Development of best use practices on commercial colonies of Bombus impatiens on crops in Delaware

Final Report for ONE12-157

Project Type: Partnership
Funds awarded in 2012: $5,696.00
Projected End Date: 12/31/2013
Region: Northeast
State: Delaware
Project Leader:
Dr. Deborah Delaney
University of Delaware
Co-Leaders:
Jacquelyn Marchese
University of Delaware
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Project Information

Summary:

To help combat pollinator shortages, mainly those of honey bees, and meet the pollination requirements of important agriculture crops, researchers with four commercial growers investigated the effectiveness of a native pollinator in Delaware, the Common Eastern Bumble Bee (Bombus impatiens). Bumble bee colony growth was measured over the season in three different crops: strawberry, watermelon and pickling cucumber. Colony placement effects were examined, and overall bumble bee health, foraging activity, colony weight and survival were assessed and compared among colonies with different nest placements (artificial shade versus natural shade versus sun). The yield and quality of harvested crops in fields where bumble bees were placed was also measured. We found that colonies placed in the shade foraged more, weighed more and had a longer survivability and arrival to peak forage date than those colonies placed in the sun. We also found that colonies placed in the sun had larger brood clumps or amounts of cells during the post mortem analysis. Placing colonies in the sun had adverse effects on the bumble bee’s ability to thermoregulate the nest as evidenced by the reduction in foraging activity and weight gain most likely due to a decrease in energy supplied to rearing more workers. From this work we have arrived at 10 BMPs for farmers regarding the use of these pollinators in larger field settings:

1. Bumble bees can be used for strawberry and watermelon but not for pickling cucumber horticultural crops.
2. Place bumble bees in the field after crops have begun to bloom.
3. Allow time for bees to settle before opening units.
4. Close bumble bee units before each pesticide application.
5. Dispose of bumble bee colonies in a timely and humane fashion.
6. Bumble bees can be placed in the middle or on the edge of the field.
7. Place bumble bees under shade, to increase productivity and longevity of the bumble bees.
8. Keep bumble bees away from honey bees.
9. Strap down bumble bee units.
10. Bumble bee units may successfully be transferred to another field.

Introduction:

Each year, in the state of Delaware, over four thousand acres of cucumbers are planted and harvested valued at 4.5 million dollars, roughly three thousand acres of watermelon are planted and harvested valued at over 10 million dollars and strawberries alone bring close to a half a million dollars into the state (Delaware Reports and Statistics, 2007-2008). All of these crops rely upon pollination services provided by insects. The ‘western’ honeybee (Apis mellifera) is arguably the most economically valuable pollinator of agricultural crops worldwide (Robinson et al. 1989, Free 1993), and the most widely used and economically important managed pollinator in Delaware.

The annual, economic value of the honey bee in Delaware is estimated at approximately $15 million with an annual, nation-wide value of $14.6 billion (Morse, Calderone, 2000). Unfortunately, honey bee populations have been declining over the past decade due to their susceptibility to numerous pests and pathogens which has had profound negative effects on their ability to over winter and therefore build up populations in the spring when many crops start to bloom (vanEngelsdorp et al. 2007, 2008). This decrease in managed pollinator populations during the blooming period of important crops has growers and pollination ecologists concerned and looking to alternative, native pollinators.

Grower’s interests are on the rise in utilizing this native pollinator and many growers are starting to use bumble bees units in their fields. Koppert Biological Systems© is one of the main suppliers of pollination units in the United States. Their web page (www.koppert.com) provides guidelines and usage tips for different fruit and vegetable crops. The colony life expectancy for these units depends on the crop and ranges from 6-12 weeks, but many growers in Delaware are reporting that colony growth and activity among the units is highly variable and often times short lived. Although many growers are finding these units an appealing alternative to honey bee colony rental, due to the ease of movement and the superior pollen transfer service they provide, they want to know what the economic benefits are in using bumble bees over honey bees. Additionally, questions and problems are starting to surface about how to keep these pollination units active through the whole bloom period.

