The widespread outbreak of Alternaria leaf blight in sunflower has emphasised the extent to which oilseed research in South Africa has been neglected, according to Chris Schoonwinkel, a sunflower producer near Wesselsbron in the Free State.
Foliar diseases in sunflower are caused by various pathogens, including Alternaria helianthi, Puccinia helianthi and Septoria helianthi. Alternaria survives between sunflower crops in infested crop debris, on weed hosts and on seed. The disease starts when spores land on leaves or stems, germinate in the presence of moisture, and directly penetrate and infect the leaves.
SUNFLOWER LOSSES
Alternaria leaf blight appears as circular, dark brown to black lesions, with concentric rings ranging from 0,2mm to 0,5mm in diameter. Lesions eventually enlarge in size and coalesce, causing blighting of the leaves. Some lesions can be identified by distinct yellow halos, particularly on young plants. If the disease is severe, plants may defoliate prematurely and die.
Esta historia es de la edición Farmer's Weekly 27 April 2018 de Farmer's Weekly.
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