefly, of the 6 cooperators using parasitoid wasps, trapping, enhanced sanitation and monitoring, the majority (5) were pleased with the program. All agreed that the effort expended was worth the extra time commitment. Most (5) also noted that the cost were comparable to conventional control methods and noted a difference in fly control (see evaluation material).

In the fall of 2008, an IPM questionnaire was sent to all Arkansas dairy producers to determine the level of IPM adoption and ranking of pest concerns. Of 145 dairies, questionnaires were returned by 57 dairies (39% response). Results from the survey were encouraging. Over 97 % of respondents indicated that they use more than one method to control house flies. About 65% of respondents indicated that they used sticky ribbons and tapes and traps to monitor house flies, however, only about 5% used fly counts as a method to determine the need for fly control. Eighty-five percent of respondents used the simple presence of house flies as a basis to initiate fly control with the remaining 12% conducting scheduled treatment to manage house flies. Highlights of the summary are available (see evaluation material).

Recommendations:

Areas needing additional study

Although parasitoid emergence from commercial parasitoid sub-samples was much improved in 2007 compared to 2006, parasitoids emerged over a 2 to 3 week period regardless of whether held in the lab or outdoors (at conditions similar to release sites (dairies)). It was not uncommon for 50% or fewer to emerge during the first week, with a large percentage emerging after a week. Extended emergence of field released parasitoid parasitized house fly pupae may increase predation on these house fly pupae and decrease the effectiveness of parasitoid releases.

In addition to these observations, recovery of sentinel house fly pupae from Mississippi was much lower than in Arkansas or North Carolina dairies. Often the sentinel bag from Mississippi would be near or completely empty of intact house fly pupae suggesting higher predation rates. This observation leads one to ask if increased predation occurs in parasitoid parasitized house fly pupae. One potentially important predator present in Mississippi but currently absent in the cooperating dairies in North Carolina and Arkansas is the red imported fire ant, Solenopsis invicta.

These observations and findings resulting from this project suggest areas the following areas for further study.

1. If parasitoid emergence occurs over a 2-3 week period of time, will “protected” release stations increase the number of actual wasps that can parasitize house fly pupae? Further studies aimed at optimizing distance and placement of release stations are needed.

2. Can efficacy of parasitoid wasp releases (through increased survival, etc.) be enhanced with placement of nutrient/energy sources for the newly emerged parasitoid wasps?

3. In southern regions with pests such as imported fire ants, to what extent are parasitized house fly pupae (releases) destroyed or consumed by predators. An extended emergence period (of released parasitized pupae) could increase the predation rate. Studies aimed at determining if these predators exhibit a preference for parasitized or non-parasitized house fly pupae are needed.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.