The behavior, physiology and morphology of bumble bees make them ideal pollinators because of the speed at which they transfer pollen, the efficiency with which they gather pollen within various crops, and the increased endurance to fly in adverse weather for longer periods of time (Bigras-Huot et al. 1973, Stubbs and Drummond 2001, Stanghellini et al. 2002, Desjardins and Olivera 2006, Young et al. 2007). Other studies have also shown that bumble bee foraging activity starts earlier and ends later in the day than managed honey bees and they forage in lower temperatures. Honey bees begin to forage around 16ºC whereas bumble bees will start at 10ºC. Additionally their long tongues enable them to better pollinate flowers with deeper corollas than honeybees (Velthuis and van Doorn 2006).

In order for an investigation on the pollination efficacy of commercial, native bumble bees to occur, other details of the species biology had to be explored. As bumble bee nests differ fundamentally from those of the honey bee, an ideal housing strategy must be developed that will optimize colony growth and productivity. Currently, Koppert Biological Systems©, houses a colony in a plastic box within a larger cardboard box. Often, four colonies are placed together in a lighter yet larger plastic box (quad).

This project measured colony growth over the season in different crops, manipulated the recommended number of colonies per acre, examined placement effects (colonies were placed in the middle of the field (sun), edge of field (natural shade) and middle of the field with artificial shade (shade structure), and assessed overall bumble bee health and survival. We looked at horticultural effects on yield and quality of harvested crop. Studying these factors helped determine how to best use these native pollinators and increase crop yields for growers. Specifically, we developed best management practices for commercial bumble bee units in cucumbers, watermelon and strawberries in the state of Delaware. These crop specific, best management practices provide growers with guidelines on the most efficacious use of bumble bee units for their area. Ultimately, the goal was to produce recommendations to commercial growers in Delaware on how to best use B. impatiens for the pollination of these crops during the growing season.

References

Calderone, N.W. 2012. Insect pollinated crops, insect pollinators and US agriculture: trend analysis of aggregate data for the period 1992-2009. PLos One. 7:1-27.
Desjardins, E. C., and De Olivera. 2006. Commercial Bumble Bee Bombus Impatiens (Hymenoptera : Apidea) as a Pollinator in Lowbush Blueberry (Ericale : Ericaceae) Fields. Journal of Economic Entomology. 99: 443-449.
Free, J. B. 1993. Insect Pollination of Crops. 2nd ed. London: Academy, New York City, NY.
Goulson, D., W.O.H. Hughes, L.C. Derwent, J.C. Stout. 2002. Colony growth of the bumblebee, Bombus terrestris, in improved and conventional agricultural and suburban habitats. Oecologia. 130:267-273.
Goulson , D. 2010. Bumble bees: Behaviour, ecology and conservation, 2nd ed. Oxford Press. New York City, NY.
Koppert Biological Control Natural Pollination. 2011. http://www.koppert.com.
Robinson, G. E., R. E. Page, and R. E. Strambi. 1989. Hormonal and Genetic Control of Behavioral Integration in Honey Bee Colonies. Science 246: 109-112.
Stanghellini, M.S., J.T. Ambrose, and J.R. Schultheis. 2002. Diurnal Activity, Floral Visitation and Pollen Deposition by Honey Bees and Bumble Bees on Field-grown Cucumber and Watermelon. Journal of Apicultural Research 4I (2002): 27-34. Print.
Stubbs, C. S., and F. A. Drummond. 2001. Bombus impatiens (Hymenoptera: Apidae): an Alternative to Apis mellifera (Hymenoptera: Apidae) for Lowbush Blueberry Pollination. Journal of Economic Entomology 94: 609-616.
Velthuis, H. HW, and A. Van Doorn. 2006. A Century of Advances in Bumble Bee Domestication and the Economic and Environmental Aspects of Its Commercialization for Pollination. Apidologie. 37:421-451.
Young, HJ, DW Dunning, and KW Von Hasseln. 2007. Foraging Behavior Affects Pollen Removal and Deposition in Impatiens capensis (Balsaminaceae). American Journal of Botany 94: 1267-271.

Project Objectives:

In the growing season of 2012, 42 bumble bee quads were purchased from Koppert Biological Supply Company and were placed in four different crops; strawberry, watermelon, pickling cucumber, and pumpkin. Two quads were utilized for the strawberry crop. Obtained in March, the strawberry quads were placed in a sunny area along the edge of the strawberry field with shade structures and temperature recorders. These quads were visited weekly to conduct five minute foraging counts on each of the four colonies per quad.
During the first week of June, thirty quads were obtained for the watermelon crop. These quads were distributed evenly between three different fields of varying sizes. Upon placement, each quad was randomly assigned to a placement treatment that determined the nature of how it would be placed in the field. Quads were either placed in direct sun, natural shade or assigned a shade structure (Figure 15.). Three temperature recorders were available per field and randomly assigned to a single colony of a different placement treatment. In other words, one colony per one of the three placement treatments received a temperature recorder, per field. All colonies of each quad were tested weekly for five minute foraging counts and weight, to the nearest 0.5 gram. In the beginning of July the highest and lowest weighing colonies per field were sacrificed and dissected for comparisons between colony weight and colony cells and the number of bees found in the colony.

During the second week of July, ten additional quads were obtained to be placed in a single pickling cucumber field. Placement treatments in the pickling cucumbers were either sun or shade structure. Temperature recorders were also placed in colonies of different treatments. All colonies were examined weekly for five minute foraging counts and weight to the 0.5 gram. Additional foraging data within the pickling cucumber was gathered. These additional tests included counting the number of flower visits per minute/bumble bee, sweep netting pollinators along five, 50 meter transects for 30 minute intervals and counting honey bees, squash bees and bumble bees flying into and out of a 1m x 1m area at each 5 meter interval along the transect. Quads were removed just prior to pickling cucumber harvest and placed in a second pickling cucumber field. Quads in the second field were overrun by honey bees and were then placed in a pumpkin field until the end of the season.

Each hive was dissected at the end of the season or whenever it is found dead. Dissection methods include obtaining weight of the wax, counting the number of queens, workers and males in the nest and recording other found nest commensal organisms. Wax and bees within the colonies were sent off to the USDA for pesticide analysis
Crop product information was obtained for watermelon and pickling cucumber.

In watermelon, fruit set and fruit yield data were obtained. When examining the field for fruit set, 5 plants at varying distances from each quad (10, 20, 30, 40 and 50 meters) were located and the number of fruit (at least as large as a softball) were counted. Fruit set test was conducted twice in each field during the season. The first was conducted when fruit in the field were the average size of a softball and again just prior to the first harvest. Finally, fruit yield data were obtained in one of the three watermelon fields, just prior to each harvest. A 10 meter transect adjacent to each quad was flagged and all harvestable fruit within the transect was harvested and weighed.

Crop yield data was gathered by harvesting eight, 10 yard plots on various areas of the first pickling cucumber field. GPS data points of each plot were taken to mark distance from bee quad. The weight of pickles harvested in each transect was recorded. This experiment was not run in the second pickling cucumber field because of the hasty removal of the bumble bees to avoid being overrun by honey bees.

A pollen transfer experiment was attempted in both pickling cucumber fields. This experiment focused on the bumble bees’ ability to transfer pollen from flower to flower. Flowers were bagged with paint strainers the day before anthesis. The next day, experimenters attempted to control bumble bee visits to the isolated flowers. This experiment was not successful, as so few bumble bees were present in the field to pollinate these flowers.

Most goals that measured aspects of bumble bee biology were reached. Encountered problems were centered on our attempt to determine a measurable effect on the pollinated pickling cucumbers.

Cooperators

Click linked name(s) to expand
  • Gordon Johnson
  • Lydia Trumbull

Research

Materials and methods:

The field investigation started during the spring and summer of 2011 and 2012 on six farms throughout the Kent and Sussex Counties of Delaware. There will be two main areas of investigation, each with various subsets:

The Biology of the Bumble Bee

The bumble bee study included various assays that aimed at determining the most ideal conditions for a bumble bee nest. Commercial bumble bee colonies and shaded structures, currently being tested within the company, were obtained from Koppert Biological Systems©. Quads were situated in a variety of locations and conditions within each field. Location treatments were edge (natural shade) and in field placements (sun or shade structure). Colony condition treatments were full sun exposure without shade structure, full sun exposure with shade structure, wooded shade without shade structure. The quads were randomly assigned one the above treatments. Following the Goulson et al. (2002) study, each quad is weighed to the half gram before being opened and on a weekly basis thereafter to determine productivity of the hive. Three empty boxes provided by Koppert Biological Systems© were weighed and averaged allowing to more accurately determine biomass.
Colonies throughout the study were be outfitted with data recorder Hobos that were used to measure temperature and relative humidity at half hour intervals throughout the study.
Each hive was dissected at the end of the season or whenever it is found dead. The wax nest was carefully stripped from the cotton structure provided from Koppert Biological Systems© and was weighed. Perished specimens that remained in the hive in addition to wax samples were collected and sent for pesticide analysis. This testing determined levels of chemical accumulation found in the bees and the wax in the hive. Growers shared season long pesticide records and they were compared to other results gathered from the analyses. Pollen within the hive was collected to determine foraging range and preferences previously conducted by Munidasa and Toquenaga 2010.Throughout the project, each pollination unit was given a location treatment, as described above. Each treatment looked at how the unit behaves given its particular location treatment. Weight and foraging tests were the two methods used to determine the productivity of a unit, and productivity measurements were translated to pollination ability on a crop during the growing season. Ultimately, the data collected from these experiments helped to determine how to best place bumble bee units within a field.

The Crop Product

Strawberry

Strawberry (experiment ran weekly from the end of March 2012-July 2012)
Two quads were placed along the edge of the strawberry field. Pollen was collected from workers of colonies in both treatments and pollen content was compared. Further, worker foraging was observed to measure productivity. Each hive was examined for 5 minutes each week and the activity of bees entering and leaving the hive was recorded. Hobo data recorders were used to determine hive thermoregulation by measuring temperature and relative humidity. The early nature of the strawberry season allowed for the greatest observation of these pollinators throughout the season and pollen basket dissection determined which plants the bees are visiting.

Watermelon

Watermelon (experiments were run weekly from June 2012-October 2012)
Hive weight, measured to the half gram, was collected on a weekly basis throughout the season. Further, foraging data was also taken by counting bees flying in and out of the hive for 5 minutes. Watermelon surveys were conducted twice on each field throughout the season. These surveys counted the number of fruit per plant when watermelons were softball sized and then once again right before harvest. Relative humidity and temperature were also measured in hobo data loggers placed in colonies throughout the field. The goal of the watermelon study was to determine how the location treatment of the quad affects longevity and production of the bumble bees, and how the presence of bumble bees in a field affects the fruit set of the watermelon they pollinate.

Pickling Cucumber

Pickling Cucumber (experiments were run weekly from July 2012-August 2012
Experiments in the pickling cucumber crop mirrored those in watermelon, but also added additional foraging tests. Foraging activity data was gathered by counting the number of flower visits per minute/bumble bee. Pollinators were then collected along five, 50 meter transects for 30 minute intervals to determine what species were actively on the plants. Further, at each 5 meter interval along those transects, bees were counted as they flew into the area over a one minute period. Finally, bees were moved to a second field after the first harvest to determine the hardiness of bees after being transferred. Crop yield data was going to be gathered by harvesting eight, 10 yard plots on various areas of the field. GPS data points of each were taken to mark distance from bee quad. Finally, experiments that focused on the bumble bees’ ability to transfer pollen from flower to flower were attempted For these experiments pollinators were meant to be caged and isolated with cucumber blooms and pollen and female receptacles would be weighed to record pollen deposition. Pollen transfer frequency data was also meant to be compiled. (The experiments designed to test the growth and development of cucumbers were unsuccessful, see question 3).

