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Inoculum density of Plectosporium alismatis, a potential mycoherbicide, in relation to control of the aquatic weed Sagittaria montevidensis

Densidade de inóculo de Plectosporium alismatis, um potencial micoherbicida, em relação ao controle de Sagittaria montevidensis

Sagitaria montevidensis (arrowhead) is one of the worst weeds of irrigated rice. Control of this weed by means of chemical herbicides has become increasingly difficult on account of herbicide resistance in populations of S. montevidensis. Mycoherbicides are recognized as potential alternative tools against S. montevidensis. In Australia, the fungus Plectosporium alismatis was reported as a possible mycoherbicide for Damansonium minus and other alismataceous weeds, but Australian isolates of the pathogen did not infect S. montevidensis. In contrast, Brazilian isolates of P. alismatis obtained from S. montevidensis have shown promise in controlling the weed. The present study investigated effects of different inoculum densities of a selected strain of P. alismatis on S. montevidensis. Respective densities of 2 x 10(6) and 2 x 10(7) conidia.mL-1 caused an average of 86 and 93 % leaf blight followed by growth cessation and death of the plants. It was concluded that a density of 2 x 10(6) conidia.mL-1 was sufficient to control S. montevidensis and that this density should be adopted as standard in future experiments.

Rhynchosporium alismatis; arrowhead; biological control; mycoherbicide


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