Propagated cuttings susceptible to bacterial soft rot pathogens

The environmental conditions found in propagation areas, including warm temperatures, high relative humidity and leaf wetness, can create the ideal environment for bacterial soft rot pathogens. Plant pathologist Jan Byrne at Mich. St. Univ. Diagnostic Services said one of the most common problems she is seeing on plant samples submitted to the university’s diagnostic lab is bacterial soft rot on propagated cuttings.
Several bacterial pathogens, including Erwinia, Pseudomonas and Xanthomonas, cause soft rot symptoms. Byrne said symptoms include water-soaking, collapsing of tissue and in general a slimy rot. In some cases, the main stem is primarily affected, in other cases the disease quickly progresses on the foliage. The end result is complete collapse of unrooted cuttings and young plugs. Young, tender tissue is particularly susceptible.
Byrne recommends careful scouting of propagating plants. Plants exhibiting soft rot symptoms should be quickly removed and destroyed. Byrne said chemical treatments may help limit disease spread but will not cure plants that are showing symptoms. Equipment used in propagation should be regularly disinfested.