An Example of Stem Rot or Crown Rot on a Phalaenopsis Seedling

Here is an example of a Phal seedling in a 2.5 inch pot recuperating from a bout of stem rot or crown rot.  Phals are highly susceptible to Stem rots and Crown rots.  They spread quickly and have usually killed or damaged the important  growing tip in the crown before they are discovered.   The most obvious symptom is leaves that turn yellow and blacken over night.  A closer look reveals necrotic, infected tissue at the base of the leaf where it attaches to the crown or stem of the plant.  If not stopped the pathogen will turn a healthy rapidly growing plant into mere compost in a matter of days. Notice that the problem is named after the location of the symptom and does not identify the causative agent.  The word 'Rot' implies a fungus to many people.  However, it could be any one of many bacteria or fungi species.  While fungus are probably responsible for most of the crown and stem rot symptoms you will encounter, rapidly spreading areas of mushy water filled leaf or root tissue are a symptom of bacterial infection. Here are some tips to PREVENT these problems: Use fans to keep air moving around the plants 24/7. Irrigate with room temperature water.  Don't water with cold tap water.  Make sure the crown and crotch areas of the leaves are dry before night fall when temperatures are normally declining. Extended periods of cool temperature increase the chances of infection. These tips work to remove the conditions that fungus spores need to have in place before they can inoculate healthy plant tissue; 1) still air 2) water 3) cool and/or declining temperatures. Here is what I did to stop the progress of the rot in the plant above. Initially the rot destroyed a dime sized area in the crotch of a lower leaf on the side of the stem.  The lower leaf yellowed overnight which alerted me something was wrong.  Examination revealed a darkened area of infection eating into the side of the stem. I choose to kill the causative agent with an application of Physan 20 which works to kill most fungus and bacterial pathogens on contact.  I drenched the plant with a solution made by following the label directions, covering all surface areas and soaking the potting media.  I also sprayed the area, the pots and the plants all around the location where the infected plant was found in order to kill any other bacteria or fungus that might have already spread to nearby fresh tissue.  Then I left it alone. That was six months ago from the time of this writing. At this point, as the two pictures above illustrate,  the seedling is well on it's way to developing a new crown from uninfected tissue below the destroyed older crown.  Live, uninfected plant tissue is very capable of 'compartmentalizing' when damage or disease occurs.  The cells in this plant's tissue immediately responded to the invasion of the pathogen by separating from the damaged cells by walling them off and isolating them and then turned their effort to the production of new plant parts.  The Physan 20 insured that there were NO rapidly growing pathogens left alive that could spread to these cells. Soon after the infection it became apparent that the damage to the meristematic growing tip was severe.  All growth from this part of the plant stopped a long time ago.  It also became apparent that the plant had been old enough to have produced at least one dormant growing tip in the stem tissue under the damaged area.  Leaves above the damaged crown have been slowly dying off as they translocate the usable nutrients in their cells downward to the new growing tip and roots, thus allowing for rapid development of the new crown.   Notice that the roots have continued to grow vigorously from the old crown and have actually pushed the new crown as well as the small of amount of moss in the pot up and out. This seedling may bloom in as little as 16 to 24 months on the new growth.  The last part of the old growth, the roots and old stem will eventually die off too, but only after the new crown has established itself and grown its own roots.

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