Michigan celery field and greenhouse yield and quality is negatively impacted by soilborne pathogens. Celery growers have observed a crown rot, wilt, and vascular discoloration called "meltdown". Symptomatic celery plants were collected from seven grower commercial grower fields across four counties and two years. Isolations showed the most common organisms observed were Fusarium solani species complex (52%) and Fusarium oxysporum species complex (45%) as identified by sequencing of the translation elongation factor-1Îł. Isolates identified as Fusarium oxysporum f. sp. apii race 2 (Foa race 2), the cause of Fusarium yellows, using diagnostic primers caused disease in a growth chamber pathogenicity assay. Foa race 2 isolates are capable of causing disease symptoms but are infrequent so "meltdown" may have additional cause(s). Pythium root rot decreases quality of greenhouse grown celery transplants. Pythium spp. isolated from symptomatic celery seedlings were characterized by virulence and fungicides tested for control of Pythium root rot. The most frequent Pythium species collected from Michigan celery were P. mastophorum (55%), P. intermedium (16%), P. sulcatum (10%), P. aff. diclinum (6%), and P. sylvaticum (5%). P. sulcatum and P. sylvaticum caused disease symptoms on celery seedlings in a greenhouse virulence assay. Phosphorous acid salts, ethaboxam, and mefenoxam controlled Pythium root rot in a greenhouse setting. Results indicate which Pythium spp. are of most concern to celery growers and identify effective chemical controls. Understanding presence and virulence of soilborne plant pathogens in Michigan celery production will be used to develop strategies to limit disease
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