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Advancing Sustainable Disease Management on Field Corn in the U.S. Corn Belt

Esker, Paul
University of Wisconsin - Madison
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This project aims to increase sustainability of U.S. corn growers by demonstrating that IPM-based disease management is both cost-effective and environmentally sound for corn production. By focusing on the development and use of disease thresholds for foliar fungicide timing, the development of an area-wide approach to standardizing disease management recommendations, and the development of a regional corn fungicide resistance monitoring program, this project directly matches the goals of RAMP, as it incorporates all four PAM components: Prevention, Avoidance, Monitoring, and Suppression.

The end-result of this project will be an IPM-decision support system that has broad applicability across other field and small grain crops, especially those that historically have relied on chemical tactics for disease management. Thus, to improve corn disease management through IPM stewardship, we propose the following objectives:

  1. To develop economical foliar fungicide spray thresholds for foliar diseases of corn based on (i) spray thresholds developed using yield loss models based on coordinated field trials and (ii) field validated data from coordinated on-farm foliar fungicide trials.
  2. To determine the risk of fungicide resistance through the development of a regional resistance monitoring program in corn.
  3. To quantify the "perceived risk and need" of foliar fungicides by corn growers and Certified Crop Advisors (CCAs) through a two-stage survey of and focus group discussion with these respective groups.
We estimate that this project will reach over 10,000 or more agribusiness personnel in the U.S. Corn Belt either through new and updated corn management information or through hands-on training of field diagnostics for corn diseases and the impact of foliar fungicides on production. The research we have proposed will develop standardized screening methods for corn diseases throughout the Corn Belt, contributing to our understanding of when a fungicide application is necessary and profitable, and increase our awareness of changes in the sensitivity of E. turcicum.

The survey in Objective 3 will enable us to directly measure the impact of our Outreach and educational programs regarding the use of IPM for corn disease management. This will also provide a mechanism to quantify the economic impact of our Outreach efforts.

While Dr. Esker has a background in Plant Pathology and Statistics, our use of the UW-Survey Center will guarantee that important considerations including survey layout, anonymity of respondents, incentive for completing the survey, and the mailed reminders to complete surveys are followed.

The overall outcomes of our research are three-fold: first, disease management, particularly fungicide application recommendations, will be more updated from recent, uniform data, second, if fungicide resistance does occur, we will be able to respond in a timely manner, and third, we will greatly improve our outreach efforts with our stakeholders.

More information
Non-Technical Summary: There have been dramatic changes in corn production over the past 10 to 15 years. More specifically, in the past two years, the advent of the bioeconomy and the dramatic increase in foliar fungicide use has shifted direction away from the sound use of IPM tactics for corn disease management. Since 2006, the harvested acres of corn have increased by 10-20%, in part due to increased emphasis on biofuels and higher corn commodity prices. These shifts in production have a direct effect on the risk of corn diseases (increased threat), and consequently, impact the effectiveness of currently recommended IPM practices. There have also been dramatic shifts in foliar fungicide applications, for example, foliar fungicides were applied to approximately 10 million corn acres in 2007 at a cost of $225-250 million (approximately $23-24 per acre), mostly in the absence of an integrated pest management framework. The estimated percentage of acres sprayed in 2008 was even higher. In order to effectively improve on the current IPM approaches for managing corn diseases, we need improved understanding of the perceived risk and need for foliar fungicides by corn growers, a thorough evaluation of if and how IPM is being practiced on the farm, as well as what tools and information are lacking for broader application of IPM principles. Additionally, shifts in three core and critical components of corn production over the past decade: planting dates, corn hybrids, and new fungicide active ingredients require new information for sound use of IPM. When combined with reduced or no-till cropping systems, a production practice in effect since the early 1980's, these combination of factors can increase (and manage) the risk of a corn disease epidemic. Our project takes a multi-state approach to specifically examine the effect of foliar fungicides, the risk of fungicide resistance, and stakeholder perceptions for using IPM methods to improve disease management recommendations for corn. We directly involve our stakeholders in all three objectives. The four states that are a part of this proposal (Illinois, Iowa, Ohio, and Wisconsin) accounted for 40% of the corn harvested in 2008. Furthermore, these four states provide a diverse set of environments to examine the variability in corn response to different disease management tactics. This maximizes our ability to develop yield loss models that are necessary to quantify disease thresholds for use of foliar fungicides. Critical for our outreach efforts is that we will specifically target CCA's and growers about their "perceived risk and need" of foliar fungicides and the use of IPM for corn disease management. Our goal with this project is to increase sustainability of corn production by developing updated and new recommendations for stakeholders to make economically sound corn disease management/foliar fungicide decisions against foliar and stalk rot pathogens.

Approach: Objective 1. Field experiments will be conducted with the specific objectives of investigating: (1) the effects of fungicide application timing on foliar disease and stalk rot development and yield in hybrid corn, (2) the association between foliar disease intensity and stalk quality, and (3) the additive and/or multiplicative effects of foliar corn diseases and stalk rot on yield in hybrids with different levels of resistance to foliar diseases under different environmental conditions. Plots will be inoculated with different combinations of Cercospora zeae-maydis and Exserohilum turcicum. Additionally a single application of a strobilurin fungicide at its current recommended application rate either at anthesis, at the blister/milk growth stage, or based on foliar disease severity threshold will be made. Threshold applications will be when severity on the third leaf below the ear reaches 5% on 50% of the plants. Disease severity, stalk rind strength and rot, and yield will be collected from plots. Based on results from these experiments, on-farm replicated strip trials will be conducted to test, validate, and refine the best decision thresholds. A total of 8 on-farm trials will be established per cooperating state using commercial equipment (thereby mimicking a commercial production system). Objective 2. A resistance monitoring program will be developed and involve two phases: i) establishing a baseline sensitivity level of E. turcicum to QoI fungicides; and ii) monitoring for a shift in sensitivity of E. turcicum isolates collected from QoI fungicide applied areas. For the first phase, isolates of E. turcicum that have never been exposed to QoI fungicides will be obtained from historical collections and fields that have never received a QoI fungicide application. For the second phase, all PIs will collect E. turcicum isolates from corn fields that have been applied with a QoI fungicide. Isolates will be collected from three different types of areas: i) hybrid corn seed production fields; ii) corn foliar fungicide research plots; and iii) commercial corn fields that have been sprayed with a QoI fungicideThe sensitivity of each isolate to the QoI fungicides will be established by determining the EC50 levels using the spore germination assay. Fungicide sensitivity levels (EC50s) of collected isolates will be compared to the baseline sensitivity level each year. By making these comparisons, any shifts in sensitivity will be detected. Objective 3. To understand stakeholder perceptions regarding the implementation of IPM principles for corn disease management, we will target two of our key stakeholder groups, Certified Crop Advisors (CCAs) and corn growers using surveys. Goals for this objective are to estimate the "current knowledge" for use of IPM and foliar fungicides for corn disease management, and to integrate field research data from Objectives 1 and 2 with this third objective to obtain an economic assessment of IPM for corn disease management. We will work with the University of Wisconsin Survey Center to conduct surveys in year one and year four of this project for this objective.

Funding Source
Nat'l. Inst. of Food and Agriculture
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Chemical Contaminants
Bacterial Pathogens