The purpose of this project is to maximize the health and size of on-site populations of native pollinators for crops that require sonication pollination, such as blueberries, cranberries, tomatoes, eggplants, peppers,and melons. Considering recent declines in pollinator populations and the expense and risk of spreading parasites associated with managed bee populations, tailoring effective on-site pollinator habitats has become important for farmers who grow pollinator-dependent crops. Most literature that provides recommendations for designing on-site pollinator forage and habitats for farmers assume all pollinators share similar foraging needs. While some literature distinguishes itself by supplying profiles of the behaviors and nesting habitats of various pollinators, the authors tend to recommend the same species of flowering plants as forage for all insect pollinators. However, recent research has shown that, if provided enough options, some pollinators strategically will select those plants that provision for particular ratios of protein, lipids, and nutrients. Compared to honey bees (Apis mellifera) foraging in the same landscape, bumble bees (Bombus impatiens) – one of the primary pollinators of sonication pollinated crops – show a tendency to preferentially forage on plant species with pollen that contains higher protein and particular macronutrient ratios. In addition, to avoid or dilute the negative effects of toxic phytochemicals, bumble bees may collect pollen from multiple host-plant species. This research will attempt to develop a selection of plant species and strategies from which farmers growing crops requiring sonication pollination can choose for establishing on-site pollinator habitats that incorporate these new and consequential findings.
1.Consult with farmers of crops requiring sonication pollination to explore:
a.The methods by which they meet their crops’ pollination needs
b.The amount they spend on meeting these pollinator needs
c.The proportion of farmers who depend on on-site pollinator forage and habitat
d.The average amount of marginal land farmers can devote to on-site pollinator forage
e.Those plant species these farmers have found that effectively increase native pollinator populations and increase crop yields
2.Establish relationships with farmers of crops requiring sonication pollination and receive their permission to collect data on native pollinator visitation to their crops. This data will be used to:
a.Compile a list of those species of native pollinators that most frequently visit crops requiring sonication pollination
b.Compile a list of perennial and biennial plant species preferred by these crop pollinators for forage when the farmers’ crops are not in bloom.
3.Create a list of native and near-native perennial and biennial plants preferred by pollinators of crops requiring sonication pollination using these methods:
a.Interviews with farmers
b.Interviews with native pollinator conservation experts
c.Literature review of scientific and green industry publications
d.Passive crowdsourcing of on-line photographs of floral visitation by arthropods that provide sonication pollination
4.Establish common garden plots of the expanded list of herbaceous forbs and flowering woody shrubs that will supplement existing plots of native New England plant species at the University of Connecticut Research Farm in Storrs, Connecticut.
5.Collect data concerning visitation by targeted pollinators to common garden plots. Such data collection will include:
a.Vacuuming of pollinators that visit plotted plants while in bloom and presenting pollen
b.Observing pollinator visitations over set periods of time
c.Photographing the plots of plants at peak bloom to count the number of flowers per unit of area in order to calculate frequency of visitation per unit of area covered by forage plants.
6.Conduct statistical analysis of pollinator visitation to determine those forage species most preferred by targeted group of native pollinators.
7.Write report that compiles collected data and information.
- Survey farmers of crops requiring sonication pollination.
Project participants, under the supervision of Dr. Robert Ricard, will develop a set of surveys and interview instruments that will explore how farmers who grow crops that benefit from sonication pollination meet their crops pollination needs. We will develop a structured survey instrument which consist of 25-35 items, including open-ended, opinion-based, and closed-ended questions structured on a five-or seven point scale. The surveys will include questions related to the following topics:
- The methods by which they meet their crops’ pollination needs.
- The amount they spend on meeting these pollinator needs
- The proportion of farmers who depend on on-site pollinator forage and habitat
- The average amount of marginal land farmers can devote to on-site pollinator forage
- Those plant species these farmers have found that effectively increase native pollinator populations and increase crop yields
Questions will also explore the variety of species of crops grown, amount of land devoted to crops, and annual yields. A select number of surveys will be solicited to participate in more in-depth in-person interviews. These surveys will also be used to find possible collaborators that will allow for the establishment of on-site pollinator habitats. Surveys will be designed to collect quantitative and qualitative data suitable for statistical analysis.
