powdery mildew

[tillystuff]

Hello all, need some advice from all the folks that may have had similar issues with this problem. We started to notice the powdery looking spots about a month ago and really didn't know what it was. Now it has become a much bigger problem. We are going to seperate the affected plants from the rest today and clean them with a solution fo Physan 20. We have already began a regular spraying of all the other plants to ward off further contamination. Does anyone have a better cure for this? This is a first for us in all of our years of growing cats and we're not quit sure if this is the best solution. I will post some pics later today of the infected plants so folks can see what this Powdery Mildew looks like...it aint pretty!!!

[kmarch]

I've never had much of a problem with it on my plants but have had problems with it on some of the windowsills. It goes away in summer and comes back in winter when it is cool and humid. It may be as simple as increasing air circulation/lowering humidity, but then again I don't know your conditions. You may already be doing well in that area. I have good success with spraying Physan on plants for leaf fungus, etc. It just might do the trick.

[Cynthia, Prescott, AZ]

I am beginning to think that everyone that grows orchids should bite the bullet and buy some Phyton 27. It is a systemic bacteriocide/fungicide unlike Physan 20. I have had a major problem with a form of wilt that I have finally realized is a major killer in my greenhouse. It isn't until plants are dropping like flys everywhere that you finally come to the conclusion it isn't your mix, your culture, chance, and so on. The real eye openner was when a half dozen African violets located separately started to melt. I am spraying these plants every day with the max concentration of Phyton 27, and may still not be able to save them as I didn't spray often enough in the beginning. I know the company that makes Phyton 27 sells cases of 2oz bottles, so some where out there on the internet, one should be able to find the 2oz bottles for a little over $20. My next purchase coming up soon will be the quart size. I am using a 1/2 teaspoon to a quart for the max concentration, and am spraying anything suspecious every few days. No damage so far to the plants.

Watch out for Physan 20. I once caused a lot of strange results by watering my GH with water mixed with a little more than the recommended concentration of Physan 20. Didn't kill anything, but many plants show a white section in their leaves where they were in growth at the time of watering. One strange case of excess growth occured in a Laelia fidelensis, where the growing leaves got about 50 to 100% longer than normal.

[tillystuff]

Hello all, the pics below are what we suspect as being "Powdery Mildew" that has gotten hold on several of our catt's. If anyone has seen this and believes it is something other than "Powdery Mildew" please identify and suggest a solution. After looking on the internet for some resolution to this we saw some pics of mealy bugs. This could be them as well...don't really know as we have never had a mealy bug problem either.

[tillystuff]

Just for fun I thought I'd show you what we use for insect control. you can't get it any cheaper than this. It really works on some of them...not all!

[kmarch]

Dear tillystuff,

The pics you've posted are not of mildew. It is bosduval (sp?) scale. This kind of scale loves Cattleya types and are a bugger (no pun intended) to get rid of. I have never been able toeradicate them completely, only more or less ocntrol them. I have found systemic insecticides to be the most effective against them. They ingest a systemic insecticide via the plants sap and are killed that way. Topical insecticides are much less effective. This kind of scale loves heat. They show up on my Cattleyas (and to a much lesser extent my Cymbidiums) in summer and I spray and spray and spray, then in winter, they completely vanish only to reappear again the next summer. They like to colonize around the rhizome of the plant in a protected area like inder the potting mix or beneath a dead bract. I recommend a thorough cleaning of the plant, removing all dead bracts, unpotting the plant and removing all visible scale form the rhizome and roots , also thoroughly clean the plant itself, removing all visible scale (use a soft toothbrush to get in those tight areas like in the second pic. Repot and begin treating aggressively, preferably with a systemic. Keep this plant away form your other plants and check frequently (as in every few days) and carefully for any signs of return removign all signs of scale if you see any more. I don't want to sound like an alarmist, this plant may very well survive, but don't mess around with these guys.

Good luck!

[Cynthia, Prescott, AZ]

Scale is a killer of Catts, and you have a very advanced case. Bayer Advance Rose & Flower ready mix is a good systemic, but use it several times over a few weeks, and again occasionally. Some other Bayer Advance products have the imadacloprid of the Rose and Flower, such as the Shrub formula, but you will need to figure out how much to use to get the same concentration as the Rose and Flower (will check my usage when I get out to the GH today, as I have it marked on the bottle). Also, for a large collection in a greenhouse, the Lawn formula, again imidacloprid, which comes with a hose end sprayer, is good. I just used it on my entire highly mixed collection, and only had a few flowers fold early.

If the imidacloprid works for you, I wound not go the repot way, as you may do damage to the roots out of season. Give the Bayer Advanced Rose & Flower a try first. My experience is that repeated use of a good systemic will eventually completely rid you of the scale, unless you are growing outdoors where reinfection can occur from the neighborhood.

[tillystuff]

Hello all! Thanks so much for the great info.

This is what a forum is all about. The knowledge base of all the great folks is not to match any single web site.

We just got back from Lowes with the Bayer Advance Rose & Flower ready mix...I sure hope this works. We seem to have a nasty infestation of this scale and I'm afraid we're going to lose some plants anyway.

This is very good information for all to take in as it can do some serious damage real quick. Hopefully the pics I posted earlier will help others to identify this problem. Doing a lot of research on this...I didn't find ant real good pics that really gave me a comparison point.

Thanks again and I'll keep you posted on what the results are as I will hopefully see an improvement.

[Cynthia, Prescott, AZ]

If you spray pretty heavily, and some goes into the pot, that is good to give the plant a little systemic at the roots.

[kmarch]

Cynthia,

It's a good point you make about not repotting. If the systemics work good then there would be no need to repot and you're right to point out it could further stress the plants. Next tine I have an outbreak I will put off repotting until after I see how it goes with the systemic.

Cheers!