Bacterial blight on geraniums, again

Bacterial blight on geraniums, caused by Xanthomonas hortorum pv. pelargonii, is back this growing season. In this Alert, e-gro will discuss the symptoms of the disease and management options.

This year things have changed and we have observed the disease in multiple locations across the northeastern U.S. Therefore, we will review important facts about this disease to help growers identify symptoms and prevent spreading the disease if it enters into the greenhouse.

The “good thing” about this pathogen is that it “only” infects geraniums—unlike other bacteria, like Xanthomonas campestris, which infects a broad range of crops. Bacterial blight can infect zonal geraniums (Pelargonium x hortorum), ivy geraniums (Pelargonium peltatum), Regal or Martha Washington geraniums (Pelargonium domesticum), and cranesbill geranium (Geranium sanguineum).

The symptoms of the disease include: Small, water-soaked spots on the underside of the leaves, followed by wilting and death of the affected leaf; yellow to tan v-shaped lesions wedged between the veins of the leaves; the petiole might remain turgid, while the leaves wilt down. Some describe this symptom as “umbrellalike appearance.” The affected leaves may drop off immediately or may hang onto the plant for a week or more.. Ivy and scented geraniums do not display the distinctive symptoms described above, so keep them separate and test any incoming lots.

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