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

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

Summary

During 2007 filth fly parasitism and house fly abundance after releasing parasitic wasps was evaluated in Arkansas, Mississippi and North Carolina dairies to incorporate this technology into filth fly IPM. These 2007 releases, representing an additional year of field studies, were conducted because of quality assurance issues with commercial parasites encountered during 2006 field studies. In 2006 and 2007 baseline data collected in 2005 was used to establish timing and rates of parasite releases. Quality assurance issues with commercial parasitoids encountered during 2006 resulted in implementing additional quality assessment techniques in 2007 to monitor quality and survival during shipping.

During 2007 and early 2008, results from this project as well as general IPM recommendations were presented to focus teams, dairy in-service trainings, dairy field days, professional meetings, and production meetings (including organic dairy meetings). Fly IPM demonstrations were conducted in 2007 that included both organic and conventional dairies. In addition, producers participating in 2007 demonstrations were surveyed to determine their acceptance of fly IPM methods.

Objectives/Performance Targets

The overall purpose of this project is to develop a biologically based IPM program to manage house and stable flies on small and medium sized dairies. Studies during 2007 evaluated parasitoid impact and level of filth fly pupal parasitism after wasps were released on Arkansas, Mississippi and North Carolina dairies. A newly available species, Trichomalopsis sarcophagae, was evaluated in 2007 to determine the efficacy of this species in the southern United States. Also, several demonstrations were conducted in 2007 on both conventional and organic dairies using the parasitoid releases. Parasitoids of both house and stable flies prevent parasitized fly pupae from emerging into adult flies. The project involves other IPM techniques such as manure management and judicious use of insecticide that is compatible with natural enemies such as pteromalid wasps.

The major research objective for 2006 and 2007 was to evaluate the level of filth fly pupal parasitism after wasp releases on Arkansas, Mississippi and North Carolina dairies. Study locations selected in 2004 were used during the 2007 fly season to collect data on parasitism levels. However, two locations in Central Arkansas were not used during 2007, but an additional farm in Northwest Arkansas and one in North Carolina were added. Rates and timing determined from baseline data collected in 2005 were used during 2007 studies. Dairies not receiving commercial parasites served as a control and were evaluated for natural parasitism in order to build upon data collected in 2005 and 2006.

Another objective initiated in 2004 and expanded in 2007 was the formation of focus teams to assist in development of outreach. Two teams of entomology and animal science specialists, county agriculture agents and dairy producers have been formed in the two major milk producing areas of Arkansas. These teams have now met numerous times and provided valuable insight into the most promising venue to reach dairy producers. They have also provided feedback related to IPM concerns (insecticide resistance in horn flies, insecticide labeling issues, and sanitation). During 2007, focus teams helped guide investigators in production of the extension outreach component of the project. Fact sheet material and an educational video available on DVD are included in the outreach component that will be primarily electronic.

Data collected for dairies in 2005 was used to determine the release rates and timing of commercial pteromalid wasp releases made during the 2007 fly season. The overall IPM concept was incorporated with commercial wasp releases. These IPM techniques included population monitoring of fly pest species, establishment and use of treatment thresholds, limited use of insecticides that are compatible with natural enemies, and effective manure and waste management. Outreach components (video, additional fact sheets and final dairy field day/in-service training) of the project will be finalized during the remainder of 2008.

During 2007 sentinel house fly pupae and naturally occurring house and stable fly pupae were placed and/or collected from cooperating dairies selected in 2004 with the addition of two dairies and the exclusion of 2 dairies (Arkansas (3 dairies), Mississippi (2 dairies) and North Carolina (5 dairies)). The farms discussed in this report are labeled as follows: FZ (Muscidifurax zaraptor and M. raptorellus mix release), UR (Trichomalopsis sarcophagae release), and CH (control) in Arkansas; MR (M. zaraptor and M. raptorellus mix release) and MSU (control) in Mississippi; JL (T. sarcophagae release), PT (T. sarcophagae release), LW (M. zaraptor and M. raptorellus mix release), MN (M. zaraptor and M. raptorellus release), and NL (control) in North Carolina. All of the 2005 data and 2006 data are completed. Much of the 2007 data have been analyzed, however wasp species are still being identified for sentinel and naturally occurring pupae.

