Using Fungicide

[mia1aab]

I have about 30 orchids (mostly cattleya's and vandas) and have no idea when and how often to spray them with fungicide. Right now the rainy season is in full gear in South Florida and I want to make sure the plants stay healthy. I bought a powdered fungicide this past weekend. When and how often should I apply? I was told once a week at 1/2 strength until the plants become acclimated. Is this correct? Thanks!

[FLBob]

Never use fungicide or insecticide at anything other than full strength. That is a sure way to create super bugs that can not be controlled.

[jerrymeola]

I would never use any fungicide more than twice maybe three times a year.

Fugal problems adapt to be immune to the fungicide and then you have super resistant strains.

Most of the ones sold to hobbyist are no longer effective against the strains we have now. The strong ones are illegal to sell for home use although you can probably get them. Keep in mind they can kill you as well as the fungus.

The most recent and effective fungicides are $300-$500 dollars each and need to rotate at least three types.

The best cure for fungus is to prevent it in the first place.

Good air circulation is the best prevention. Fungal spores live in the grass and yard plants. Keep your plants strong and they will resist fungal infections.

Badly decomposing bark breeds fungus so change bark at least every other year in Cattleya and orchids that take hard drying. Moist plants like Phals should be changed every year.

I like using bracilus subtilus bacteria which is a natural anti fungal inoculate. After using it for a year the number of plants attacked by fungus dropped 85%. I get it in Companion brand made from seaweed.

Powder fungicides are very difficult to apply and most do not recommend their use in less than 50 gallon mixes. They should also be sprayed with a sprayer that has a constant mixer in the tank, which is not somoething you will have at home.

[willowbanks]

mia1aab, what is the brand name of the powder fungicide you have???? (or the active ingredient)

Bill

[kmarch]

I only use fungicides in 2 cases:
1) when I deflask new seedlings, I give them a spray with Mancozeb (an Aussie fungicide) after they've been potted up, and
2) when I have a persistent, threatening fungal infection on a plant, and then I usually only spray the infected plant.

Once a week sounds like it's really a lot. I don't even know any commercial growers who spray fungicide that often.

[willowbanks]

Kevin, I know you are a proud Australian now but we can't steal the credit for Mancozeb, it was first registered in the United States in 1948. This fungicide is common world wide under many brand names.

Bill

[Brooke]

Mia the Macozeb is easily attainable to hobby growers plus Bayer has several different fungicides available for home use. The directions will tell you how to apply and as FlBob said, use at the recommended strength.

If you are going to use these as preventatives, you will need to rotate different fungicides.

Brooke

[Ron]

The best cure for fungus is to prevent it in the first place.

Good air circulation is the best prevention. Fungal spores live in the grass and yard plants. Keep your plants strong and they will resist fungal infections.

Badly decomposing bark breeds fungus so change bark at least every other year in Cattleya and orchids that take hard drying. Moist plants like Phals should be changed every year.

Hi, I agree with Jerry on this one.
A well maintained collection with good ventilation should not have fungal problems even in the warm humid season.
Watering in the morning and allowing the plants foliage to dry out before nightfall with help solve the problem in a big way.
In all the years of growing orchids I have never had fungal problems, once I improved my growing area and conditions.
Only fungicide I use is in deflasking as a preventive measure, as often flasks can cost up to AUD$300, one can not afford to take chances with these.
Good growing
Ron

[digitalgate]

unfortunately , it depend on the area one reside for this method to work. I stay near coast which make thing worst. High humidity and sometime very little air movement and huge area make putting a fan or two not feasible. Worst is the Town council refuse to move or cut down any trees that is blocking the wind. Torrential rain that rain for days refuse to let up make matter worst. So naturally fungicides is a must for a person like me. missing fungicides schedule regiment would mean certain death for the plant.
The good news is there is so many we can use as fungicdes as fungus need a good pH to grow well. Sulphur, baking soda, physan20 can tip the pH and discourage some fungus from establishing itself on the plant. a swing in pH will make sure not one fungus will be the dominant type (hopefully the good ones will stay). Adding fungicides to the list will make sure things dont go too far before it kills a good plant. That just my 1 cent worth.