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Halo blight of beans
Pseudomonas syringae pv. phaseolicola
  • halo blight

Plant hosts
All Phaseolus crops are susceptible to halo blight including Phaseolus acutifolius (tepary bean), P. coccineus (runner bean), P. lunatus (lima bean), and P. vulgaris (common bean). 

Early symptoms develop on the first or second trifoliate leaves as small, water soaked spots that enlarge, and then turn red-brown and necrotic. A large lime green to yellow halo surrounds the lesion. Under humid or wet conditions, cream to silver colored bacterial slime form on the lesion surface and are spread with water from rain or irrigation. Plants can be defoliated when disease is severe. Bean pods have dark, greasy-looking spots that extend through the pod. Lesions later become sunken, dry, and reddish-brown.
Symptomatic bean and leaves
Symptomatic bean pods and leaves.
Image courtesy of Elaine Rody.

Halo blight is a seedborne disease.  Once lesions develop, bacterial cells are produced on the surface of the leaf and are easily spread with water during irrigation and rainfall.  Bacteria can also be moved with contaminated machinery or wet clothing.  The bacteria do not overwinter in the soil.

Geographic distribution
Halo blight of beans is distributed worldwide.

Applicable regulations
603-052-0385, Bean disease control area order; Malheur County
Return to plant pathogen profile list.