Farmers will be found using information from state agricultural departments, state extension offices, the New England Farmers Union, the New England Small Farm Institute, and state Northeast Organic Farming Association.
- Establish relationships with farmers of crops requiring sonication pollination and receive their permission to collect data on native pollinator visitation to their crops.
- Record periods of anthesis (bloom time) for each species of crops.
During the first growing season of the study, the anthesis (bloom time) for each crop species at each participating farm will be recorded. This data will help with the determination of which plant species to include in the neighboring pollinator habitats. It is especially important that, when crops are in bloom and requiring pollination, that the blooms within the habitat do not compete with the crops for pollinator services. Only those species that do not share simultaneous bloom periods will be included in habitat plantings.
- Collect data concerning pollinator visitation to the farms’ crops.
During the first growing season of the study, white, yellow, and blue plastic trap pans will be placed within the plots of crops during before, during, and following anthesis. Each pan will be filled with water and dishwashing liquid, which will prevent insects from leaving the water because they cannot break the surface tension. Research has shown this technique to be one of the most effective for collecting crop visitation (Campbell & Hanula, 2007; Roulston et al., 2007; Vrdoljak & Samways, 2011). Our own research on willow (Salix) pollinator visitation has proven the effectiveness of this approach.
Although we will not be establishing pollinator habitats on cranberry farms for lack of resources, we will collect pollinator visitation data to determine whether cranberries share pollinators with highbush blueberries (Vaccinium corymbosum). In addition, although we will collect pollinator visitation to Solanaceae and Cucurbitaceae crops, we will conduct crop yield trials only on tomato plants.
Bowls will be placed in the fields of each participating farm on at least two different days during anthesis. Each time, two-thirds of the bowls will be placed at 0830 hours EST on calm days. Half of these two-thirds bowls will be collected at 1200 hours EST to determine which pollinators visit early in the day. This data will be especially important for those crops in the Cucurbitaceae family, which open and close before noon. Another third round of bowls will be placed out at 1200 hours EST to determine if some pollinators are later day visitors. All remaining bowls will be collected at 1530 hours EST.
Bowls will also be put out among fields of crops approximately two weeks preceding and two week following crop anthesis to confirm their presence and abundance correlates to the attraction to the crops’ presentation of rewards.
Samples of pollinators collected using the colored bowl method will be stored in 70% ethyl alcohol and subsequently sorted and identified to the lowest taxonomic level using various identification resources, including the insect collections at the University of Connecticut, Yale Peabody Museum of Natural History, and Harvard University Museum of Comparative Zoology, as well as the online key to eastern North American bee species at www.discoverlife.org. Dr. Sam Droege of the United States Geological Survey Patuxent Wildlife Research Center will assist in the confirmation of the final identifications of pollinator species.
We will also conduct on randomly selected highbush blueberries the three techniques for determining pollinator visitation described in Section 5: Collect data concerning visitation by targeted pollinators to common garden plots (see below) to help determine the proportion of pollination each species provides to the crop. These findings will help to determine the proportion of native plants that would need to be planted in each habitat.
- Measure crop yields both before and after the establishment of on-site pollinator habitats using exclusion bags.
During the first year of research, we will determine optimal placement of the on-site pollinator habitat for each participating farm relative to each crop. Fields of crops bordering the habitat will then be divided into two portions: the outer half that borders the pollinator habitat and the inner half that is furthest from the habitat plantings.
Ten healthy, mature highbush blueberry plants will be randomly selected within both the outer and inner halves. During each year of the study, the fruit of each selected plant will be weighed and compared to the prior year.
During the second and third year of the project, a different set of fifteen highbush blueberry plants will be randomly selected within both the outer and inner halves. Prior to bloom, one flower cluster on each bush will be designated randomly to be open pollinated while a similar cluster on a separate shoot will be excluded from animal pollination by enclosing it in a fine mesh bag attached to the stem with a twist tie. The total number of flower buds in each cluster will equal the same number on each bush. Following bloom time, organza mesh bags will be placed over the open pollinated cluster to control for any potential effects of bags on berry maturation.
Prior to harvest, when approximately 50% of the fruit per cluster are ripe, the open and bagged berry clusters will be collected and the number of fruit will be recorded to determine fruit set. Research has shown that seed number and berry weight directly relate pollination success in in highbush blueberry crops (Brewer & Dobson, 1969). Average berry weight will be determined for each cluster. The five largest berries from each cluster will squashed in a plastic bag and the number of mature seeds will be recorded.
