Evaluation of Plant Composition and Strip Size on the Effectiveness of Native Plant Conservation Strips for Sustainable Enhancement of Beneficial Insect Communities
The goal of this project is to determined the response of beneficial insects and their ecosystem services to the size of wildflower plots. In 2009 we established twelve wildflower species native to Michigan in plots ranging from 1-100 m2, and we sampled these plots for beneficial insects in 2010 and 2011. Similarly to the 2010 data, in the 2011 growing season we found that densities of both insect natural enemies and pollinators increase with wildflower plot size. In the size plot treatments we also measured the effect of flower plot size on the biocontrol of sentinel corn earworm eggs. Although not statistically significant, we did find a trend that biocontrol of eggs increased with the increase in plot size. In terms of pollinators, we also found that the abundance of native bees and pollination of native flowers both increase with the increase of wildflower plantings. As a way of increasing exposure of our project and spreading information and sources on insect conservation, we presented at numerous extension meetings and conferences and created a project sign and displayed it near the wildflower plots at the Trevor Nichols Research Center (Figure 9). We also had an article featured in the January issue of the Fruit Growers News – <http://fruitgrowersnews.com/index.php/magazine/article/using-habitat-to-increase-pollination/> – that gave a brief description of our project and how to conserve pollinators using wildflower plantings.
This research project has three main objectives: 1) determine whether native flowering plots composed of a mixture of annual and perennial wildflowers will support beneficial insects earlier and remain established longer than those strips composed of only perennial or annual wildflowers, 2) determine the response of beneficial insects to the size of wildflower plots, and 3) use our results to increase producer and public awareness of using native flowering plants to support beneficial insects in farmland.
During 2010 only the buckwheat bloomed and in 2011 we had very few native plants even grow. These flower plantings were flooded early in the season and later in the season became overrun with weeds (Figure 1). We attempted to control the weeds, but we still had very poor germination of the native wildflowers. Unfortunately, we were unable to sample these plots during the 2011 growing season.
In 2009 we established 25 wildflower plots of five replicated sizes of 1, 3, 10, 30, and 100 m2. In 2011 we also completed an experiment to measure the affect of wildflower plot size on pollinators and the subsequent pollination of wildflowers. To determine how insect pollinators respond to wildflower plot size we performed 5 minute timed observations of 1 m2 areas for each of the 25 wildflower plots. During these observations we identified all insects to family that were observed visiting wildflowers within the 1 m2 areas. This sampling was done on calm, warm, and sunny days once a month for June, July, August, and September. We observed a diverse community of non-bee beneficial insects visiting wildflowers in the different sized plots, with hoverflies composing 60% of those observed (Figure 3). While the non-native honey bee was the most common type of bee we observed visiting wildflowers, we also observed a diverse group of native bees, especially bumble bees, visiting those flowers as well (Figure 4). We also used sweep net sampling to collect specimens in order to identify pollinators to species to see if there is a species response to wildflower plot size. During the same timed period as the observations, but on a different day, we sampled each of the 25 plots for a timed period of 10 minutes, collecting any bee observed visiting flowers in the entire plot. We found that native bee abundance significantly increases with wildflower plot size (Figure 8), but we are still working on identifying collected specimens to species.
In 2010 we completed an experiment to measure the effect of wildflower planting size on the biological control of soybean aphids. During June, July, and August of 2011 we repeated this experiment using corn earworm eggs, which involves a less intensive protocol since we did not need to worry about keeping an aphid colony alive and growing hundreds of soybean plants. The eggs were glued onto cardstock squares, attached to a 1 m post, and placed near the center of each of the 25 wildflower plantings at TNRC (Figure 5). We measured biological control services by comparing egg damage/removal before being placed into the field with the egg damage/removal after being in the field exposed to natural enemies for four days. The number of damaged or missing eggs were used to calculate a Biocontrol Services Index (BSI): see attached image
The resulting BSI ranges from 0-1, with values increasing as the level of predation increases (Gardiner et al. 2009). Here, Ec = the number of eggs in before being placed in the field and Eo = the number of eggs remaining after four days in the field, p = plot, and n = the number of replicates. BSI values were compared among cards placed in the different sized wildflower plantings. In 2010 we found a significant increase of BSI for soybean aphids as wildflower plot size increased. In 2011 using corn earworm eggs we saw a similar trend to the 2010 data, but there was not a statistically significant increase in BSI with plot size (Figure 6).
A new project for the 2011 season, to measure the affect of wildflower plot size on the pollination of wildflowers we selected three flower species that had three different bloom periods; early-season bloom (sand coreopsis), mid-season bloom (cup plant), and late-season bloom (New England aster). At each of the 25 wildflower plots we tagged six unopened flower buds, designating two buds for each of three treatments to test for pollination limitation: restricted pollination, hand pollination and open pollination. To determine if plants could produce viable seeds in the absence of insect visitors, buds tagged for restricted pollination were then enclosed with a fine mesh bag, and remained untreated for the duration of the procedure. Buds designated for hand pollination were also bagged, while those intended for open pollination remained unbagged and untreated. When the flowers began to bloom in the hand pollination treatment, we applied collected pollen to the open flowers using a paintbrush. We carried out hand pollination three times in a span of one week, only unbagging the flowers during the hand-pollination process (Figure 7). After the flowers set seed, each of the six seed heads from each of the 25 plots were then collected and allowed to dry. To determine female reproductive success of the treatments, we opened each bud and recorded the number of viable mature seeds inside. We were then able to compare the increase in pollination due to insect visitation by subtracting the number of mature seeds found in the bagged flowers form the number of mature seeds in the unbagged flowers. We found that for each of the three wildflower species there was an increase in pollination (# of mature seeds) with the increase in wildflower plot size. This trend corresponded to the abundance of native bees visiting flowers during the same time period as the different flowers were in bloom (Figure 8).
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 presented at numerous extension meetings and conferences during the past year. These presentations included information about using wildflower plantings to support beneficial insects and current results from this SARE funded project. The following are the authors, titles of presentations, and the meetings we presented results from this SARE funded project at:
Brett R. Blaauw and Rufus Isaacs. 2011. How does wildflower planting size affect insect pollinators and their delivery of pollination ecosystem services? Entomological Society of America Annual Meeting in Reno, NV. Oral presentation.
Brett R. Blaauw and Rufus Isaacs. 2011. Variation in natural enemies and biological control with the size of native wildflower plantings. Royal Entomological Society – Ento’11 in Chatham, UK. Oral presentation.
Brett R. Blaauw and Rufus Isaacs. 2011. Response of natural enemies and their ecosystem services to wildflower planting size. Michigan State University – Graduate Academic Conference in East Lansing, MI. Poster presentation.
Brett R. Blaauw and Rufus Isaacs. 2011. Response of natural enemies and their ecosystem services to wildflower planting size. Plant Science Graduate Student Research Symposium at Michigan State University in East Lansing, MI. Poster presentation.
Brett R. Blaauw and Rufus Isaacs. 2011. Response of natural enemies and their ecosystem services to wildflower patch size. Entomological Society of America – North Central Branch Annual Meeting in Minneapolis, MN. Oral presentation.
Brett R. Blaauw and Rufus Isaacs. 2011. Enhancing Natural Enemies in Crops Using Flowering Plants. Great Lakes Fruit, Vegetable and Farm Market EXPO in Grand Rapids, MI. Invited oral presentation.
Brett R. Blaauw and Rufus Isaacs. 2011. Conserving Native Bees in Blueberry and Other Small Fruit. Great Lakes Fruit, Vegetable and Farm Market EXPO in Grand Rapids, MI. Invited oral presentation.
Brett R. Blaauw and Rufus Isaacs. 2012. The use of wildflower plantings to conserve beneficial insects in Michigan tree fruit. Northwest Michigan Orchard and Vineyard Show, Acme, MI.
Brett R. Blaauw and Rufus Isaacs. 2012. The effect of native wildflower planting size on beneficial insects and their ecosystem services. Science, Practice & Art of Restoring Ecosystems Conference, East Lansing, MI.
- Figure 6. Biocontrol services index (mean ± SEM) of corn earworm eggs for the different sized wildflower plots.
- Figure 8. Comparison of bloom period, abundance of native bees observed during that period, and the mature seed count among different sized wildflower plots for three native flowers; sand coreopsis, cup plant, and New England aster.
- Figure 2. A.) An aerial photograph of the wildflower plantings at the Trevor Nichols Research Center showing the different sizes, 2010. B.) Ground level photographs of the different sized flower plots, 2010.
- Figure 3. The beneficial insect community of the top ten most abundant non-bee beneficial insects observed visiting wildflowers (N=782).
- Figure 1. Example of annual wildflower plot that did not establish.
- Figure 5. The setup for measuring biocontrol services of sentinel corn earworm eggs. Eggs were glued to a piece of cardstock and then placed in the middle of the wildflower plantings.
- Figure 7. Visualization of techniques used to measure pollination within the different sized wildflower plantings.
- BSI Equation
- Figure 4. The total bee community observed visiting wildflowers (N=673).
Impacts and Contributions/Outcomes
As a way of increasing exposure of our project and spreading information and sources on insect conservation, we created a project sign and displayed it near the wildflower plots at the Trevor Nichols Research Center (Figure 9). We also had an article featured in the January issue of the Fruit Growers News – <http://fruitgrowersnews.com/index.php/magazine/article/using-habitat-to-increase-pollination/> – that gave a brief description of our project and how to conserve pollinators using wildflower plantings.
The second year of this project was very productive. We took numerous photographs of the flower plots over time (e.g. Figure 2B; more seen here <https://www.msu.edu/~blaauwb1/Main.html>), as well as of the insects that visited the flowers in the plots (Figure 10). Despite the problems we had with the flower plots in Objective 1, we were able to successfully measure biocontrol and pollination services in wildflower plots for Objective 2. We found that the abundance of native bees and pollination of native flowers both increase with the increase of wildflower plantings (Figure 8).
Results from the 2010 season of this project, Response of Natural Enemies and Their Ecosystem Services to Wildflower Planting Size (Figure 11), were presented at the 2011 Graduate Academic Conference and the 2011 Plant Science Graduate Student Research Symposium at Michigan State University in East Lansing, MI. The poster was awarded second prize at the Plant Science Graduate Student Research Symposium.
- Figure 9. Example of an informational project sign placed at wildflower plantings and designed as an introduction to the project for visitors to Michigan State University’s Trevor Nichols Research Center.
- Figure 11. Poster presented at the 2011 Graduate Academic Conference and the 2011 Plant Science Graduate Student Research Symposium at Michigan State University in East Lansing, MI.
- Figure 10. Examples of beneficial insects observed visiting wildflowers in the size plots at Trevor Nichols Research Center. A.) a carpenter bee on New England aster, B.) a wasp feeding on stiff golden rod flowers, C.) a hoverfly visiting a sand coreopsis flower, and D.) a green lacewing feeding on boneset flowers.
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