Bacterial Blight Alert

It's only the beginning of 1999 and we are already seeing evidence of Bacterial Blight of geranium popping up all over the place. This devastating disease was identified in stock material submitted to the C. Wayne Ellett Plant and Pest Diagnostic Clinic, The Ohio State University as early as November of last year. This is the earliest in the growing season this disease has been confirmed in my 13 years at Ohio State. For those of you that are not familiar with this most serious of geranium diseases, the disease is caused by the bacterium Xanthomonas campestris pv. pelargonii (Xcp). Initial symptoms of the disease may manifest themselves as small, oily looking spots on the leaves of the affected geranium. These spots may continue to enlarge and turn brown and dry until the entire leaf appears dead. In the greenhouse the symptom that is the seen in the majority of cases is leaf wilt. (Please refer to the September 1996 issue of the Ohio Floriculture On Line (on the Internet) Newsletter for pictures of the symptoms associated with this disease.)

If leaf wilt symptoms occur on any geraniums in your greenhouse the first thing to do is to check the roots. If the roots look white and healthy, the wilt may be associated with Bacterial Blight and with common root rot. Symptomatic plants should be immediately removed from the bench and isolated from the other geraniums. Suspect plants should be tested for the presence of the bacteria by a university-based or private testing lab. This is the only way that you can be confident that the affected plants are infected or not infected with Xanthomonas campestris.