Subdue maxx (fungicide)
 

Well, my friend ponied up close to $300 for a quart of this, and gave me a couple of ounces. I have downloaded a copy of the label, and the usage rate is about 15 drops per gallon (or about 5 drops for my little pressure sprayer).
Has anyone used this on orchids? Specifically I want to treat Guignardia Leaf Spot caused by Guignardia species on vandaceous orchids.
Most of us in the deep south, especially along the Gulf and Florida coasts, are familiar with this apparently airborne fungus that has our foliage resembling the texture and color of an emery board after awhile...every time a hurricane blows through, this fungus seems to come with it.
So, my questions: did you use a buffer/spreader to adjust pH? I had planned to spray the affected foliage only, and also saturate the roots, since I believe this is at least slightly systemic.
Any tips very gratefully solicited. Or any thoughts.
Regards - Nancy, queen of the unsightly fungus

Sorry Nancy, I can't help.

Just giving you a :bump:

Hi Nancy -

Just be sure Subdue is the fungicide for your problem. I bought it for Pythium, a fungus that causes root rot. I discovered that Cleary's 3336 doesn't cover that fungus (I had my plant tested at the state agricultural extension). A cheaper alternative and broader spectrum fungicide is Banrot.

Generic of Subdue
 

I see that Mefenoxam, the generic of Subdue Max, is being sold.

Mefenoxam 2 AQ Fungicide | Agricultural Products

Thanks David - still pretty pricey @ $130, but less than half the price of the name brand.
Wish these things came in smaller containers; though our society has chipped in so we each get a little bit of something costly. When you only use 1ml/liter, an ounce goes a very long way!
RE: the SubdueMaxx - my most recent 2 years of foliage are unaffected, so this (alternating with Cleary's) is a good control for this fungus.
Cheers - Nancy, demoted to fungus princess

Subdue Maxx is not the agent of choice for Guignardia Leaf Spot. Cleary 3336 is listed as an appropriate treatment as well as Copper Based Fungicides, Captan 50W, Zyban, Exotherm Termil (reading off my table :D)

Subdue Maxx is about the only thing that will kill Pythium/Phytophthora. I would "save" the gift from your rich friend and use the Cleary 3336 ;)

Thiophanate methyl (Cleary's 3336, Domain, Fungo) and Mancozeb (Manzate or Dithane M45.) is a proven and recommended combination of systemic fungicides to control leaf spotting. I have had very good results using this on "Thai Crud". There is no cure but this will knock it down to where it is manageable. For new lesions, I paint over them with clear nail polish to keep them from releasing new spores. Good Luck !

You can get Banrot pretty darn cheap at
Banrot Systemic Fungicide 8 oz. - Green Barn Orchid Supplies

Subdue Maxx is a GREAT fungicide and $$$, but you use about 5-7 DROPS in a gallon as I recall. So it goes a long way. But, like the other posts it isn't for your problem. When you use it do be accurate as it can sometimes cause crippling in the next flowers. Follow Eyebabe and Glengary54.

Banrot is a wettable powder and unless you have commercial sprayers with internal mixing the results can be poor. Wettable powders are not recommended for hand sprayers.

Thiophanate methyl has been recommended for so long to treat Thai Crud that almost all the variates that come in now are immune to it. I find the Vanda just outgrow the disease if given good air circulation and removal of the worst leaves. All the new growth is clean for me.

I also found Subdue is only minimally effective as a cure for Pythium. It is mostly used as a means to control spread of the disease. A pair of scissors cutting the bad leaf is still the best cure. You can usually find the generic in farm supply stores for under $100 a quart, but keep in mind it is not recommended for home use and actually illegal for the dealer to sell it to you.

Subdue does not work on Thai Crud.