During the 2006 study, the number of parasitic wasps (as parasitized house fly pupae) to release 200-250 wasps per cow per week were purchased. Parasitized house fly pupae were obtained from a reputable insectary. However, the results from sub samples of each commercial parasitoid shipment revealed a lower percentage of parasitism and emergence than anticipated. Also, a “contaminant” species of wasp, Nasonia vitripennis, was found in most of the subsamples. This species is gregarious and once it becomes established in a colony, it often eventually replaces Muscidifurax raptorellus. N. vitripennis should be avoided when releasing wasps due to their low parasitism rate. This problem was not discovered until after all releases had been made because wasps had not been identified until the field season was over. Due to these problems, the emphasis on quality, and the need for quicker sub-sampling methods became evident. In 2007, we continued research on the dairies in order to gain additional data at the release rate we initially planned. Discussions were made with the insectary’s representative to remedy the situation. In order to determine where problems were occurring (shipping, etc.), sub samples were taken at the insectary prior to shipment and upon receipt. This allowed for early detection of any potential problems. During 2007, a newly available species of parasitoid, Trichomalopsis sarcophagae, was released in addition to Muscidifurax zaraptor and M. raptorellus. Trichomalopsis sarcophagae, a gregarious species that would be less expensive to mass rear, needed to be evaluated to determine it’s potential in filth fly IPM in the southern United States. T. sarcophagae was released at one farm in Arkansas and two farms in North Carolina. Muscidifurax zaraptor and M. raptorellus were released at one farm in Arkansas, two farms in North Carolina, and one farm in Mississippi.

The estimated number of parasitized house fly pupae, average percent parasitism, estimated number of parasitized pupae released, average percent of pupae that had parasitoids emerge and the estimated total number of pupae released with parasitoid emergence for farms, CA, FZ and MR during 2006 are shown in Table 1 (contact SARE for copy of tables). Table 2 (contact SARE for copy of tables) shows the average proportion of parasitoid species received and average number of individuals of Nasonia vitripennis per house fly pupae received for farms, CA, FZ and MR in 2006. The total number of parasitoids released at farms, CA, FZ and MR during 2006 is shown in Table 3 (contact SARE for copy of tables). The average percent emergence for farm CA was close to the expected percent emergence of 70%; however 83% of the parasitoids that were released at this farm were N. vitripennis. Most of the wasps released at farm FZ were also the contaminant species with 89% of the individuals being N. vitripennis. For the farm MR, 81% of the individuals released were N. vitripennis. Some M. zaraptor were released at each of these farms, but very few M. raptorellus were released with farm MR having zero M. raptorellus released.

The estimated number of parasitized house fly pupae, average percent parasitism, estimated number of parasitized pupae released, average percent of pupae that had parasitoids emerge and the estimated total number of pupae released with parasitoid emergence for farms, UR, FZ, MR, MN, LW, JL and PT during 2007 are shown in Table 4 (contact SARE for copy of tables). Table 5 (contact SARE for copy of tables) shows the average proportion of parasitoid species from house fly pupae received for all seven farms in 2007. The total number of parasitoids released at the farms during 2007 is shown in Table 6 (contact SARE for copy of tables). Farms UR, JL and PT all received T. sarcophagae wasps. Sub-sampling of T. sarcophagae revealed a lower percent emergence rate than the target of 70%. However, the lower percent emergence was more than offset in sheer numbers because T. sarcophagae is a gregarious species. More T. sarcophagae were released at all three farms than was anticipated. Farms FZ, MN and LW received Muscidifurax zaraptor and M. raptorellus. They exhibited a good average emergence with the percent emergence rate being above 70%. M. raptorellus is also a gregarious species, however M. zaraptor is solitary. The total number of parasitoids released at these three farms was not as high as the T. sarcophagae releases. Farm MR had a very low average percent emergence rate of 26%.

Figure 1 (contact SARE for copy) shows the percent emergence of parasitoids from sub sample pupae each week at Arkansas farms, UR (T. sarcophagae) and FZ (Muscidifurax zaraptor and M. raptorellus) during June to September, 2007. The percent emergence for UR ranges from 24 to 100%. FZ has a range of 69-98% emergence. An expected percent emergence of 70% would be considered good for all species. Figures 2 and 3 (contact SARE for copy) show the estimated number of individual wasps released weekly at Arkansas farm, UR (T. sarcophagae), and the estimated number of individual wasps released at Arkansas farm, FZ (M. zaraptor and M. raptorellus), respectively. UR ranged from 24,784 to 267,017 wasps released weekly. During the week in which 267,017 wasps were released, the insectary was anticipating a bad shipment for that week and supplied two bags of parasitized pupae therefore increasing the release amount. The expected number of wasps released each week was 30,000 according to the release rate being evaluated. The number of wasps released weekly at FZ ranged from 18,423 to 62,119. The expected number of wasps released each week was 25,000 according to the release rate being evaluated.