Research results and discussion:

In comparing treatments by total foraging of a colony through the season all colonies placed with shaded treatment yielded higher total foraging counts than those placed in the sun (Figures 2,3), ( F2, 99=8.31, P=0.0005). Each colony’s peak forage counts and the date of the peak was extrapolated and compared by treatment and field. No difference between treatments was detected (Figure 4), (F2, 98=1.22, P=0.2986). The day in which an individual colony performed their peak forage was calculated to indicate the length of time the colony was still actively building up before decline in activity began. When compared by treatment, days to peak forage was not significant (Figure 5), (F2, 98=1.39, P=0.2532). Two foraging counts were conducted on the same day each week that aimed to reflect morning and afternoon foraging. We found that colonies generally foraged significantly more in the morning hours (before 11am) than they did in the afternoon (after 11am). Total season counts of morning foraging were measured against total season afternoon foraging counts, by treatment. Difference was seen by treatment, by time of day and by their interaction, treatment x time of day foraging activity of the colony was higher in the morning hours than in the afternoon, but the quad treatment affected the level of the differences seen (Figure 6), (treatment: F5, 198=4.43, P=0.0131, time: F5, 198=8.54, P=0.0039, treatment x time: F5, 198=4.29, P=0.0149).

Natural shade and shade structure treatments had higher average weights than those in the sun (Figure 7). Change in weight from the beginning of the season to the peak weight showed how much a colony gained at the height of the season. The natural shade had the highest weight change, followed by shade structure treatments, then the sun (Figure 8), (F2, 99=21.07, P<0.0001). The number of days it took for the colony to reach its peak weight was tested against its treatment and field. All shaded treatments took a longer time to reach their peak weight than those colonies in the sun (Figure 9), (F2, 93=16.59, P<0.0001).

At the end of the season when each colony was determined to be ‘dead’, the colony was collected and analyzed. The number of total cells counted in each colony was compared against the treatment that it was given and the field in which it was placed (Figure 10). Both shaded treatments had more total cells than sun treatments (F2, 91=12.08, P<0.0001). The number of bees that remained in the colony were counted with each post mortem analysis and compared to the colony’s site and treatment. More dead, adult bees were left in the colonies with sun treatments than the colonies with two shade treatments (Figure 11), (2011: F4, 31=5.85, P=0.0013, 2012: F2, 97=5.95, P=0.0037).

Average weekly temperature (Figure 12) and relative humidity (Figure 13) of the colonies did not differ in colonies with different treatments, (temperature: F2, 61=0.34, P=0.715, relative humidity: F2, 20=3.30, P=0.0579).

Watermelon surveys were conducted that determined fruit set by distance to bumble bee quad. One plant was chosen at 5 different distances per quad. The total number of fruit counted during both surveys was compared by distance the chosen plant was from quad (number of fruit on a plant 10 meters from quad, 20 meters, 30, 40, 50 (Figure 14) (F16, 268=0.33, P=0.8575).

The variety of placement treatments including the various designs of the shade structures provided by Koppert Biological Systems© caused differences in the performance of various metrics assessed during the field season. These metrics tested colony productivity by assessing forage rates, colony weight and cell production within the colony. All treatment placements generally provided a condition for the colony that was superior to a sun placement in relation to productivity tests results. These results align with the need for bumble bees to maintain their nest temperature at 30?C. This temperature is maintained by bumble bees producing heat at low ambient temperatures or fanning the nest when the weather gets too warm (Goulson 2010, Heinrich 2004, Vogt 1986). These temperature-regulating actions require energy, thus, energy spent regulating temperature is not available to optimize colony productivity (Heinrich 2004). The less energy available decreases the allotment of energy for nectar and pollen foraging and overall reduces intrinsic worth to growers. Indeed, in most five minute foraging counts, weight analyses, and nest post mortem analyses, the shaded colonies foraged more, weighed more, or performed in a way that indicated higher productivity, than colonies placed in the sun. Further, the more worker bees needed to thermoregulate a colony, equates to less bees available for brood maintenance or other duties needed for the colony (Vogt 1986).

Interestingly, we found that when counting dead, adult bees in the post mortem analyses, sun treated colonies left more bees than their shaded counterparts. Perhaps this is evidence that energy expended for colony hygienic behavior decreases when more energy is needed to maintain colony temperatures. In a healthy colony, dead, adult bees are most likely removed to reduce inevitable occurrences of disease when chronically exposed to the dead (Cremer et al. 2007). Evidence of dead immature bee removal was witnessed throughout the experiments, especially after delivery of the commercial quads to the field. Larvae that did not survive the trip were removed by worker bees and dropped outside of the colony. The removal of deceased adult bees is speculated but was not specifically witnessed during this project.

