First report of Pantoea agglomerans causing onion leaf blight and bulb rot in Michigan.
Between June and September of 2013, sweet onions (Allium cepa) in six different counties in Michigan displayed symptoms similar to those caused by infection from Pantoea agglomerans or P. ananatis. Symptoms included leaf and stalk water-soaked or necrotic lesions. In scouted fields, disease incidence progressed throughout the season and reached an incidence of up to 80% or more in some fields. Symptomatic samples of six cultivars were collected from each county for disease identification. Based on the results of morphological observations and biochemical, molecular (rDNA sequencing) and pathogenicity tests, the causal agent was confirmed as P. agglomerans. The pathogen has been reported to infect onion in Cuba, Israel, and South Africa. In the USA, it was first reported in 2006 as a causal agent of leaf blight and bulb rot of onions in Georgia. This is thought to be the first official report of P. agglomerans-infected onion, as part of the leaf necrotic and "bulb rot complex" in Michigan.