Spider Mites or Mold? - Orchid Board

scy · #1 06-30-2011, 10:25 AM

I just bought a dendrobium. I unpotted to check the roots and potted it back up after noticing that the roots were in good condition. I used leca and added a mosquito dunk (still have a few fungus gnats left). The next day I noticed some white fuzz or webbing on the top layer of the bark mix and on the bottom of the pot. I rinsed it thoroughly under the sink and haven't seen any more webbing on the top layer of the medium. However, the bottom of the pot keeps appearing. I thought it might be spider mites, so I sprayed the bottom with malathion but it came back the next day. Is this fuzzy mold or spider mites?

I have a cymbidium infested in mites (no webbing) and scale and plan on doing a systemic dunk later today. If these are spider mites on the dendrobium, can I dunk the entire plant in the systemic or best to do the medium and then spray the leaves and cane individually?

If it's mold, should I just soak the whole thing in physan 20 solution (1 tsp per gallon dilution)?

Thanks for your help!

Vanda lover · #2 06-30-2011, 10:35 AM

It sounds like the same mold that I have on my Masd. pot. It is kept moist and cool, and a whitish web like mold has grown on the outside of the pot. I haven't done anything to get rid of it yet, other than wipe it off, but it seems harmless. I've never used physan and I'm not familiar with it, but a weak hydrogen peroxide solution might also work, and is harmless.

scy · #3 06-30-2011, 10:39 AM

I just realized I forgot to attach the photos.

Vanda lover · #4 06-30-2011, 11:40 AM

That is the same kind that was on my masd. pot. The pot dried out slightly and the mold disapeared. I would just wipe the pot with something to sterlize the outside, and let your medium dry out a little. That seems to be all it needed to get rid of mine. It seems pretty hamless.

scy · #5 06-30-2011, 01:25 PM

Thanks for your quick reply! I just wound up unpotting to clean it up. Had to reposition and stake it better since the whole thing was falling over. I also cleaned the leca and hope that this works. I have my other orchids set up the same way but it only affected this one.

scy · #6 07-01-2011, 08:55 AM

I just noticed this morning that it's on the top layer of the bark again. Is this a sign that my bark needs to be changed?

Vanda lover · #7 07-01-2011, 10:29 AM

It may be that you aren't letting it dry out enough between waterings. Dendrobium don't like it too moist. If the bark appears to be braking down, it could be time to change it.

tucker85 · #8 07-01-2011, 10:39 AM

You mentioned Physan 20. If you already have some you can treat the plant and the humidity tray with it. It's a mild fungicide/bacteriacide. I use it at 1 tablespoon per gallon. In fact I would probably keep some Physan in the humidity tray all the time. Fill a container with water and then add the Physan. If you add the water to the physan it creates a lot of foam. Good luck.

scy · #9 07-01-2011, 10:50 AM

Quote:

Originally Posted by Vanda lover

It may be that you aren't letting it dry out enough between waterings. Dendrobium don't like it too moist. If the bark appears to be braking down, it could be time to change it.

It happens a day after watering. When I first brought it home, it was bone dry from shipping so I soaked it for a few minutes to let it take in water. The very next day, the mold was on the surface and underneath the pot. I cleaned it off and it was there again the next day. I let it go bone dry and it was still there.

How can I avoid mold if it's showing up before it even has a chance to dry out after watering?

I'm not sure how to tell if the bark is braking down. With my other orchids, I could only tell when it smelled bad and I unpotted to find chunks of white and green mold. When I put it back into the pot, I didn't see any bark that broke into grain when I touched it.

scy · #10 07-01-2011, 10:51 AM

Quote:

Originally Posted by tucker85

You mentioned Physan 20. If you already have some you can treat the plant and the humidity tray with it. It's a mild fungicide/bacteriacide. I use it at 1 tablespoon per gallon. In fact I would probably keep some Physan in the humidity tray all the time. Fill a container with water and then add the Phyan. If add the water to the physan it creates a lot of foam. Good luck.

That's a wonderful idea. I'll try it!