Question
Hi
I have recently bought my first Dendrobium and in the space of about 5-6 days one of the leaves have begun to, what looks like, dry out.
This dried out patch is about the size of a large thumb nail and is about an inch from the stem. It looks as if all the water in the cells in this area has been sucked out of them. The stem is young and the leaf is the second from the top (there are four leaves on this stem). I haven't noticed this anywhere else on the plant.
I have recently treated my Dendrobium for a fungal infection and had to remove a black spot from another leaf on a different stem but in the same pot. I'm not sure if this has any significance but I thought it would be better if i included it.
I'm living in Australia and it's almost the end of summer and my Dendrobium has just finished flowering.
I'm quite worried about this patch as it continues to grow each day and I haven't been able to find anything on the web. Any help or advice would be greatly appreciated.
- Cleo

Answer
Hi Cleo,

My first thought was that the patch could be sunburn but reading further into your note, I'm not certain.  Another possibility is an insect but usually they cause damage sporadically on the leaves rather than one spot.  It also could be a bacterial infection but those are usually watery looking rather than dry.  

My last thought is that it could be a fungus infection called anthracnose which can appear when temperatures are warm, humidity is high, plant is kept constantly moist in the presence of inadequate light intensity and air movement.  When the patch first appeared, was it reddish brown in color then slowly becoming dark brown?  If it was, this is what it could be.  This is usually not fatal but unless the infected leaf is removed and the infection allowed to become dry, fungus spores may be released onto other leaves and spread the infection.  To prevent this, remove the entire leaf and dispose of it.  In the event that some spores have been spread, spray the entire plant with a fungicide containing copper.  Not sure what is available in Australia so ask at your local garden center or nursery for a recommendation.  

Hope this helped.  

Jim Kawasaki
San Jose, Ca.