Using cultivar mixtures to improve pest control and grain crop production
Recent ecological research and our preliminary data indicate that intraspecific genetic diversity can be quite valuable for suppressing pest populations and improving primary productivity. Unfortunately, most fields planted with modern crop varieties harbor very little genetic diversity. Our integrated research and education project will demonstrate the pest-management potential of genotypically diverse cultivar mixtures to better resist populations of plant pathogens, insect herbivores, and even weeds to improve crop productivity. Moreover, because cultivar mixtures tend to improve yield over monocultures even in absence of pests, our work will also demonstrate general improvements in crop productivity by increasing genotypic diversity. Using field experiments at two research centers and farms of three cooperating growers, we will demonstrate and quantify production benefits of planting fields containing several different varieties of wheat. At all these sites, we will compare insect, pathogen, and weed populations and yield among cultivar mixtures and the constituent monocultures.
Thirty conventional and organic farmers will adopt mixtures on at least 300 acres (ten acres per grower) of small grains to decrease insect, disease, and weed problems and improve production. By employing mixtures, growers will increase yield at least 5% compared to typical monoculture yield monocultures, meaning yield increases per acre will range between 2.5 bushels per acre for organic growers that typically yield 50 bu/acre to 4 bu/acre for conventional growers who average 80 bu/acre. Conventional growers will also reduce pesticides costs by $20 per acre, which represents nearly 50% savings on a typical preventative pesticide program that costs approximately $37 per acre, further improving profitability.
1. Through winter meetings (in-person and webinars) and summer field days, 1500 farmers will be exposed to the idea of cultivar mixtures and learn of the yield and pest management benefits of mixing cultivars together. These farmers will receive evaluations to capture the state of their knowledge before and after presentations, and their interest in learning more about farming with cultivar mixtures. Growers with interest will be asked for their contact information (November 2012-March 2013 & November 2013-March 2014).
Milestone 1, associated accomplishments: This milestone is in progress, but for the 2012-2013 season we exposed to our work with cultivar mixtures at least 1094 growers at 19 separate presentations. In 2013-2014, we presented the concept and some research results to an additional 930 farmers at 16 extension meetings. Evaluations revealed that few growers had been exposed previously to cultivar mixtures, unfortunately, very few were willing to share their contact information with us. For growers approached in 2012-2013, many liked the idea, but were not willing to tcommit to the idea until we had some performance/yield data to share. Even though we had promising yield data from 2012-2013, we still did not have good success in the 2013-2014 extension season. Growers acknowledged the potential benefits but focused on potential logistical challenges associated with buying different varieties of seeds and planting a mixture. They were concerned that mixtures could complicate the timing of fungicides if they were necessary. Fungicides are usually applied at flowering, and growers felt having more than one wheat variety would widen the flowering window too much, making a target fungicide application difficult.
2. One-hundred-fifty growers expressing interest in learning more about cultivar mixtures will be surveyed to characterize their concerns about and expectations for cultivar mixtures (November 2012-March 2013 & November 2013-March 2014).
Milestone 2, associated accomplishments: We have been unable to survey growers due to a lack of contact information—too few growers expressed an interested in cultivar mixtures. Nevertheless at our project specific field days, we have engaged growers in frank discussions about benefits and limitations of growing cultivar mixtures. In 2013-2014, we addressed these limitations head on at field days, but still encountered wide spread hesitancy about growing more than one varieties of wheat together. We were unable to gather enough contact information to survey.
3. Fifty of these growers will attend field days featuring the benefits of cultivar mixtures. Portions of these sessions will specifically address the concerns raised by growers in the survey (April-July 2013, April-July 2014).
Milestone 3, associated accomplishments: We held field walks at two of our cooperating farms, attracting 63 agricultural professionals to learn about cultivar mixtures first hand. In 2013, We also had field days at our research farms, attracting an additional 260 growers that heard about cultivar mixtures. In 2014, we had two additional field days with 105 attendees. In these presentations, we addressed growers concerns and addressed them with in-depth discussions.
4. Thirty of these growers will trial cultivar mixtures on their farms, and many will share their experiences with other growers via in-person presentations, webinars, podcasts, and newsletters (October 2013 to end of project and beyond).
Milestone 4, associated accomplishments: We have succeeded in getting four growers to trial mixtures. This is clearly insufficient but it is the best we have accomplished so far. Growers just seem reluctant to complicate their farming practices, even though we can point to production and pest management benefits. We will continue to beat the bushes in 2014 to try to get more growers to try cultivar mixtures.
Impacts and Contributions/Outcomes
As in the previous year, our research plots for 2013-2014 were planted at farms of three farmer collaborators (Mertztown and Holtwood, PA, and Clear Spring, MD) and two Penn State research farms (Centre and Lancaster Counties, PA). We are currently in process of sorting the insect samples and are waiting on analytical results for the disease samples. For each site, we sampled insect populations, gauged the activity of the natural enemy populations in each plot at each site, assessed diseases attacking the leaves and grain head, and sent grain samples to an analytical lab to measure amounts of mycotoxins present. We are currently conducting these analyses and have nothing yet to report.
For yield at the various sites/plots, we found that mixtures can compete with the yields of the best yielding varieties. In 2012-2013, we found that mixtures of wheat grown in eighth-acre plots on commercial farms improved yield by 6% over monocultures, whereas yields of mixtures and monocultures in small plots on our research farms were equivalent. In 2013-2014, yields of mixtures and monocultures on the three commercial farms were equivalent as were yields of the two treatments from our research farms. These results strongly suggest that mixtures do not impose a yield drag on wheat production in our region. Given the potential pest management benefits, we see advantages that can be provided by mixtures of wheat even in the absence of a yield advantage, which we detect in the first year of our study but not the second.