Figure 4 (contact SARE for copy) shows the percent emergence of parasitoids from sub sample pupae each week at Mississippi farm, MR (Muscidifurax zaraptor and M. raptorellus) during June to October, 2007. The percent emergence ranges from 8 to 38% for farm MR. The wasps received should have an emergence rate of approximately 70%, and the rate for MR was considerably lower this year. Figure 5 (contact SARE for copy) shows the estimated number of individual wasps released at farm MR. The number of individuals released ranged from 3,755 to 25,549, and the expected number of wasps released each week was 30,000 according to the release rate being evaluated.

The percent emergence of parasitoids from sub sample pupae each week at North Carolina farms, JL (Trichomalopsis sarcophagae), PT (T. sarcophagae), LW (Muscidifurax zaraptor and M. raptorellus) and MN (M. zaraptor and M. raptorellus), during July to September, 2007 is shown in Figure 6 (contact SARE for copy). The percent emergence ranges from 15 to 84% for JL, 13 to 88% for PT, 53 to 98% for LW, and 45 to 95% for MN. The expected percent emergence rate for the wasps received and released at all farms was 70%. The estimated number of individual wasps released for each of the farms is shown in Figures 7-10 (contact SARE for copy). The number of wasps released weekly at JL ranged from 29,745 to 262,397 with the expected number of wasps released each week to be approximately 40,000. The expected number of wasps to be released each week at farm PT was also 40,000, and the number of individuals released weekly ranged from 33,712 to 221,773. The number of wasps released weekly at LW ranged from 32,494 to 60,270 with the expected number to be released at 30,000 per week. The expected number of wasps to be released at farm MN was also 30,000 per week, and the numbers ranged from 22,570 to 65,051 wasps released weekly.

Each farm’s total percent parasitism for both sentinel and naturally occurring pupae are shown by Table 7 for all farms in 2006 (contact SARE for copy of tables). During 2006 the overall percent parasitism in sentinel pupae was 9.7% and 17.1% for naturally occurring pupae. The increase of 5.9% parasitism in sentinel pupae from 2005 to 2006 was encouraging despite the low emergence rate and contaminant species that we encountered. No naturally occurring pupae were collected in 2006 from farms FZ and CH.

Table 8 (contact SARE for copy) shows the number and prevalence of parasitoids reared from sentinel Musca domestica pupae on ten farms during May to October, 2006. Muscidifurax zaraptor parasitized the greatest number of sentinel pupae with 39.3% of the total number parasitized. The number and prevalence of parasitoids collected from naturally occurring pupae of Musca domestica, Stomoxys calcitrans and blow flies (Family Calliphoridae) at eight of the farms during May to October, 2006 is shown in Table 9 (contact SARE for copy). The greatest percent of naturally occurring pupae were parasitized by Spalangia cameroni with 16.7% of the total number parasitized. No naturally occurring pupae were collected in 2006 from farms FZ and CH. Table 10 (contact SARE for copy) shows the number of parasitoids collected from sentinel Musca domestica pupae each month from May to October, 2006 for all farms. The greatest number of parasitoids was collected during the month of June with a total of 1,083 parasitoids. The number of parasitoids collected from naturally occurring pupae of Musca domestica, Stomoxys calcitrans and blow flies (Family Calliphoridae) each month from May to October, 2006 for eight farms is shown in Table 11 (contact SARE for copy). A total of 330 parasitoids were collected in June, which was the month that the greatest number of parasitoids was collected. No naturally occurring pupae were collected in 2006 from farms FZ and CH.

The total percent parasitism for sentinel pupae on each farm during 2006 is shown in Table 12 (contact SARE for copy). During 2005 data was collected prior to parasitoid releases at farms in Arkansas and Mississippi. The percent sentinel Musca domestica pupal parasitism increased for release farms CA, FZ and MR from 2005 to 2006 when releases were made. However, North Carolina farms, JL, LW and MN, received wasp releases during 2005 as well as 2006. The percent parasitism of these farms during 2005 was 5.91% at JL, 2.54% at LW and 3.62% at MN. The control farm, NL, had 2.65% parasitism during 2005. The 2006 sentinel data resulted in a percent parasitism of 5.30%, 11.34%, and 8.01%, at the JL, LW and MN farms, respectively. The percent parasitism for the control farm, NL, was 9.77%.

