Exploring relationships between pollinators and canola on the Palouse

Progress report for SW18-031

Project Type: Research and Education
Funds awarded in 2018: $207,134.00
Projected End Date: 03/31/2022
Grant Recipient: Washington State University
Region: Western
State: Washington
Principal Investigator:
Dr. David Crowder
Washington State University
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Project Information


Canola is an increasingly common crop grown on the Palouse due to its potential for producing biofuels and to diversity conventional cereal-legume rotations. Our preliminary data suggest that canola crops, which provide a large source of pollen and nectar in an otherwise simple floral landscape, support a diverse population of honeybees and native species including bumblebees, mason bees, and sweat bees. However, while many canola fields are surrounded exclusively by agriculture, others are near sizeable tracts of prairie and other insect-friendly habitat. Importantly, canola yields appear to increase at sites surrounded by more natural habitat, possibly due to increased bee abundance in these landscapes. Our preliminary data suggest two main hypotheses that warrant further investigation. First, increasing natural habitat surrounding canola fields promotes increased bee abundance and seed yields. Second, increasing nectar sugar content is attractive to bees and promotes high canola yields. Our project addresses these knowledge gaps, allowing our team to gain a better understanding of the role of pollinators in promoting high yielding and high quality canola plants. We will also determine how growers might be able to modify their management practices to promote high pollinator activity on their fields. This will improve the sustainability of canola producers in the Palouse. Our project thus meets several goals of the Western SARE program: (1) promote good stewardship of the nation’s natural resources (by providing information on how growers can modify farming practices to promote pollinator diversity and high yielding/quality canola); (2) promote crop, livestock, and enterprise diversification (our project will aid growers in incorporating canola into rotations, which will increase their enterprise diversity; our project also explores diversity of pollinators); and (3) examine the environmental implications of adopting sustainable agriculture practices and systems (by exploring how farming practices affect pollinators and the quality of canola plants).

Project Objectives:

(1) Explore relationships between landscape structure, bees, and canola yields and quality
(2) Determine how farm management practices affect nectar and pollen traits
(3) Educate growers on pollinator management in canola


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Studies suggest that yields and quality of canola increase when considerable natural habitat surrounds fields, potentially due to increased bee abundance in such landscapes. We hypothesize that in diverse landscapes with abundant wild bee populations, canola producers might be less reliant on honeybees while to meeting the pollination goals. By sampling canola fields throughout the Palouse region, our project will gather important baseline data on the abundance and diversity of wild bee populations in the Palouse across landscapes of varying diversity.

Our data also suggest that canola flowers with high sugar content attract bees, which leads to higher yields. Other traits, however, such as protein content of pollen and flower size might also be important for attracting bees into canola fields. Given that the Palouse is a highly fragmented matrix with many crop fields and little natural habitat, growing highly attractive canola is critical to attract bees that might have to forage over long distances. Growers would benefit from a better understanding of how they can promote these desirable traits on their fields. We hypothesize that floral/nectar/pollen traits can be influenced by a myriad of factors including crop variety, crop rotation, and soil quality.

Materials and methods:

Objective 1 - Explore relationships between landscape context, bees, and canola yields

Exploring pollinator communities in canola across variable landscapes. Working with a network of grower cooperators, in each year (2018 to 2020) we will locate 8 winter canola and 8 spring canola fields to sample, each separated by at least 2km to ensure independence. Co-PI Sowers, the lead for extension on the project, maintains active relationships with most canola producers in Washington and Idaho. Sowers will thus facilitate the selection of farm sites and cooperators once the project begins. In each year, each field will be sampled once using bee bowls filled with soapy water that attract bees and blue vane traps that sample larger bees. Traps will be deployed early in the morning on sunny days along the edge of a canola field and left for 24h. From the samples, we will identify all bees collected and determine the abundance of each species and the diversity (# of species) of the overall community. We will also collect landscape and weather data around sites. Landscape data come from USDA Cropland Datalayer maps that identify all habitats in the US at a 30m resolution. Weather data, including temperature and wind, will be from the National Oceanic and Atmospheric Administration. Data on yield and crop quality will be obtained directly from growers at the end of each field season.