To estimate the percentage increase in fruit production, the differences between the average percentage fruit set and fruit weight of the open and bagged clusters will be calculated. These numbers will be used to extrapolate the percentage increase in fruit abundance per hectare based on bush spacing and flowers per bush. To calculate whether the overall costs and benefits of the establishment of the pollinator habitats are returned over the coming years, Dr. Aaron Hoshide will modify his existing Excel spreadsheet program, which will consider such expenses as labor, land preparation, plant materials, and site maintenance.
To study the impact of pollinator habitats on tomato yield, we will determine during the first year where the pollinator habitat will be located relative to field of tomatoes. Once again, the field will be divided into halves: the half closest to where the habitat plantings will be established and the half furthest from the habitat. Each year, including the first year without the habitat, ten plants will be selected randomly in both halves of the fields. Once again, two clusters of flowers on the same plant will be chosen that have the same number of flowers. Before the flowers open, organza mesh bags will be placed over one cluster while the other will remain without a bag until first signs of fruit development. Once the open pollinated cluster displays fruit development, it too shall be enclosed with an organza bag (Santos et al., 2014).
Once fruits begin exhibiting a red color, fruits will be harvested. We will estimate the quality of each fruit according to the following parameters (1) ratio between the diameter and height (roundness) (Del Sarto et al., 2005) measured using a digital pachymeter; (2) fresh mass using a digital weighing scale; (3) number of seeds counted directly; and (4) total sugar content by using a portable refractometer after seed removal and the processing of the remaining portions in a food processor,
- Create a list of native and near-native perennial and biennial plants preferred by pollinators of crops requiring sonication pollination with a particular focus on early spring blooming species by using these methods:
- Interviews with experts in the fields of native plants, pollinators, and ecological conservation
- Literature review of scientific and green industry publications
- Passive crowdsourcing of on-line photographs of floral visitation by arthropods that provide sonication pollination
Considering the importance of providing sufficient nutritional sustenance to pollinators, especially bumblebees (Bombus spp.), early in the spring to support their growing colonies, we will use a varieties of methods to expand the choices of native plants usually recommended in the list of plants recommended in native plant lists. We will survey the group of experts in the field of New England native plants we have cultivated in the course of our research. In the course of our search of scientific and industry publications, we will pay particular attention to research that focuses on plant pollen provisioning since the protein in pollen appears to be a limiting factor in bumblebee health. In addition, we will use an innovative method recently outlined in a scientific journal called passive crowdsourcing that uses images of arthropod floral visitation stored on-line to determine the correlation of pollination visitation. This method was developed as “a useful screening tool to identify candidate plants for pollinator habitat restoration efforts directed at wild bee conservation” (Christie & Douglas 2016).
Native plants selected for study in a common garden established at the University of Connecticut Research Farm will be evaluated for their relative attractiveness to insects that provide sonication pollination. These plants will meet the following criteria: (1) native perennial plants, (2) adapted to agricultural field and woodland border conditions, (3) species representing diverse bloom periods that span from early spring to late autumn, (4) species representing a variety of plant families, with varied morphologies and flower colors, (5) both herbaceous forbs and woody shrubs, and (6) preferably ecotypes that originate from the New England region.
In an attempt to use mostly New England ecotypes of each species, we will either buy plant materials from local nurseries that specialize in local native ecotypes. When species are not available through nurseries, we will use the consulting services of the New England Wildflower Society (NEWFS), with whom we have a longstanding relationship from previous research collaborations. NEWFS has mapped the New England region for remnant plots of regional ecotypical native plants from which seeds can be collected.
- Establish common garden plots of native New England herbaceous forbs and flowering woody shrubs species at the University of Connecticut Research Farm in Storrs, Connecticut.
A study site will be established the University of Connecticut Research Farm in Storrs, Connecticut. It will consist of 1 meter2 blocks spaced 4 meters apart in a randomized block design consisting of five replicates of each plant species. Woody shrubs will be mixed with herbaceous plants. One woody plant will occupy each square meter plot, while four to nine herbaceous plants will occupy each square meter plot, depending on the growth habit of each species. To reduce weed pressure, weed fabric that allows penetration of water and air will be used for plot of herbaceous species.
