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Al's Orchid Greenhouse
204 Masons Lane S.E.
Leesburg Virginia 20175
Local to D.C., Maryland and Northern Virginia
Beautiful Orchid plants in flower
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Phalaenopsis Crown, Stem and Root Rot

websr2Here 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 rots of all kinds.  In nature most Phals grow on the sides of trees with their roots exposed to moving air and their leaves oriented in such a way that water runs off  and away from the crown.  Grown in a pot the opposite is true.  Water collects in the crotches of leaves around the crown where most rots begin.  Rots 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 overnight.  A closer look reveals necrotic, infected tissue at the base of the leaf where it connects 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.

Phals are also very susceptible to root rot.  Frequently the only symptom that the owner notices is drooping, withering or wilting leaves weeks or months after the infection has killed off the roots.   The most common reaction to a wilting plant is to add water more frequently.  In this case that is wrong.  Before determining if it is insufficient water or a root rot, you must check for live roots.  A plant without roots in a media full of rot spores can not draw up water into those wilting leaves no mater how often water is poured into the pot.  If root rot is discovered, repotting in fresh new potting media will set the plant on the path to recovery.  During the recovery period, a tad less light and air movement may preserve the remaining life in the leaf and stem tissue long enough for new roots to initiate.

Recovery is usually a long road no matter which part of the plant the rot has attacked.

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.  I do NOT recommend misting a plant.  Mist the air around the plant to increase humidity, don’t regularly spray water on the leaves.
Extended periods of cool temperature increase the chances of infection.

These tips work to remove the conditions that 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.

Cinnamon is often recommended for fungus infections as a cure or preventative.  Here’s my take on Cinnamon as a fungicide.  It is well known that cinnamon has some fungicidal properties.  However the cinnamon you buy in stores is grown for food and human consumption; not pesticide use.  The volume of the fungicidal agents in the shaker may or may not be present in sufficient quantities to help.  And of course, a fungicide will not help if the rot is caused by bacteria.  Still some people swear by it.

websr1I treated the above plant about six months prior to this writing or taking pictures.  At this point 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.  They 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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This entry was posted on Tuesday, July 7th, 2009 at 7:19 am in my Red Tag Journal where I post interesting things and pretty pictures. If it is not also found in my Online catalog and Shopping Cart., by searching the name or tag number, then it is NOT FOR SALE.

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