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ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Sunflower and Plant Biology Research » Research » Publications at this Location » Publication #138993
Title: FIRST REPORT OF CHARCOAL ROT (MACROPHOMINA PHASEOLINA) ON SUNFLOWER IN NORTH AND SOUTH DAKOTA

Author
item Gulya Jr, Thomas
item Krupinsky, Joseph
item Charlet, Laurence

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2002
Publication Date: 8/1/2002
Citation: Gulya Jr, T.J., Krupinsky, J.M., Draper, M., Charlet, L.D. 2002. First report of charcoal rot (Macrophomina phaseolina) on sunflower in North and South Dakota. Plant Disease. 86(8):923. 2002.

Interpretive Summary: Most sunflower diseases occur nationwide in the United States. A few diseases, because they are more prevalent in specific weather conditions, are frequent in one area and totally absent in other areas. Charcoal rot is a disease that attacks corn, soybean and sunflowers, and is most often seen during hot, dry summers on plants under drought stress. It had not been observed on any crop in North Dakota. In 1998, which was a hot, dry summer in south central ND and adjacent SD, the disease was observed for the first time, but was not found in areas of ND or SD where rainfall was adequate, nor has it been observed in subsequent years. Thus the disease is not considered a threat to sunflower production under current weather patterns, but could be of consequence in areas where drought is a complicating factor.

Technical Abstract: In September, 1998 symptoms suggestive of charcoal rot were observed on oilseed sunflower plants in western North Dakota (ND) and western South Dakota (SD). Symptoms, first observed on plants approaching physiological maturity, consisted of silver-gray lesions girdling the stem at the soil line, premature plant death, and reduced head diameter. The pith in the lower stem was either completely absent or was compressed into horizontal layers. Black, spherical microsclerotia were observed in the pith of the lower stem, just underneath the epidermis, and on the exterior of the tap root. Confirmation of Macrophomina phaseolina (Tossi) Goid. as the causal agent was based on the size of the microsclerotia, both from infected sunflower and in pure culture, measuring 80 to 90 in diameter (1). The only other sunflower pathogen forming microsclerotia is Verticillium dahliae Kleb., whose microsclerotia are irregular in shape and are 15-50 in diameter. Some prematurely dead sunflower plants lacked typical charcoal rot stem lesions, but did contain Macrophomina microsclerotia. These atypical plants were all colonized by the sunflower stem weevil (Cylindrocoprutus adspersus) and the black sunflower stem weevil (Apion occidentale). This is in agreement with observations in Texas where Macrophomia-infected sunflower plants parasitized by stem-feeding insects often displayed atypical charcoal rot symptoms (2). Charcoal rot incidence in 1998 in western ND was 25%, in comparison to 0% in eastern ND. Charcoal rot was not observed in 1999, the fourth wettest growing season on record, but was observed again in 2000 and 2001. The recent increase in sunflower production in western ND and SD, areas typically hotter and drier than the eastern portions of both states, and the potential involvement of stem weevils as vectors of Macrophomina (3), may lead to an increased incidence of charcoal rot in sunflower.