in my opinion it is some thai strain of pseudocercospora or cercospora....i have had experience with this from imported thai plants and since they spray fungicide regularly you would expect a resistance to be built up to many fungicides....Phyton 27!!!!works for sure......

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Quote Originally Posted by wuness View Post
Angela: I've been fighting something like this for the last year or so. I've shown it to several orchid people (on forums and elsewhere), and it's surprising that I get so many different opinions of it. It has particularly devasted my dendrobiums, bulbophyllums and thin-leaved plants. I'm going to treat it as a fungus or bacterial problem and am going to hit it with Bayer Advanced 3in1 according to instructions (i.e., spray three times every 7-14 days). I'm also going to sanitize the greenhouse with a peroxide-based spray and put fungicide in the evaporative cooler. If that doesn't work, I'll have to focus on slipper orchids which seems to be the only group that isn't affected by it.

Needless to say, I feel your pain.

wuness

i feel your pain but Physan out of several fungicides seem to workkk...i had about 50 dendros that had it and all fine now...it retards the plants with that chlorotic nonsense...a friend of mine was fighting with a bacterial rhizome rot of cattleyas alliance...encyclias,catts and even a few reedstems perish within days..large plants lost forever....resistant Phytopthora from thailand once again nothing seems to be working...a new product called Kazumin from Japan recently shows some promise