Comprehensive Disease Survey of U.S. Sunflower: Disease Trends, Research Priorities and Unanticipated Impacts

Abstract

Between 2002 and 2015, a comprehensive survey of sunflower fields across seven Midwestern U.S. states was conducted 12 times and continues to be conducted every other year. The surveyors collected data on yield, agronomic management factors, disease, insect, weed, and bird damage. All surveyors were volunteers and came from universities (extension and research staff), USDA-ARS, and seed and chemical companies. In the 12 years the survey was conducted, data from 2,267 fields were collected. The results are presented annually at the National Sunflower Association Research Forum and are used to set sunflower research priorities. While 10 diseases are surveyed annually, we focus this article on the importance, findings, implications, and impacts of the five most important: downy mildew, Phomopsis stem canker, rust, Rhizopus head rot, and Sclerotinia head rot. This survey is unique among field crops in both scope and scale, and this manuscript discusses salient and clandestine benefits of intense and long-term disease surveys.

Registration of Oilseed Sunflower Germplasms RHA 478, RHA 479, RHA 480, and HA 481 Providing Diversity in Resistance to Necrotrophic Pathogens of Sunflower

“…In the soil, it survives as sclerotia where it can live for up to 7 yr. The pathogen causes three yield‐limiting diseases in sunflower: wilt and basal stalk rot, mid‐stalk rot, and HR (Gulya et al, 2019). The scale of the disease problem in susceptible crops led to the formation of the USDA‐led National Sclerotinia Initiative, which has invested in the development of resistant cultivars of many crops, including sunflower, as part of a research strategy to limit the effects of Sclerotinia.…”

“…Symptoms start on leaves and spread to the stalk, where tan to brown color lesions form (Talukder et al, 2014). Gulya and colleagues (2019) conducted a disease survey for US sunflower growing regions: North Dakota and Minnesota, South Dakota, Central High Plains, and Texas (TX). Mean incidence of PSC increased from 5 to 7% in Texas, 15 to 35% in the Central High Plains, 16 to 50% in South Dakota, and 25 to 56% in North Dakota and Minnesota from the first 6 yr (2002–2008) to the last 6 yr (2009–2015) of the survey.…”

Registration of Oilseed Sunflower Germplasms HA 482, RHA 483, and RHA 484 Selected for Resistance to Sclerotinia and Phomopsis Diseases

“…DeBary) and Phomopsis stem canker (caused by Diaporthe spp. Nitschke) are among the most important diseases in sunflower in North America and worldwide (Gulya et al, 2019).…”

“…Resistance to Phomopsis stem canker is a critical trait in modern sunflower germplasm, as the disease has reduced yield worldwide since the early 2000s, particularly in the United States and Canada (Gulya et al, 2019). Phomopsis was previously thought to have been caused solely by D. helianthi (Muntanola‐Cvetkovic et al, 1981), but recent research suggests that up to 10 or more different species may cause disease in sunflower, including D. gulyae (Thompson et al, 2011), the species found to be the primary cause of Phomopsis in Australia (Mathew et al, 2015).…”

“…Phomopsis has caused catastrophic yield loss worldwide. In Minnesota and North Dakota sunflower fields, for example, the mean prevalence of Phomopsis increased by 38% between 2002 and 2015, with reports of seed company nurseries and commercial fields being destroyed (Gulya et al, 2019). In Europe, yield reductions of up to 40% have been recorded (Masirevic and Gulya, 1992).…”