Native Plant Conservation Strips for Sustainable Pollination and Pest Control in Fruit Crops

Native Plant Conservation Strips for Sustainable Pollination and Pest Control in Fruit Crops

Summary

In spring 2010, the beginning of the second year of this project, we re-sowed seeds from the same mix of perennial wildflowers from the first year in order to increase the density of flowers in our flowering plots (Table 1). We sampled beneficial and pest insects within crop fields adjacent to the flower plots and those without flowering plots, finding significantly more beneficial insects in blueberry fields adjacent to wildflower plantings than those adjacent to control areas. We can now compare the density and diversity of beneficial insects collected this year to the background abundance and diversity of beneficial and pest insects found in 2009 when the flowering plots had not been established. In order to determine the effects of flower plots on pollination, we also sampled insects in the flowering plots, observed pollinators in the crop fields during bloom, and measured fruit yield in crop fields adjacent to the flower plots and those without flowering plots. We found no significant difference in pollination of blueberry fields across the treatments, but we did find significantly higher numbers of native bees in fields adjacent to wildflower plantings.

In order to improve grower knowledge of beneficial insect identification and supporting those insects with the use of flowering plots, we held two field days this summer. At the field days we invited growers, extension agents, government employees, and anyone interested beneficial insect conservation to come learn about our project. We also gave out information to attendees on how to set up wildflower plantings and the governmental programs available to growers to help with establishment and maintenance costs of these plantings. The project team surveyed growers in attendance at the field days before and after the meetings, finding that their level of knowledge of conservation practices for building biodiversity in fruit farms increased after the training.

Objectives/Performance Targets

This research project has four main objectives: 1) increase pollination and reduce pest abundance in fruit crops by deploying native plant conservation strips to support native bees and natural enemies, 2) increase producer and public awareness of using flowering plant diversity in farms to support beneficial insects including natural enemies and pollinators, 3) improve producer knowledge of beneficial insect identification and biology, and 4) develop guidelines for increased implementation of insect conservation strips in farmland.

Accomplishments/Milestones

Recent research at Michigan State University has identified and measured the relative attractiveness of native mid-western perennial flowering plants that can provide season-long floral resources for beneficial insects in agricultural landscapes. From their results, we have selected a set of herbaceous flowering plants that rank highly for their attractiveness to natural enemies and pollinators, and are listed under the Conservation Reserve Program – State Acres For Wildlife Enhancement (Table 1). Wildflower seeds were initially sown in early spring 2009 into plots that were prepared in fall 2008 adjacent to the crop fields. During spring 2010, the beginning of the second year of this project, we re-sowed seeds from the same mix of perennial wildflowers as in 2009 to increase the density of flowers in the conservation plots. Grower cooperators were advised to mow their wildflower plots once a month during both years (alternating mowing half of the plot each month during 2010) to control annual weed growth and facilitate perennial wildflower establishment. During 2010 we had an increase in vegetative and flower growth compared to 2009 (Figure 1).

To determine whether conservation strips lead to improved pollination within adjacent fields compared to fields without this treatment, components of crop yield and the bee community were sampled in all fields involved in this project. Observations were made at each of the crop fields adjacent to the flowering and control strips, recording the identity and number of flower-visiting insects (bees, flies, wasps, etc.). From these samples, we observed more native, non-honey bee insect pollinators visiting flowers adjacent to wildflower plots compared to fields adjacent to control plots (Figure 2). Although the majority of pollinators visiting crop flowers were honey bees, there was a diverse group of non-honey bee insect pollinators observed as well (Figure 3). We further assessed abundance and diversity of pollinators in the crop fields during bloom through vacuum sampling using a modified reversed-flow leaf blower. Collected insects from each subsample were placed in plastic bags, labeled, placed into a cooler in the field, and then stored in the freezer for later identification. Sample sorting and analysis for this is still ongoing.