We will analyze bee abundance and richness using linear models with field size, natural habitat, temperature, and wind on the sample day as explanatory variables (field size, temperature, and wind are covariates). In our initial analyses, we will categorize landscapes based on a simple metric of the percentage of “natural habitat” (which in our region largely consists of remnant prairie or shrub-steppe habitat). This metric has been widely used in studies of landscape effects on bees. If our hypothesis is correct, we should see an increase in bee abundance and diversity with more natural habitat. Follow-up analyses will attempt to identify specific habitat features (such as the acreage of prairie, or the acreage of canola within the broader landscape) that promote abundant and diverse bee populations. We will then analyze canola yields and quality using linear models as a function of bee abundance, natural habitat, and the interaction between these variables. Variety will be included as a covariate. We will also explore the distance over which specific habitats act as sources of bees into canola. These analyses should confirm whether bee abundance and landscape context affects yield and quality of winter and spring canola.

Objective 2 – Determine how farm management practices affect nectar and pollen traits

On each farm from Objective 1, we will sample floral traits that are important in attracting bees to canola fields. These data will be collected once per year during peak bloom from 20 canola plants per field. The variables we will measure include: (1) nectar sugar content; (2) nectar volume; (3) number of flowers; (4) flower size; and (5) protein content of pollen. We will measure nectar secretion rates by sampling nectar from flowers of the same age during peak bloom to control for age-related variation. Plants will be inspected daily to record the day upon which each flower opens. Daily, petals of all open flowers will be marked with a permanent marker to ensure that older flowers are not used. Plants will be visited 24hr later, and nectar will be removed from any flowers that had opened since the previous day by draining the inner nectaries using microcapillary tubes. Nectar production will be quantified from the inner (lateral) nectaries only. One sample of nectar per plant will be used for analysis, comprised of nectar collected from 5 flowers that had been drained 24hr previously. Microcapillary tubes will be immediately stored in 1.5mL Eppendorf tubs and then transferred to a freezer set at −20°C. To determine 24hr nectar secretion rate, the length of the column of nectar in the microcapillary tube will be divided by the number of flowers sampled to yield mean volume (μL) per flower.

We will assess nectar quality by separating mono and di-saccharide sugars with ultra-performance liquid chromatography on a Luna amide column. Sugars will be quantified with an evaporative light scattering detector and the concentration of each will be calculated using an internal standard and a series of external standards. Similarly, amino acid components will be determined using AccQ•Tag derivation and UV detection.

Towards the end of the growing season, seed pods will be harvested just before ripening to avoid loss of seeds. After all pods have been harvested, we will score the total number of pods per plant and weight of seeds (g/plant). Remaining aboveground plant biomass will then be harvested, dried at 70°C for at least 48hr, and weighed. Finally, we will also analyze the oil and chlorophyll contents of seeds using standard techniques for evaluating the market price of the resulting oilseed crop. Working with growers, we will also collect data on various management practices from each farm, including: (1) canola variety; (2) Round-up Ready/not; (3) neonicotinoid use; (4) diversity of crop rotation; and (5) soil traits (pH, organic matter, nutrient levels, microbial biomass – each of these soil conditions can affect plant performance and floral/nectar/pollen).

We will complement our open field surveys with an experimental evaluation of floral traits across different winter and spring canola varieties. Currently, there are ongoing open-field trials to evaluate the yield potential of multiple winter and spring canola varieties on the Palouse. These “variety trials” have been replicated in large-scale plots across multiple locations in the Palouse, including the farms of our three cooperating producers, who will continue to allow the usage of their farms throughout the course of this study. We will sample floral traits from 20 canola plants from 6 winter and 6 spring canola varieties – these traits will be sampled from each of three unique locations where variety trials have been set up in each year (these farms have already been identified, and the cooperating producers listed on the proposal will manage these trials).

