Cause Curtobacterium flaccumfaciens pv. poinsettiae, a bacterium that can be spread by cutting tools, and hands, working from infected to healthy plants, splashing water, and in contaminated growing media, Infection of leaves occurs through stomates. Warm growing conditions and high-nitrogen fertility have been associated with the disease. Has become a rare problem.
Symptoms Water-soaked to brown streaks on stems can extend into petioles. Cankers also may girdle the stem. Spots and blotches may be on leaves, which fall prematurely. Woody stems may show yellowed cortex and darkened vascular tissue. If severe, stems may crack, and an amber-color bacterial ooze may develop.
Cultural control
- Scout regularly and remove and destroy infected plants.
- Avoid overhead irrigation or any practice that keeps plants wet for extended periods of time. Individual drip watering of pots can also help.
- Keep humidity as low as practical.
- Wash hands, and keep cutting tools disinfected.
Reference Pirone, P.P., and Bender, T.R. 1941. A new bacterial disease of poinsettiae. N.J. Agric. Exp. Stn. Nursery Disease Notes 14:13-16.