In the parasitoid dispersal study two of the North Carolina release farms had a slightly greater percent parasitism than the control farm; however one farm was slightly lower in percent parasitism than the control. The sentinel percent parasitism at farm JL slightly decreased from 2005 to 2006. There was an 8.8% increase in 2006 for farm LW, and a 4.39% increase in 2006 for farm MN. Control farm, NL also had an increase from 2005 to 2006 of 7.12%.

The total percent parasitism for naturally occurring pupae on each farm for 2006 is shown in Table 13 (contact SARE for copy). Pre-release data was collected in 2005 of parasitoids at farms in Arkansas and Mississippi. The percent parasitism of naturally occurring pupae increased for release farms CA and MR from 2005 to 2006 when releases were made. No data was collected for farm FZ during 2006. North Carolina farms, JL, LW, and MN, received wasp releases during 2005 as well as 2006. The percent parasitism of naturally occurring pupae at these farms during 2005 was 24.95% at JL, 23.13% at LW and 27.67% at MN. NL, the control farm, had 31.15% parasitism during 2005. The 2006 naturally occurring data resulted in a percent parasitism of 19.53%, 20.03%, and 18.84%, for the JL, LW and MN farms, respectively. The percent parasitism for the control farm, NL, was 27.01%.

The control farm in North Carolina had a greater percentage of parasitism in naturally occurring pupae than the release farms in 2005 and 2006, and all North Carolina farms decreased in percent parasitism in 2006. Farm JL slightly decreased by 5.42%, farm LW decreased by 3.1%, and farm MN decreased by 8.83%. Control farm, NL also decreased in 2006 by 4.14%.

Figures 11 and 12 show the percent parasitism of sentinel and naturally occurring pupae for each farm during 2006 (contact SARE for copy). Pupal parasitism occurred throughout the fly season with the least amount of sentinel parasitism occurring early and in some farms late in the fly season. The least amount of parasitism of naturally occurring pupae occurred early in the season with the greatest parasitism at some farms being later in the season. Readers interested in studying changes in parasitism rates through the season may contact SARE to obtain a copy of these figures.

Results from 2006 naturally occurring pupae and sentinel Musca domestica pupae indicate that similarities of species composition exist within differing geographical areas of the southern states. Data also show that differing methods (i.e. sentinel versus naturally collected pupae) may result in differing species composition and abundance indicating that use of both methods will provide more reliable baseline data. Among the most abundant species occurring on southern dairy farms were Muscidifurax zaraptor and Spalangia cameroni. This indicates that these species are suitable candidates for wasp releases. Figures 13 through 18 (contact SARE for copy) provide detailed information on the species composition and relative abundance of pteromalid wasps collected from dairies in Arkansas, Mississippi and North Carolina.

House fly (Musca domestica) abundance at two Arkansas farms during 2005, 2006 and 2007 is provided in Figures 19 and 20 (contact SARE for copy). In Figure 20 (contact SARE for copy), these two Arkansas farms are represented as well as an additional farm used for Trichomalopsis sarcophagae release in 2007. House fly seasonal abundance decreased in 2006 for both the control farm CH and the release farm FZ. In 2007, control farm CH had higher fly numbers than the two release farms until the end of the season where all three farms were similar in abundance. Farm UR, which received T. sarcophagae wasp releases had lower numbers towards the end of the season as compared with farm FZ, which received Muscidifurax zaraptor and M. raptorellus wasps. The two release farms were similar in house fly abundance for the first half of the season.

Figures 22 – 24 (contact SARE for copy) represent the house fly (Musca domestica) abundance at two Mississippi farms during 2005, 2006 and 2007. During 2005, the fly numbers for farm MR were higher than farm MSU. In 2006, Muscidifurax zaraptor and M. raptorellus wasps were released at farm MR and MSU was used as the control. The fly numbers at both farms decreased throughout the season, but numbers at MR were consistently higher than the control farm MSU. Fly numbers during 2007 were similar to the numbers during 2005 in that numbers at release farm MR were higher than the numbers at control farm MSU.

North Carolina house fly (Musca domestica) abundance during 2006 and 2007 is shown in Figures 25 and 26 (contact SARE for copy). Farms MN, LW and JL received Muscidifurax zaraptor and M. raptorellus releases during 2006. Farm NL was used as a control. All four farms had low numbers and followed a similar trend in 2006 with a peak in fly numbers during midsummer. The control farm had slightly higher numbers during the first half and at the very end of the season. During 2007, farms MN and LW received M. zaraptor and M. raptorellus. Farm PT was added in 2007, and this farm along with farm JL had Trichomalopsis sarcophagae wasps released. Farm NL was again used as a control. Farm MN had higher numbers of fly abundance throughout the fly season. Farm JL had several peaks that were higher than the other farms. Farms NL, LW, JL and PT had relatively low fly numbers (below 100) during the second half of the fly season.