For this proposed study, we can use and build upon approximately 160 plots of perennial and biennial herbaceous plants native to the New England region we established at the University of Connecticut Research Farm in Storrs, Connecticut as part of previous research for the New England Transportation Consortium. Each plot measures 2 meters x 2 meters and consists of 16 to 25 individual plants of one species. There are at least 46 forbs species, 40 grass species, and 20 monocot grass-like species, including 16 sedge (Carex) species. Several of the species have multiple plots, each consisting of ecotypes from different regions from around New England, which we used to observe differences in phenologies and morphologies. We have also established 30 plots of 15 willow (Salix) species native to New England. Each plot is 2 meters x 2 meters and consists of five plants. Two plots were established for each species, one consisting of female plants, the other male. The willows consist of species that bloom in early, middle, and late-middle portions of spring.
- Collect data concerning visitation by targeted pollinators to common garden plots.
- Vacuuming of pollinators that visit the flowers of plotted plants while in bloom and presenting pollen
Flower visitors will be sampled weekly from the opening of the first blooms (usually starting in late February or early March in Connecticut for early blooming Salix) until mid-to-late October on calm days between 0830 and 1630 hours EST. Plants will be sampled during peak anthesis (full bloom period), and those samples collected before, during, and after the week of peak anthesis based on the weekly counts of the number of open flowers on each plant species. We will use BioQuip’s Heavy Duty Hand-Held cordless rechargeable vacuum aspirator. Each sample will be frozen, and pollinators subsequently will be sorted and identified to the lowest taxonomic level using various identification resources including the insect collections at the University of Connecticut, Yale Peabody Museum of Natural History, and Harvard University Museum of Comparative Zoology, as well as the online key to eastern North American bee species at www.discoverlife.org. Dr. Sam Droege of the United States Geological Survey Patuxent Wildlife Research Center will assist in the confirmation of the final identifications of pollinator species. The number of bees per sample will be recorded and averaged over the number of collections made during peak bloom per plot for analyses.
- Observing pollinator visitations over set periods of time
Timed observations of bees visiting each plot in Flower visitors will be sampled weekly from the opening of the first blooms until mid-to-late October on calm days at set times chosen between 0830 and 1630 hours EST. Each plot will be observed once during peak bloom for 5 minutes, for a total of five replicate observations per plant species. Bees visiting the plants during this time will be recorded with Canon EOS RebelT5i fitted with a Canon EF-S 24 mm f/2.8 STM Macro lens.
Using a technique modified after research by Frankie et al. (2005), plant species visited by five or more bees on average during either vacuuming or visual observations will be considered highly attractive species. Those visited one to five times will be considered moderately attractive, and those visited less than one time were considered least attractive.
- Photographing the plots of plants at peak bloom to count the number of flowers per unit of area in order to calculate frequency of visitation per unit of area covered by forage plants.
For each plant species evaluated, we will record their floral area per meter square, corolla width, and corolla depth during peak bloom. Using digital images taken at the site by a Canon EOS RebelT5i fitted with a Canon EF-S 24 mm f/2.8 STM Macro lens, with a ruler in each image for reference, we will estimate floral area per meter square of each plot by counting the number of open flowers weekly per plot and multiplying them by the average area of 10 representative flowers or clusters. Digital images will be prepared for analysis by using Adobe Photoshop CC software to convert flower images into white space. Scion Image freeware (Version 4.0.2, https://en.wikiversity.org/wiki/Scion_Image. software.informer.com/) will be used to calculate individual floral area based on the images.
- Conduct statistical analysis of pollinator visitation to determine those forage species most preferred by targeted group of native pollinators.
We will use analysis of variance (ANOVA) with Tukey-Kramer adjusted means separation (PROC MIXED, SAS v 9.1) to determine differences among plant species in the number of pollinators that visit plants in early spring (March to April), late Spring (May to early June), summer (June to August), and fall (September to October) for vacuumed samples and timed observations. Simple linear regression analyses will be conducted with each pair of floral characters to check for autocorrelation, and a multiple linear regression analysis will be conducted on the pollinators obtained during vacuum sampling to determine whether bee abundance (honeybees, bumble bees, wild bees other than bumble bees, and all wild bees) and richness (number of different bee taxa represented in the samples collected from each plant species) varies with average floral area during full bloom.
- Identify those species of pollinators that visit both crops that benefit from sonication pollination and flowering plants native to New England. Determine which pollinator species are known to provide sonication pollination.
After collecting data concerning pollinator visitation to the crops and to the common garden of native plants, we will determine which pollinator species they share. We will also determine the proportion of each species that visits each crop and will use this information to proportion those native flowers to which each native pollinator prefers.
- Establish on-site pollinator habitats on six farms that grow crops that benefit from sonication pollination, using the data collected from common garden plots.
Habitats on each farm shall include pollinator food resources in the form of blocks of herbaceous native forbs and hedgerows of woody shrubs. Herbaceous forbs will include species suited for full-sun open fields and part-sun woodland borders. These blocks will be planted using plugs grown in the research greenhouses of the University of Connecticut, Storrs using preferably New England ecotypical seed. To reduce weed pressure, weed fabric that is both water and air permeable. Holes shall be melted into the fabric using the circular end of a propane weed burner. Spacing of the holes and plants shall be determined by the growth habit of each species. The ground beneath the hedgerows shall be mulched using pine bark.
The number of each native plant species to be included in each habitat shall be determined by the pollen and nectar needs of the pollinators and the size of the pollinator populations required to pollinate the number of crop plants on each farm. Using the research by Dicks et al. (2015), flowers will be allocated to service those proportion of pollinators that have been determined will be present at any point in the growing season. For example, if particular Bombus species are the only pollinators present in early March, plants species that flower at that time and are preferred by these species shall be included in the planting. Since predominately queens will be present early in the season, the number of plants required would be less than that which would be required from June to August, when colony sizes peak.
In addition, while each bloom period will include flowers with differing structures by which pollinators with various tongue lengths can access pollen and nectar, the proportion of these flowers available will be calculated to conform to the proportion of pollinators present in that portion of the growing season. Attempts will be made to include at least two species of suitable morphology most preferred by each pollinator for each portion of the growing season.
In an attempt to determine the proportion of pollinator habitat that would return the cost of its investment in the form of crop increase, the size of each habitat shall vary among participating farms. We will use Dicks et al.’s (2015) proportions of a minimum of 1-3% of herbaceous floral resources and 500-2000 meters of hedgerow per 100 hectares available at any one time as our guiding baseline. Therefore, two farms shall have herbaceous floral resources toward the beginning and end of the season when nutritional demands are lowest that equal 1% of the demand required to effectively pollinate either highbush blueberry or tomato crops and floral resources that equal 3% of crop pollinator demands during peak summer pollinator nutritional demands. For these two farms, hedgerow proportions shall range from 500 meters/100 hectares during low demand periods and 2000 meters/100 hectares during peak demand. These percentages and proportions shall be lowered to .5-1.5% and 250-1000 meters/100 hectares for two farms and 1.5-4.5% and 750-3000 meters/100 hectares for the remaining two farms.
Research has pointed to three main factors that directly regulate bee populations: food resources, nesting resources, and “the availability of refugia from incidental risks, including pesticide exposure” (Dicks et al., 2015; Roulston & Goodell, 2011). However, Roulston and Goodell found that for wild bees the greatest limiting factor was loss of floral resources. Therefore, while the main focus of this research will address floral resources, we will include provisions to address the other two factors.
In terms of nesting resources, habitats will include plantings of bunch grass and/or Carex species for those pollinator species research shows prefer to nest within or beneath these bunches. Farmers will also be provided with wood structures for species, such as carpenter bees, that prefer to tunnel and nest in wood.
In terms of pesticide exposure, farmers will be required to provide any treatments used on their properties that could be considered pesticides, whether non-organic or organic. Farms with limited pesticide use will be preferred among those considered for participation over the three years of the study.
A survey was created using Qualtrics that explored how farmers whose crops would benefit from buzz pollination meet their pollination needs, and was sent to over 500 farmers from Connecticut, Massachusetts, and Rhode Island. We received 97 responses, from which we were able to attain agreements from six farmers to participate in our research by allowing our team to establish pollinator habitats on their farms. In addition, 33 farmers indicated they would be willing to participate in educational programs once we complete our research.
Education & Outreach Activities and Participation Summary