Definition of halo blight
1
or less commonly
halo spot
: a blight of beans and occasionally other legumes that is caused by a bacterium (Pseudomonas phaseolicola) and typically produces on the leaves, stems, and pods round water-soaked lesions surrounded by a yellowish zonation, the lesions finally turning brick red
2
: blight affecting the leaves of oats and other grasses caused by a bacterium (Pseudomonas coronafaciens) characterized by oval water-soaked lesions turning gray to brownish and surrounded by a pale zonation