We will complement our sampling of floral traits by assessing rates of pollinator visitation to each of the spring and winter canola varieties. On four separate occasions throughout bloom (twice in spring canola and twice in winter canola), we will monitor focal plants in the variety trials for pollinator visits. During each observation bout, pollinators will be observed for 10 min to record the number of unique pollinators that visit 10 canola plants in each plot from the variety trials (6 varieties × 4 plots per variety × 10 min = 240 minutes of observations [4:00] in each day in each field). We will characterize pollinator visitation rates by averaging the number of bees for each experimental plot. For analyses, we will use the average number of counted flowers per plant per counting event to standardize across plants with variation in flower number.

We will analyze floral traits using linear models with management variables and landscape context as explanatory variables. This will allow us to determine specific management practices that promote desirable floral traits. We expect the diversity of the crop rotation and soil traits to strongly influence floral and nectar traits of canola, and we also expect to determine the attractiveness of different canola varieties. We will then analyze the richness and abundance of bees as a function of these floral traits. We expect that fields with more desirable traits will attract a greater abundance and diversity of bees, which will promote high yields and quality.

We will use ANOVA to determine if floral traits differ between the canola varieties. Field will be included in all analyses as a random variable (to control for variation across the farms where variety trails will be conducted), and separate analyses will be conducted for both spring and winter canola. We will also use ANOVA to determine if rates of pollinator visitation (which is a proxy for pollination services) are affected by canola variety. These trials will determine varieties that are naturally most attractive for pollinators, and identify the mechanisms (i.e., increased nectar sugar content) that cause the difference in attractiveness.

Objective 3 - Educate growers on pollinator management in canola

(A) Field tours - Each year our team will participate in 6-8 “canola field tours”, where we talk to producers about pollinator conservation and the role of pollinators for canola crops. However, we have found that producers are more likely to attend field days if they are given information on many subjects (i.e., agronomics, soil fertility, pest management). We will work with other research and extension scientists working in canola at WSU to develop a broad program for each field day, presenting information across these diverse subjects. While one of our main goals is to spread information on pollinators, by developing a broad agenda for each field day will allow us to attract more producers.

In each year of the project, we will conduct 3-4 field tours on farms with spring canola, and 3-4 field tours on farms with winter canola. This will allow us to capture variation among these crop types, while also allowing us to attract a broader group of interested stakeholders. Field tours will be spread across a broad geographic area, and spaced out in time as much as possible, to ensure that we reach as many producers as we can.

(B) “Stop and Talk” Events – One innovative format that we will include in our outreach involves “Stop and Talk” events. We will encourage canola producers to directly contact our project team if they have important and time-sensitive issues related to their production of canola, particularly issues related to pollinators, integrated pest management, or integrated pollinator management. After speaking to producers on the phone, we will attempt to arrange a site visit within a week after the call, and we will invite neighboring farmers to join us. During these site visits we will scout the canola field and help assess and mitigate their production challenges. Co-PI Sowers has found that growers respond well to personalized visits to their farms, and learn well when they are interacting not only with researchers and extension agents but also their farming peers (i.e., neighboring producers). As canola is a growing crop, building a network of producers that our team regularly interacts with will be a major boon for extension as canola acreage continues to expand on the Palouse.

(C) Extension bulletins – We will prepare a bulletin on pollinators on canola crops to serve as an identification guide and as a guide for pollinator management. Currently, the US Canola Association’s Grower’s Manual does not have any information on the management of pollinator populations. As one of our grower-collaborator’s (Hennings) sits on the board of the US Canola Association, we will also ensure that our bulletin is widely shared through their website to ensure it reaches as many producers as possible. Bulletins will also be published to the WOCS Website (css.wsu.edu/oilseeds/), the WSU small grains website (smallgrains.wsu.edu), and the Northwest Pollinator Initiative Website (which Crowder maintains, nwpollinators.org). Both Crowder and Sowers are members of the WOCS and “Small Grains Extension Teams” at WSU, and these site serves as a clearinghouse for information for many canola and cereal-legume producers (which is the group we are particularly targeting as potential canola producers). The NW Pollinator Initiative website is maintained by PI Crowder to provide broad information on pollinators in many crops, and is another arena over which we will share our results.

