FUSARIUM BASAL PLATE ROT (FUSARIUM OXYSPORUM F. SP. CEPAE) AND PINK ROOT [PHOMA TERRESTRIS (SYN. PYRENOCHAETA TERRESTRIS)] RESEARCH IN WESTERN COLORADO

Curtis E. Swift 1 and A. Wayne Cooley 2

1 Area Extension Agent (Horticulture), 2 Area Director and Extension Agent (Soil & Crop Science), Colorado State Univ. Coop. Ext., 2775 US Hwy 50, Grand Junction, CO 81503

Fusarium basal rot caused by Fusarium oxysporum Schlechtend.:Fr. F. sp. cepae (H.N.Hans.) W.C. Snyder and H. N. Hans and pink root caused by Phoma terrestris E. M. Hans. [syn. Pyrenochaeta terrestris (E. M. Hans. ) Gorenz, J. C. Walker & R. H. Larson] are serious problems in many onion fields in Western Colorado. Movement of propagules in irrigation water combined with their longevity in soil precludes the use of rotation as a control option.

Research to determine the susceptibility of various onion cultivars to these pathogens and their related yield has been conducted in Western Colorado since 2001 to assist growers in their selection of onion cultivars. Trials were placed in commercial onion fields in Delta and Montrose Counties with seventy-three cultivars examined during this four year period. Some cultivars experienced up to 51% loss during the growing season due to Fusarium basal rot and up to 42% infection by pink root. Data were statistically analyzed and reports disseminated to growers via ListServes, at grower workshops and through web pages.

The results of this research are posted on the Internet at http://westernslopevegetables.org .

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