Guignardia bidwellii (grape), Xanthomonas campestris (brassicas)
Serious disease affecting grapes and cabbage family crops. Different pathogens cause black rot in different crops. Can destroy entire grape crop.
Grapes: tan spots with dark borders on leaves, shriveled black 'mummified' fruit. Brassicas: V-shaped yellow lesions from leaf margins, blackened veins.
Fungal (grapes) or bacterial (brassicas) pathogens. Overwinter in infected plant debris and mummified fruit.
Rain splash, wind, contaminated tools. Spores released during wet weather.
Warm, wet weather (60-90°F). Extended leaf wetness. Poor sanitation of previous crop debris.
Remove all mummified fruit and infected canes. Prune for good air circulation. Plant resistant varieties. Rotate brassica crops 2-3 years.