|Rooney-Latham, Suzanne -|
|Miller, Jean -|
|Kosta, Kathleen -|
|Murphy-Vierra, Colleen -|
|Larson, Carrie -|
|Kandel, Hans -|
|Vaccaro, William -|
|Nowatzki, John -|
Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 5, 2012
Publication Date: December 14, 2012
Citation: Gulya Jr, T.J., Rooney-Latham, S., Miller, J.S., Kosta, K., Murphy-Vierra, C., Larson, C., Kandel, H., Vaccaro, W., Nowatzki, J.F. 2012. Sunflower diseases remain rare in California seed production fields compared to North Dakota. Plant Health Progress [online]. Available: http://www.plantmanagementnetwork.org/pub/php/research/2012/sunflower. DOI:10/1094/PHP-2012-1214-01-RS. Interpretive Summary: Sunflower seed for planting purposes is largely grown in California, where the long, dry summer is conducive for optimal seed yields with a minimum threat of plant diseases. This lessened chance of disease insures that American growers receive disease-free seed, and also makes export easier since phytosanitary restrictions are easily met. Over the last 15 years (1997 to 2011), over 7000 seed production fields were inspected in northern California, and suspected disease samples were identified at the central state diagnostic laboratory in Sacramento. The professional staff of the California Department of Food and Agriculture documented instances of only three quarantine-restricted diseases over that period of time: rust, downy mildew and Sclerotinia stalk rot, which occurred in 4.9%, 2.6%, and 0.5% of inspected fields. In contrast, sunflower fields in North Dakota, where approximately half of the U.S. crop is produced, had quarantine-level diseases in 88% of the fields, which explains why planting seed is largely grown in California. This study provides current data to substantiate that California-produced seed is largely free of diseases of quarantine concern to foreign countries, and that California's present system of field inspection and laboratory diagnosis is very thorough.
Technical Abstract: The majority of United States sunflower production is in eight Midwestern states, but hybrid planting seed is almost exclusively produced in California. Due to the lack of summer rains and furrow irrigation, California-produced seed is relatively disease free and thus it regularly meets phytosanitary restrictions imposed by many countries. For the 15-year period from 1997 to 2011, 7231 seed fields in northern California were inspected and samples processed at the state diagnostic laboratory (California Department of Food and Agriculture). Rust (Puccinia helianthi) was the most prevalent quarantine disease, found in 4.9% of fields. Stalk rot (Sclerotinia sclerotiorum) and downy mildew (Plasmopara halstedii) were the only other quarantine pathogens observed, found in 2.6% and 0.5% of the 7231 fields, respectively. Many sunflower pathogens have never been recorded in California, including Phoma macdonaldii, Phomopsis helianthi, or any virus. North Dakota, the state with the highest U.S. sunflower production, had quarantine pathogens in 88% of surveyed fields from 1995 to 2011. Phoma macdonaldii, Sclerotinia sclerotiorum, Puccinia helianthi, Phomopsis helianthi, and Verticillium dahliae were recorded in 67, 53, 45, 27 and 12%, respectively, of 1263 fields surveyed.