(D) Websites – We will publish data to the WOCS website (css.wsu.edu/oilseeds/), the WSU small grains website (smallgrains.wsu.edu), and the NW Pollinator Initiative Website, which focuses on pollinator conservation in the PNW (nwpollinators.org).

(E) Canola Production Guide – We will incorporate our research into the Pacific Northwest Canola Production Guide by describing pollinator management for canola and the role of integrated farm management for controlling pests without disrupting pollinators. As described above, we also hope to incorporate our results more broadly into the US Canola Association’s Grower Manual to increase dissemination of our results.

(F) Outreach presentations and podcasts – Members of our project team will also share results at academic conferences. In particular, we are targeting the 2018 meeting of the American Society of Agronomy, which is being held in conjunction with the meeting of the US Canola Association. The two lead PIs (Crowder and Sowers) will travel to this meeting along with producers Hennings, Jordan, and Emtman. By attending the meeting as a project team, we hope to interact broadly with other producers and stakeholders to help assess and develop our project to align with national stakeholder needs.

Research results and discussion:

Objectives 1 and 2 - In 2018 we sampled 8 winter and 8 spring canola fields for bees as well as an examination of floral traits of canola. These data were complemented by an addition 8 winter and 11 spring canola fields that were sampled in 2019 (Fig. 1). In 2020 we expanded our geographic range further into Idaho and Washington and Montana, which gave us an even greater representation of the landscapes where canola is produced (Fig. 2). Sites were sampled based on the methodologies described above to collect bees and sample plant traits.

Figure 1. Location of study sites sampled in 2019, along with the typical landscape surrounding each site
Figure 2. Sites sampled over the course of the project from 2018 to 2020.

Data collected from 2020 (and some bees from 2019) are still being evaluated to identify every bee species collected to species; we were limited in our ability to use laboratory resources for multiple months during 2020 due to the COVID-19 pandemic and bee identification and plant processing was delayed considerably. As we collected thousands of bees these data will be completed and analyzed by early 2021, and we expect to complete all of our data analysis by late 2021. Although we cannot complete our analyses until all bees are identified, we have made progress in grouping bees into broader taxonomic groups (genera and/or families). From these data several trends are apparent. First, wild bees are not highly abundant in most canola fields, with densities between 10 and 50 bees collected from our traps (Fig. 3). Some fields, however, supported large numbers of bees (over 750 at one field site). Understanding why populations are so variable will be a key focus on future research.

Figure 3. Abundance of various major bee taxonomic groups across sites in 2019

Second, both nectar sugar concentration, nectar volume, and flower petal size were widely variable among sites, even for sites that grew the same canola variety (Figures 4-6). While we were not able to collect nectar from some sites due to low volume, for sites where we did collect these data both the concentrations and volume varied widely. This variability is interesting because it suggests that farm management practices can produce variable plant traits that are more or less appealing for bees. As with our bee data, in the coming year we will produce additional models to explore the key factors that affect variation in canola floral and nectar traits.

Figure 4. Nectar sugar concentration across farms
Figure 5. Nectar volume across farms
Figure 6. Flower petal size across farms

However, some other trends in the first two years were apparent, and we are continuing to process samples from 2020 now that we are able to fully get back into a safe laboratory space and have hired additional help. First, wild bees appeared to benefit from increased % of natural habitat in the landscape, as expected under our hypotheses. Honey bee abundance did not appear to respond in any meaningful fashion to landscape diversity; this is not surprising as growers stock honey bees on their farm and this largely determines abundance.

We have also completed large greenhouse experiments examining the floral traits of different canola varieties. Again, these data are preliminary and will be complemented by further studies in 2021 (studies were planned in 2020 but we were unable to use our greenhouse facilities to full extent due to the effects of the pandemic). Early data have shown that canola varieties differ in the time to flowering, the length of the bloom period, the number of flowers per plant, the size of flowers, and the nutritional properties of both pollen and nectar. In 2021 we are making a concerted effort to determine the impacts of each of these factors on bee attraction to canola.

