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Poster: Biology & Disease Mgmt: Chemical Control


Fungicide resistance in populations of Fusarium proliferatum causing bulb rot of onion in the Pacific Northwest.
K. Fairchild (1), S. Windes (1), A. Malek (1), J. Woodhall (2), P. Wharton (1) (1) University of Idaho, U.S.A.; (2) University of Idaho, U.S.A.

Fusarium bulb rot, caused by the fungus Fusarium proliferatum, is an emerging disease on onion in Idaho. This bulb rot occurs in storage and shows symptoms similar to neck rot. Symptoms usually start at the neck and progress down along the fleshy scales, but the basal plate is not affected. Infected scales become translucent yellow and water-soaked, later turning tan-brown and soft. Frequently, the rot appears to progress down from the neck along a single fleshy scale in the bulb. In most cases the infected bulbs do not show any pronounced external symptoms or signs of infection. Currently, there are no control measures known for this disease as the mode of infection and conditions required for disease development are poorly understood. Fungicide sensitivity testing was done on a range of fungicides which have shown potential for the control of F. proliferatum using spiral plate dilution gradients. Results showed that there was a range of sensitivities in the populations of F. proliferatum to the fungicides tested. A knowledge of fungicides showing effective control of this pathogen in vitro is important in the development of effective management strategies to control this disease.