Guignardia!! Questions after digging through the board

[WarrenG]

Happy New Year all! With the cold weather here in North Carolina i have had 2 plants show signs of the dreaded Thai Crud. I have done a great deal of reading and researching online and have come up more confused than ever: what compounds can i use to control it in my greenhouse? The two plants in question are full of sentimental attachment, so I’d really rather not destroy them unless absolutely necessary. Thiomyl? Daconil? Triforine? Propicanizole? What will help?

[Ray]

Unless you're talking about dendrobiums or thin-leaved plants like coelogyne, huntleya, etc., I would recommend a copper-based treatment (Phyton, Southern Ag Liquid Copper, etc.) for a couple of reasons:

1) It's cheap.
2) Diagnosing diseases from appearance is very difficult, and copper compounds can kill a broad range of bacterial and fungal pathogens.

If the plants or your preferences rule out copper and you're reasonably certain about the diagnosis, I'd recommend Thiomyl or Cleary's 3336.

[Louis_W]

What is Thai Crud??

[estación seca]

Guignardia and Phyllosticta are names given to two different life phases of the same fungus.

Phyllosticta Leaf Spot

Orchid Diseases

[Toadwally]

Originally Posted by estación seca

Guignardia and Phyllosticta are names given to two different life phases of the same fungus.

Phyllosticta Leaf Spot

Orchid Diseases

How often would you fungacide treat a severe case in a Vanda?

[Ray]

Originally Posted by Toadwally

How often would you fungacide treat a severe case in a Vanda?

I'd follow the recommendations on the label. For example, the Southern Ag Liquid Copper calls for 2 teaspoons/gallon at 7-14-day intervals.

[Toadwally]

Originally Posted by Ray

I'd follow the recommendations on the label. For example, the Southern Ag Liquid Copper calls for 2 teaspoons/gallon at 7-14-day intervals.

Thanks. Will do. All not showing except for one that is riddled.

[Orchonubee]

Something I learned in growing mangoes is that copper, daconil, abound and other similar products are preventatives, not cures.

I DID FIND THIS ON THE INTERNET:

How to Naturally Kill Fungus on Plants

Prepare a solution of 1 part 3-percent hydrogen peroxide and 9 parts water, in a spray bottle. Lightly spray the plants affected by the fungus.
Fill a spray bottle with 1 part skim milk to 9 parts water. Spray the milk solution on the plants, liberally, to kill fungus.
Apply a baking soda solution to kill plant fungus. ..

[estación seca]

Guignardia/Phyllosticta live inside the plant tissues. The spots are the fruiting bodies, which emerge to spread spores into the air. Only a systemic fungicide can have a chance at eradicating the infection. From what I've read it's almost impossible to eradicate from an infected plant.

Proper growing conditions and mechanical measures (like painting clear nail polish on the spots) might prevent it from infecting other plants, but growers need to think about getting rid of the plant.

[Toadwally]

Originally Posted by estación seca

Guignardia/Phyllosticta live inside the plant tissues. The spots are the fruiting bodies, which emerge to spread spores into the air. Only a systemic fungicide can have a chance at eradicating the infection. From what I've read it's almost impossible to eradicate from an infected plant.

Proper growing conditions and mechanical measures (like painting clear nail polish on the spots) might prevent it from infecting other plants, but growers need to think about getting rid of the plant.

I just purchased a thiofanate-methyl-based fungacide suggested by Marty Motes for this very one. One of my vandas is covered with it. Will see what happens.