To measure pollination levels in each of the three fruits studied (blueberry, apple, and cherry), flower clusters were tagged, counted, and then covered with a fine nylon mesh bag to exclude insect pollination. After bloom the number of fruit per bagged and open clusters were counted to determine percent fruit set. At the blueberry sites, prior to harvest, fruit from tagged clusters from each of the five blueberry bushes at each location were collected and weighed to determine average fruit weight, and the number of mature and immature seeds were counted as a measure of pollination success. As of the second year of this project, there is no significant difference in pollination between fields adjacent to flower plots and fields adjacent to control plots (Figure 4). This was expected since it takes years for flower plots to establish and subsequently years for native bees to inhabit those areas.
Un-baited yellow sticky traps were deployed from May through September 2010 for one week during each month to determine the abundance and diversity of native bees, insect natural enemies, and common pest insects. At each of our study fields (n=11), 4 traps were placed at four locations; along the crop field perimeter adjacent to the wildflower strip, 15m into the field adjacent to the strip, along the field perimeter of a control field, and 15m into the field along the control. Sample sorting and analysis for this is still ongoing. The abundance and diversity of beneficial and pest insects were also determined in the fruit crops using observational samples taken every two weeks from June through September. Significantly more natural enemies per observed blueberry bush were recorded in fields adjacent to wildflower plots (Figure 5). The composition of the top fifteen most abundant natural enemies observed in blueberry fields can be seen below in Figure 6.
Insects that may be considered pests to crop fields showed a trend that was opposite of that for beneficial insects, with more pests being observed in fields adjacent to control perimeters (Figure 7). Although this increase in pests in fields adjacent to control plots is not significant, it is an interesting finding that gives us hope for future seasons. Abundance and composition of the observed pests can be seen below in Figure 8.
Although not part of the objectives, we also compared the abundance of beneficial insects at organic blueberry farms with those at conventional blueberry farms. We found that in general, organic blueberry farms have significantly higher numbers of beneficial insects in their crop fields than conventional blueberry farms (Figure 9).

We also measured the abundance of beneficial insects within wildflower plots and unplanted control field perimeters, by vacuum sampling once a month, for five, 30-second samples. Sampling was focused on flowering regions of the wildflower plots and the mown areas in the control strips. Collected beneficial and pest insects from each subsample were placed in plastic bags, labeled, placed into a cooler in the field, and then stored in the freezer for later identification. Natural enemies, bees, and pest insects will be identified to major taxonomic groups and quantified in the laboratory for subsequent diversity and abundance analysis. Sample sorting and data analysis are in progress.

In order to improve producer and public awareness of using flowering plant diversity in farms to conserve beneficial insects including natural enemies and pollinators, we helped to organize two field days this summer – one in Sutton’s Bay, MI and one in Fennville, MI (Figure 10 – not included due to human subjects). Grower collaborators, other growers, extension agents, government employees, and anyone interested in beneficial insect conservation were invited to the events to come learn about beneficial insects from a wildflower expert, NRCS and FSA staff, Dr. Rufus Isaacs, and his graduate student, Brett Blaauw. We also gave out information to attendees on how to establish and maintain wildflower plantings and the government programs available to growers to help with establishment and maintenance costs of these plantings (Figures 11 and 12). We also handed out information on current data and results that help advocate for the use of such beneficial insect conservation practices (Figures 13 and 14). During these meetings, we surveyed growers in attendance to determine their level of knowledge on current practices and government programs that are designed to help support beneficial insects in agricultural settings. For example, last year we found that 17-33% of the attendees were receiving FSA or NRCS funding, while this year we found that 30-40% of attendees were receiving this funding (Table 2).

In order to improve grower knowledge of beneficial insect identification and supporting those insects with the use of flowering plots, at the two field days this summer (described above) we also handed out identification pamphlets that helped describe and identify common beneficial insects (Figures 15 and 16). To further help improve growers’ ability to identify beneficial insects, we also went over the identification pamphlets, describing and presenting the attendees with actual specimen of the insects in their handouts. We also surveyed growers in attendance of the field days before and after the meetings to determine their level of knowledge of conservation practices for building biodiversity in fruit farms before and what they were able to learn from the meeting. After the meetings, attendees were 15-20% more likely to correctly identify beneficial insects (Table 3).

In order to develop guidelines for increased implementation of insect conservation strips in farmland we have taken extensive notes on the processes used in establishing the wildflower plots at our farm sites. We talked with our seed provider and other experts to determine which flower species were the most likely to germinate the first year and we sampled all the farm sites to measure which species did indeed germinate. After the first year we were advised to increase our seeding rate in order to increase flower abundance in our plots. Information such as that is important to make sure that the project is not only affordable, but that there are also enough flowers to attract and conserve the beneficial insects. Also, to make sure our guidelines remain affordable for growers we also distributed information packets to our growers that contained sheets for them to fill out on how much of their time and money was put into helping us establish the flower strips.