Principal investigators from Mississippi, North Carolina and Arkansas communicate frequently through telephone and email in addition to yearly meetings. During 2007 focus team meetings were held in conjunction with organic dairy “kitchen” meetings, field days and conventional dairy production meetings.

Accomplishments/Milestones

Data on the species composition and abundance of naturally occurring parasitoids was collected again during the 2007 fly season. This data provided valuable information that will add to the data collected from 2005 and 2006 in order to help provide recommendations concerning fly IPM for southern dairies. Commercial parasitic wasp releases were made in 2007 and compared to control farms and to the previous years. The preliminary data provided in this report are mixed (increased percent parasitism and decreased fly abundance on some “release” farms).

Two focus teams consisting of entomology and animal science specialists, county agriculture agents and dairy producers were formed in the two major milk producing areas of Arkansas in 2005. These groups met various times during 2007. These teams continue to meet during field days and kitchen meeting and have provided valuable insight into the most promising venue to reach dairy producers. Their input and feedback will guide much of the major dairy/IPM outreach component of the study scheduled for 2008.

IPM demonstrations directly related to this project as well as projects for managing other pests such as horn flies were conducted on seven Arkansas dairies during 2007. Producers were taught how to effectively sub-sample commercial parasitoid shipments in order to assure quality control of wasps they would receive. The producers were given data sheets to record the number of parasitoid wasps present at 3 days, 1 week and 2 weeks after placing approximately 50 to 100 parasitized pupae into a glass jar or similar container. This allowed for observance of emergence rate and detection of problems as they arose. Producers were also taught how and where to release the wasps throughout their dairy facility. The counting of house fly numbers on fly strips was also shown to producers and data sheets were provided so they could record the numbers each week. After analyzing the data from the demonstrations, overestimation of house flies on the strips by some producers was evident. This emphasizes the fact that proper fly identification needs to be addressed more thoroughly to producers. Producers were also taught how to make horn and stable fly counts on the cows. Again, data sheets were provided for them to record this data weekly. At the end of the demonstrations, surveys were given to each producer that participated. The overall consensus of the project was that the producers were pleased with the project and thought additional effort was worth their time. Overall, the producers encountered no technical problems with the techniques (other than fly identification and population estimation), indicated that they did see a difference in fly control when using these techniques and that the IPM methods were comparable in cost to traditional insecticide usage.

Impacts and Contributions/Outcomes

Results from this project as well as general dairy IPM recommendations have been presented in numerous venues during 2007 and the first part of 2008 (yearly dairy field day, organic production meetings, demonstrations in organic dairy, meeting with organic dairy certifier, as well as professional meetings (Arkansas Entomological Society, Livestock Meeting, Entomological Society of America and Southern Dairy Conference)). Additional presentations have and will be made during the remainder of 2008. Educational outreach materials have been created through input from the focus teams. A fact sheet entitled “Fly Control for Organic Dairies” was created and made available on the University of Arkansas Cooperative Extension Service website. A fly IPM video has been created, but still needs to be finalized after input from collaborators.

Also an interest in dairy/fly IPM using parasitoids has increased as a result of local interest in organic milk production. Producers express interest in using IPM and parasitoids as a means of reducing pesticide usage to comply with the organic production guidelines. More fly IPM demonstrations are planned in 2008.

Data from the past three years has shown producers the importance of sanitation in any fly management program. One very important outcome from this study has been the importance of quality assurance and selecting the appropriate species for release. Development of an assessment method that producers can easily employ to determine percent emergence of commercial parasitoid shipments was successful during 2007 demonstrations. Focus team members were shown that house fly numbers from sticky ribbons were much higher on farms that had an abundance of fly breeding material. This helped illustrate that sanitation is the most important component in managing house flies in animal or milk production systems and that any management system used must incorporate sound sanitation practices. Data from 2006 parasitoid shipment sub-sampling indicated the importance of parasite quality and the need to develop a producer friendly procedure for assessing parasitoid emergence/quality. In 2007, an assessment method that producers can easily employ to determine percent emergence of commercial parasitoid shipments was developed. This procedure was adopted and well received by producers in 2007 and is currently being used by some dairy producers in 2008.

Collaborators: