Christina Cowger

Current research shows that fungicide applications made to wheat in the absence of fungal disease are not profitable. However, in recent years, growers have been making fungicide applications on a calendar basis, and have periodically experienced enough yield and quality improvements to begin including these applications as a routine component of their spray program. Informal grower research indicates that a fungicide application at flowering protects test weight. This study aims to identify the optimal disease management strategy that will achieve the widest profit margin and return on investment to the grower. Specifically, the objectives of the project are to: 1) Evaluate efficacy of active ingredients and application timing on wheat yield and quality; and 2) Determine the overall economic benefit of the disease management options when weighing input costs against fungicidal treatments.

North Carolina wheat producers are faced with several production challenges. First, the ideal dates for planting wheat herald the beginning of soybean and cotton harvest. Consequently, wheat planting is often delayed until cold wet weather has set in, and wheat development suffers. There would be great benefit in being able to plant wheat before soybean harvest. Second, no-till wheat production, while highly successful in the Piedmont, has largely failed in the Coastal Plains and Tidewater. This failure is due to slower tiller development, and increased damage from wireworm and Hessian fly, compared to conventional-till wheat. It would be ideal if growers across North Carolina could successfully plant wheat no-till. Third, if Coastal Plains and Tidewater producers are unable to plant no-till, a conventional-till system for planting early would be advantageous to avoid conflicts with soybean harvest. Fourth, all small grain producers would benefit from knowing what varieties can be planted to minimize the risk of Spring freeze injury.

This project builds on Dr. Weisz's analysis that disease thresholds should be used to determine whether applying a fungicide to wheat will be economical. Of the four main fungal diseases that frequently attack North Carolina small grains and may necessitate fungicide application, Stagonospora nodorum blotch (SNB) probably causes the greatest difficulty in deciding whether a fungicide will be profitable. SNB can cause mild to moderate damage to crops of wheat and triticale in North Carolina. The disease is also known as Septoria or leaf and glume blotch. Fungicide decisions can be difficult with this disease because it is present every year in North Carolina, but epidemics vary greatly in severity from field to field and year to year. Many crop advisors are aware of SNB, yet few can reliably recognize it, let alone determine when an SNB epidemic has reached the economic threshold where applying a fungicide will be profitable. Consequently, the economic benefits associated with fungicides in disease control are not always realized.

This task order will fund a research graduate assitant who will work with small grains.

The objective of this work is to improve evaluation and selection efficiencies for resistance to Fusarium Head Blight (FHB) (Scab) and Septoria (Staganospora) Glume Blotch (SNB) in wheat by building a two-acre portable above-ground irrigation system that generates fine droplets at the Cunningham Research Center, Kinston, NC. The breeding program at NC State has been working on FHB since 1997 and the recent variety release NC-Neuse has moderate levels of resistance to the disease. But the level of resistance in NC-Neuse and other moderately resistant varieties such as Roane and Vigaro Tribute are insufficient to protect the crop in severe epidemics. During the past seven years we have been incorporating resistance to FHB from numerous US and foreign sources into our breeding populations and honing our skills working with FHB in both greenhouse and field nurseries. Conducting precise research with the FHB fungus is difficult because it requires very specific environmental conditions for infection and development. Temperature and humidity seven days prior to flowering and 14 days following flowering are critical if one is to collect reliable data that permits timely research progress. We have been using a 0.25 acre misted nursery at the Cunningham Research Center, Kinston, NC to evaluate and select among breeding lines. However our FHB breeding program has expanded to the point where we need to build a larger and more dependable mist irrigation system. We will be evaluating several thousand advanced generation lines during the 2004-05 season that are segregating for FHB resistance. Having brought the materials to this advanced generation stage we need a first-rate field nursery operation to bring these research efforts to fruition in terms of improved varieties. This irrigation system will also permit an expansion of research efforts directed at Septoria Glume Blotch (SNB). This disease occurs annually in North Carolina but with limited resources most research efforts in the past have been directed to the more ubiquitous powdery mildew and leaf rust fungi. Dr Cowger successfully demonstrated the utility of a new field inoculation technique for SNB during the 2003-04 season and wishes to expand this work to include all released varieties and advanced generation lines.