Through these experiments we can conclude that commercial bumble bee units must be placed under some shade to increase longevity and overall productivity throughout the growing season. This statement is displayed in the watermelon temperature figure, Figure 12. This figure demonstrates the ability for bumble bees to thermoregulate their nests, despite the differences in sun exposure. However, as the season progresses the bumble bees in the sun stop regulating the temperature of their colony earlier in the season than the other two treatments. The temperature regulation stops presumably because the colony is no longer active and thus is no longer foraging. The temperature of the sun treated colonies increases while the other two treatments continue on, regulating the temperature of the colony.
Overall, the experiments testing colony productivity and colony placement presents much evidence that shaded colonies expend less energy and expend less general worker resources thermoregulating the colony, during the summer growing months. This relaxation from maintaining colony temperature allows for the energy to be directed towards productivity as witnessed by the increase in foraging and weight in colonies placed in shade.

Pesticides were detected in the bees and the wax of each sample tested (see Table 1). LD50 were taken from Pesticide Properties Database (PPDB), a tool developed by the University of Hertfordshire in the UK, unless otherwise indicated. The LD50s are for honey bee contact or oral exposure for 48 hours as bumble bee exposure has not been investigated to the same extent in which it has been explored in honey bees. We find these LD50s inapplicable to our study for a few reasons. First, as bumble bees are larger than honey bees, they are known to consume more pollen and nectar on a daily basis than honey bees. If pollen and nectar contain pesticide residue, bumble bees will likely come into contact with these chemicals at a faster rate, by the simple fact that adult bumble bees eat larger quantities per day than honey bees. Second, in our study within the watermelon field, bumble bees foraged on more flowers per minute than honey bees. Therefore, bumble bees can be exposed to larger quantities of pesticides due to their increased visitation rates. Further, as stated above, the LD50s are applicable for an exposure of just 48 hours (PPDB). In our experiment, the fields in which our bumble bees foraged were generally sprayed weekly; and the chemicals found in the substrate tested were from a season’s worth of these weekly sprays. Thus, the commercial bumble bees are generally exposed to pesticides over a much longer time than is indicated in the given LD50s. Also there is growing evidence that exposure to multiple pesticides at a time creates synergisms leading to possible additive effects to honey bees. Much of the possibility for synergism has been shown between fungicides and neonicotinoids and pyrethroids (Johnson et al. 2010), all of which were found in the pesticide analysis. Bees are often exposed to more than one pesticide at a time within the field and are therefore subject to this multiple pesticide synergism. Much of these tests have been conducted in the lab rather than in practical applications in the field and thus field studies testing synergism are warranted for the future (Iwasa et al. 2003, Johnson et al. 2009, 2010, Pilling and Jepson 1993). Currently, the US EPA is working on developing studies to test chronic honey bee exposure. At this time, there are no formal guidelines developed to conduct chronic toxicity tests on honey bees, and to the best of our knowledge, there is no information available looking at bumble bee chronic exposure to these chemicals. Therefore, due to lack of scholarly literature and lack of funds that would allow for our own colony level pesticide analyses (rather than field) we have no real idea of the effects of the chemicals on the pollination ability of the commercial bumble bees within the field. Further, we call for such future analyses to be considered and conducted, as we believe not enough is known about chronic exposure of pesticide sprays to pollinators both commercially managed and native. In the meantime, as some pesticides detected in this study are those sprayed during many mosquito control programs we call for the creation of bumble bee registry programs. The bumble bee registry can be run in conjuncture with existing state honey bee registries for the notification of mosquito abatement sprays to protect the purchased commercial bumble bee pollinators.

Research conclusions:

Another aim of this project is to disseminate project information to the public. In 2012, the project was presented four times to public audiences. In January a presentation was given to roughly 150 growers during the Vegetable Crop Section of the Delaware Agriculture Week Meeting in Harrington, Delaware. A presentation was given in April to the New Castle County, DE Beekeeping Association monthly meeting. The 40 attending members were honey beekeepers of the county in which the University of Delaware resides. In June, a presentation was given to 15 researchers at the Bumble Bee Conference at Utah State University in Logan, UT. After this presentation, a meeting was held with members of the USDA-ARS lab situated on Utah State’s campus and new ideas were solicited and discussed. Finally, in November of 2012 a presentation was conducted at the Entomological Society of America Annual Meeting held in Knoxville, TN. Three thousand professional entomologists from all over the country were in attendance at this meeting. The presentation was given to 50 people in a session for pollinators and all meeting attendees had access to the presentation.

Overall, results of the project were disseminated to Delaware growers. Growers’ reactions to the study were not solicited; however, the results of this project will likely increase the use of commercial bumble bees in watermelon and strawberry plantings throughout Delaware. This is especially likely if honey bee prices continue to rise while their availability continues to falls. The Best Management Practices were published in the UD Weekly Crop Update that is disseminated to roughly 200+ growers, this spring.

The BMPs shared are as follows:

1. Bumble bees can be used for strawberry and watermelon but not for pickling cucumber horticultural crops.
2. Place bumble bees in the field after crops have begun to bloom.
3. Allow time for bees to settle before opening units.
4. Close bumble bee units before each pesticide application.
5. Dispose of bumble bee colonies in a timely and humane fashion.
6. Bumble bees can be placed in the middle or on the edge of the field.
7. Place bumble bees under shade, to increase productivity and longevity of the bumble bees.
8. Keep bumble bees away from honey bees.
9. Strap down bumble bee units.
10. Bumble bee units may successfully be transferred to another field.

Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary:

Education/outreach description:

The following is a list of avenues in which information from this project has been publically available or presented. The list of outreach activities have been categorized into two groups of either highly effective outreach or moderately effective outreach. Given our main goal was to reach out to growers we determined that those methods that focused exclusively on growers were most effective in publicizing our work. Further, the response from these outreach attempts were positive in that our efforts were informative and constructive and growers gained welcomed knowledge. In the moderately effective outreach category are the outreach efforts that were given to an audience that did not include growers (mostly bee keepers and academics). Despite missing the main target audience of the project, these efforts were important as they shared research ideas with other professionals in the field. Oftentimes feedback was received allowing for the expansion and fine tuning of our research methods and overall goals. Finally, this list does not include publications that are in the final stages of the writing process and we are optimistic that these articles will reach publication in 2014. These publications will be submitted to HortScience, The Journal of Economic Entomology, and Bee Culture Magazine.

Highly effective outreach
• 2011 Mid-Atlantic Vegetable Workers Conference (November 2011) (audience of 40)
• 2012 Delaware Agricultural Week (January 2012) (audience of 110)
• 2013 Vegetable Growers Association of NJ Convention (February 2013) (audience of 60)
• 2013 Mardel Watermelon Growers annual conference, Cambridge, MD (March 2013) (audience of 80)
• University of Delaware Cooperative Extension – Weekly Crop Update (April 2013) (audience of 200)
Moderately effective outreach
• New Castle County Beekeepers Monthly Meeting (April 2012) (audience of 70)
• USDA-ARS Pollinating Insects Lab (June 2012) (audience of 15)
• Eastern Apicultural Society Native Pollinator Workshop (August 2012) (audience of 100)
• Entomological Society of America (ESA) Meeting (November 2012) (audience of 100)
• ESA Eastern Branch Meeting (March 2013) (audience of 35)

Project Outcomes

Project outcomes:

While there could be clear financial implications of our study to Delaware growers, this analysis was outside of the scope of this project and was not determined.

Farmer Adoption

As above, this information was not solicited and is currently, unknown.

Assessment of Project Approach and Areas of Further Study:

Areas needing additional study

Future projects need to be conducted to address the process of pollen transfer down to the number of displaced pollen grains per bee visit. Such an experiment will clarify the effectiveness of each bee visit. Further studies are needed to determine what number of hives/colonies per acre is truly most efficient. Our study ran into difficulties answering this question as it was difficult assessing the level of pollination occurring from other native pollinators and non-native honey bees.

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.