Finally, we added an additional data collection objective to the project in 2019 and 2020. We brought in a new postdoctoral scholar, Vera Pfeiffer, who focused on the role of canola in promoting genetic diversity among bumblebees. Vera was able to collect DNA from over 8,000 bumblebees across our sites in 2019 and 2020. These data are currently being analyzed to determine the number of bumblebee colonies per site and their genetic diversity. This will provide a nice complement to our community ecology data and show if certain canola fields support greater bee diversity at the genetic level.

Objective 3 - We have also continued extension efforts in canola. One of the graduate students on the project, Rachel Olsson, has participated in four canola field days in 2019. Postdoc Pfeiffer participated in 3 of these field days. Olsson and Pfeiffer have also participated in our "stop and chat" series, and worked to develop a social media presence related to research on canola. We held four virtual field meetings in 2020 due to our inability to host field days in person. We also published the first extension bulletin on bees in canola crops.

Finally, in 2021 we recruited a new PhD student to the Crowder lab, Salena Helmreich, who will work along our project team in the last year along with Pfeiffer (Olsson graduated in May 2020 with her PhD)

Research conclusions:

Each of the objectives is ongoing and conclusions would be preliminary.

Participation Summary
18 Farmers participating in research


Educational approach:

As described in Objective 3 in the previous section, we are developing a multi-faceted approach to producer and ag-professional education. We will share information with producers and ag-professionals directly (i.e., “where they work”) through our field tours, “Stop and Talk” events, and the WSU-WOCS annual Oilseed Workshops. By hosting 6-8 field tours per year, we hope to attract a diverse audience of producers. For producers and ag-professionals, we will also develop a diversity of written materials. We will publish extension bulletins and a canola production guide as part of the project. Information will also be shared on multiple websites. Finally, we will develop multiple presentations and podcasts to reach growers who best receive information through these means of communication. Presentations and podcasts will be published oo our websites to ensure they are archived for the long-term. Our previous experience has shown that producers often trust the information they receive from other producers or crop consultants more than information from researchers. By directly involving our cooperating producers in our outreach efforts, we hope to limit this potential pitfall and ensure our information is valid and trusted.

 We expect to have a diversity of scholarly publication and educational materials produced as part of the project. As mentioned above, we plan to publish extension bulletins and a canola production guide, which will be published on our websites and widely printed and handed to growers at field tours. We also expect to publish refereed journal articles from research conducted in journals such as Environmental Entomology or Agriculture, Ecosystems, and Environment (both of which often have papers related to sustainable agriculture and entomology). Outputs of the project will also include conference presentations and presentations at the annual meeting of the Washington Canola Association (in January) and the annual WSU-WOCS meeting in Pullman, Washington in early spring. Finally, we will develop 2-3 podcasts each year to provide timely content on issues related to canola production that can be easily downloaded and digested by producers and ag professionals.

Educational & Outreach Activities

10 On-farm demonstrations
1 Published press articles, newsletters
4 Tours
6 Webinars / talks / presentations
8 Workshop field days

Participation Summary:

100 Farmers
100 Ag professionals participated
Education/outreach description:

In 2019 we had 6 on-farm demonstrations, 4 field days, and 2 farm tours where we showcased different canola varieties and discussed the role of pollinators in canola production. This was the same number we had in 2018, and the total numbers across both years are shown above. We estimate that around 100 individuals attended these events in total.

One of the graduate students on the project, Rachel Olsson, produced 3 talks at the WOCS-Canola event and entomological conferences to detail the preliminary stages of the work. We expect to more fully engage in education in year 3 of the project as data continues to be collected, once we are more confident of recommendations for effective canola production.

Learning Outcomes

40 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key areas taught:
  • Canola floral traits
  • Bee biology
  • Pollination ecology
Key changes:
  • Farming practices that support healthy pollinator species without harming yields

Project Outcomes

8 New working collaborations
Project outcomes:

The project is still in it's second year and we haven't completed an evaluation as of yet. These data will be available in 2020.

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.