Fungus/Heat Stress on Masdevallia Herradurae? - Orchid Board

RaN · #1 09-15-2014, 01:00 AM

Howzit. Sunken yellowish spots have been appearing on the undersides of this Masdevallia Herradurae and also on a Dracula Lotax that was next to it. There are also darker brown to black spots as well.
I have had the plants for 3 weeks and they came to me a little weathered but still very healthy. These two plants are grown outside under a covered walkway, facing a westward direction. They do receive some direct sunlight after 2-3 pm but only for a couple of hours before the light is filtered through some trees. Temps here range from very low 80s/high 70s in the day and may drop down to mid 50s/low 60s at night. Some nights are cooler depending on sun or rain during the day. It does rain often here. I live at 2700 ft level or so. Both plants are putting out new growth and possible inflorescence. The pics show the sunken areas and spotting on the Masd. in red circles and new growth in green. Could these spots be fungal? Heat stress? Any help will be appreciated.

WhiteRabbit · #2 09-15-2014, 09:09 PM

Matorchid · #3 09-19-2014, 09:01 PM

Mines not a Madevallia, but I have had pretty much the same thing.
Mine was misting a little late in day on those cooler days and cold water coupled with high temps, with weakened root system made some of my plants have some brown rot.
Maybe others can narrow it down for you.
Cut away effected area with new blade, hydrogen peroxide cut areas then dab cinnamon on cuts, and questionable areas, then I just stopped misting on the cooler days and on warmer days made sure water was tepid around 80 or so. Then I decided to change some of the media on certain plants. Seems to have worked. Things returning back to normal. That was my experience and I think their a lot of this going around now with the change of seasons.
The yellowish spot will become brownish of not resolved very soon

AnonYMouse · #4 09-19-2014, 09:24 PM

I gave up growing Masdies because it's too warm here.

I would suggest potting into clay pots. Even a pot-in-pot set up (Ray has info on this somewhere on his site). Clay, through evaporation, will cool the root zone somewhat better than plastic.

Good luck!

Edit to add: Doesn't look bad. 80° should be the upper limit, don't let it stay at the temp for long. Wipe the leaves with rubbing alcohol and make sure there is good air circulation. The leaves should flutter a bit.

RaN · #5 09-20-2014, 12:17 AM

Mahalo for the replies! Matorchid I think you are right. I believe I was misting too much. I forgot to mention in the original post that I had been spraying hydrogen peroxide also. I think that may have compounded the issue since it turns to water pretty quickly and just leaves more unnecessary wetness.
Well I sprayed it down with Listerine, cut the worse leaves off, cut some of the diseased portions of other leaves and applied cinnamon. I know it is more than likely time to repot, but those are buds at the bottom. They are now all over the bottom of the plant, so I want to wait till I get to see some blooms before I repot. The dracula that I had next to it I divided and repotted. So far so good, we'll see...

AnonyMouse I bought these from a grower who lives about a thousand foot level lower than I and has warmer average temps. He has many Masdevallia and Dracula growing outdoors. This past month has been really warm though. I think temps will be ok, once I combat the fungal/bacterial infection.