• Figure 2. Comparison of observed non-honey bee insect pollinators in blueberry fields adjacent to control plots and fields adjacent to wildflower plots during bloom, May 2009 and 2010.
• Figure 3. Total abundance and diversity of insect pollinators combined from 20, fifteen-minute observations taken over a one-week period during bloom from 5 blueberry research fields (Total insects observed = 825).
• Figure 5. Comparison of observed insect natural enemies in blueberry fields adjacent to control plots and fields adjacent to wildflower plots during 2010. Significantly more natural enemies were observed in fields adjacent to wildflower plots (ANOVA, F1,1798 = 7.4, p = 0.0065). Bars represent standard error.
• Figure 11. Page 1 of an information pamphlet provided at local conferences, which summarizes our project.
• Table 1.
• Figure 1. Example of a wildflower strip adjacent to a blueberry field; comparing the flowering plant densities of May 2009 to 2010 and July 2009 to 2010.
• Figure 4. Comparisons of the differences between open and closed clusters of blueberry flowers for (I) average percent fruit set(F = 0.28, p = 0.59), (II) berry weight (F = 0.15, p = 0.69), and (III) and number of mature seeds in fields adjacent to wildflower plots and fields adjacent to control plots (F = 0.0013, p = 0.97). Bars represent standard error.
• Figure 6. Total abundance and diversity of the fifteen most common insect natural enemies combined from 1800 one-minute observations taken over a five-month period in our 5 blueberry research fields (Total insects observed = 2,014).
• Figure 8. Total abundance and diversity of the fifteen most commonly observed blueberry pest insects combined from 1800 one-minute observations taken over a five-month period in our 5 blueberry research fields (Total insects observed = 845).
• Figure 9. Comparison of observed beneficial insects in conventional and organic blueberry fields adjacent to control plots and fields adjacent to wildflower plots over a 10 week period in 2010. There was not a significant difference between treatments (control and flower) for either farming technique, but within each treatment there was a significant increase in the number of beneficial insects observed in organic fields compared to conventional fields (Control, ANOVA, F1,898 = 78.7, p < 0.0001; Flower, ANOVA, F1,898 = 64.8, p < 0.0001). Bars represent standard error.
• Figure 12. Page 2 of an information pamphlet provided at local conferences, which summarizes our project.
• Figure 13. Page 1 of an information pamphlet provided at the 2010 summer field days, which summarizes some of the early data from our project.
• Figure 14. Page 2 of an information pamphlet provided at the 2010 summer field days, which summarizes some of the early data from our project.
• Figure 15. Side 1 of a beneficial insect guide and information pamphlet provided to growers at the 2010 summer field days, which will help growers identify beneficial insects in their fields.
• Figure 16. Side 2 of a beneficial insect guide and information pamphlet provided to growers at the 2010 summer field days, which will help growers identify beneficial insects in their fields.
• Table 3. Questionnaire results taken at the 2010 summer field days showing an increase in ability of participants to correctly identify beneficial insects.
• Figure 7. Comparison of observed insect pests in blueberry fields adjacent to control plots and fields adjacent to wildflower plots during 2010. There was not a significant difference in the number of insect pests found in fields adjacent to wildflower plots (ANOVA, F1,1798 = 1.45, p = 0.23). Bars represent standard error.
• Table 2. Summary of second year questionnaire results taken at the 2010 summer field days.

Impacts and Contributions/Outcomes

The information gathered during the first year of our multi-year project had been primarily baseline and establishment data. After completing year two of this project and flowers grow in the wildflower plots, we now have data and results that appear to support our objectives. We have not increased pollination and hence no increase in fruit yields at test sites, but have managed to increase beneficial insects in fields adjacent to wildflower plots. This year we also kept up good relationships and communication with our grower cooperators, re-sown wildflower seeds at the farms, and distributed information about our project and its objectives to local growers and the public through presentations and informational handouts.

This coming year, 2011, will be an exciting year for our project because we expect to see more flowers bloom in our conservation strips, and hence more data and information to share with the growers and the public. We are also planning an internet-based information outlet that will share the current state of our project, as well as videos, pictures, and links to pertinent and related information.

Collaborators: