Using cultivar mixtures to improve pest control and grain crop production

Using cultivar mixtures to improve pest control and grain crop production

Summary

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.

Objectives/Performance Targets

Performance Target:

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.

Milestones

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).

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).

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).

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).

Accomplishments/Milestones

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. In 2014-2015, we raised the issue at seven meeting, reaching 735 growers. 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 commit 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 or 2014-2015 extension season. Growers acknowledged the potential benefits but preferred to focus on potential logistical challenges associated with buying different varieties of seeds and planting a mixture, seeing these issues as unnecessary complications to their operation. Moreover, the majority of growers we reached were conventional (i.e., not organic) farmers and they were concerned that mixtures could complicate the timing of fungicides if they were necessary. Particularly in moist years, fungicides are often applied  by conventional farmers at flowering, and growers felt having more than one wheat variety would widen the flowering window too much, making precisely targeting fungicide applications difficult.

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 at our meetings. Nevertheless at our project specific field days, we engaged growers in frank discussions of the benefits and limitations of growing cultivar mixtures. In 2013-2014 and 2014-2015, 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.

Milestone 3, associated accomplishments: We held field walks at two of our cooperating farms, attracting 63 growers 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. 

Milestone 4, associated accomplishments: We have succeeded in getting six growers to trial mixtures. Despite the our efforts to reach as many wheat growers as possible, too few growers were interested in committing to growing cultivar mixtures on their farms. This is clearly insufficient. Growers just seem reluctant to complicate their farming practices, even though we can point to production and pest management benefits.

Impacts and Contributions/Outcomes

We had no research plots in the ground in 2014-2015, but we wrapped up our research efforts from 2013-2014, when we had plots on three collaborating farms (Mertztown and Holtwood, PA, and Clear Spring, MD) and two Penn State research farms (Centre and Lancaster Counties, PA). In 2015, we finished sorting the previously collected insect samples and are currently conducting statistical analyses of these samples to understand the distribution of pest insects and natural enemies (insects and spiders). We also had our grain samples from the plots on the research farm analyzed for alfatoxins, which can be produced by fungal infections of the grain head (i.e., Fusarium head blight, aka head scab). Fortunately, none of our 130 samples yield any detectable levels of alfatoxins. While it is frustrating that the relevant pathogen did not infest our plots, it is encouraging that mixing cultivars did not leave the plots more vulnerable to disease as some farmers fear. We will use these data to continue to promote this approach to farming.

As reported in previous years, we found that yields of cultivar 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.

Collaborators: