![]() While yield loss is rare, it has been documented in at least two situations. Phoma black stem lesion (Right) compared to a Phomopsis stem canker lesion (Left) Conversely, lesions caused by Phomopsis stem canker and Sclerotinia mid-stalk rot will degrade and weaken the pith.įigure 3. Additionally, Phoma black stem lesions will remain superficial and healthy white tissue is apparent if the lesion is shaved off. Sclerotinia mid-stalk lesions are distinctly cream to tan colored. Phoma lesions are distinctly black, while Phomopsis stem canker lesions are distinctly brown. Lesion color can be diagnostic for sunflower stem lesions. Numerous Phoma black stem lesions in a sunflower field High humidity also contributes to the disease cycle.įigure 2. Many lesions can occur on the same plant, and numerous lesions can occur in a canopy. Infected leaves (and subsequent stem lesions) are often limited to the lower half of the plant due to spores dispersed by rain splash. Phoma black stem lesions on a single stem A small (approximately 2 inches long by 1 inch wide) coal-black stem lesion forms on the stem at the base of the petiole.įigure 1. Foliar lesions are difficult to distinguish from other sunflower diseases or ailments (such as Phomopsis stem canker), and generally not considered diagnostic. Infection often begins on leaf margins, and a chlorotic and necrotic angular lesion will form and progress across the leaf, through the petiole and into the stem. ![]() Infection occurs when fungal spores are splash dispersed from residue and land on leaves during a period of free moisture. The fungus survives on infested sunflower residue. Yield loss has been documented, but is believed to be rare. While the disease occurs in the High Plains and Southern Plains states, it is less prevalent. Phoma black stem is the most commonly occurring stem disease in the US Northern Great Plains. Home » Growers » Diseases » Phoma Black Stem ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |