How often should fungicides be applied?

[Ricardo in PR]

How often fungicides destined to protect the leaves of Paphiopedilums against fungus and botrytis should be applied?

[K Barrett]

What are you using and what's the recommendation on the lable? Assuming you can still read the original lable.

[raybark]

The only preventive treatments I do is a Physan (1 tsp/gal) or bleach (1 oz/gal) spraying every 4- to 6 weeks, primarily to keep algae at bay, but it keeps other fungi quashed, as well.

[Ricardo in PR]

I have not brought yet any fungicide, although I am considering buying Cleary 3336. The subject will be two Paph. sanderianum, one Paph. Prince of Wales and a Paph. phillippinense that used to bloom with seven inflorescences and sometimes produced almost 50 flowers. The leaves of all these plants have become much marked by fungus and botrytis spotted and their health has deteriorated.

[raybark]

If you're going to use a systemic as a curative treatment, definitely follow the instructions on the label.

[Ricardo in PR]

In order to assuage everybody concerns about my use of the fungicide I want to clarify that I plan to be ultra pusillanimously careful on following the instructions on the label. However my question doesn't have anything to do with dosage or thee way one applies the fungicide. I want to know with which frequency growers apply fungicide to their plants so that fungus stays under control and you get those beautiful unspotted leaves that you see on exhibition plants. How often do you apply it? Every month? Once a week? twice a year?

[raybark]

In my opinion, preventive fungicide treatments are sort-of a "last resort" in achieving your goal.

A nice buoyant atmosphere with gentle, but tumbling air movement, proper watering and feeding, and lots of space around plants are the first things to work on.

That said, climate plays a huge roll in the overall effectiveness of those factors, and considering where you are (compared to me, for sure - 9°F PA this morning), your "hand is forced" far more strongly.

As I said before, I would recommend something on the order of Physan or bleach for such treatments, rather than a "big gun" like Cleary's, as the problem is that the fungal spores are ubiquitous, so even if you treat plants to get rid of symptoms, there are a lot more spores where they came from! By spraying the environment, you keep them at bay, if not altogether eliminated.

The Physan folks recommend against adding it to irrigation systems, but one commercial grower I know adds a tiny amount - about 1 ml per 50 liters - to his RO supply that is used for all watering and misting - and claims he has seen no traces of fungi for years.

[Ricardo in PR]

In my case it is a last resort thing as I have tried everything else without good results. My Paph's leaves used to be unmarked but recently they became subject to fungus attacks. I don't intent to do whole collection sprays but to treat individual plants. The type of fungus that is marking and attacking the leaves of the Paphs is not a problem with the rest of my plants. Other Paphiopedilums that are in the general area of the sick plants remain healthy with their leaves unmarked.

[K Barrett]

Originally Posted by Ricardo in PR

I have not brought yet any fungicide, although I am considering buying Cleary 3336. The subject will be two Paph. sanderianum, one Paph. Prince of Wales and a Paph. phillippinense that used to bloom with seven inflorescences and sometimes produced almost 50 flowers. The leaves of all these plants have become much marked by fungus and botrytis spotted and their health has deteriorated.

Well I'm going to be the contrarian here and suggest that the fungus might be an indication of greater problems - that is to say root problems. If all the paphs in and around these 4 plants are healthy then you gotta wonder what's up with these guys? Sometimes broken or fractured roots allow bacteria and fungi to enter the plant through these breaks and wear the plant down. Plants that produce up to 50 flowers sound (to me) like they are specimen sized, and (maybe I should speak for myself) I'm loathe to repot a specimen sized plant. Or maybe last time you repotted you repotted into some medium the plants don't like or maybe a helper repotted these too firmly and broke more roots than they thought? Or maybe you decided to start standing them in water and they didn't like it. I dunno, I'm just guessing here. These are all from the same section of Paphiopedilum (IIRC, I could be wrong), so I'm going with potting & culture rather than creeping crud. I'd repot. Maybe Physan the roots though that's not my usual habit. I usually depend on the fact that I got the plant out a cruddy medium and they should breathe easier, sending out new roots and shoots.

Just my 2 cents.

[K Barrett]

Originally Posted by raybark

As I said before, I would recommend something on the order of Physan or bleach for such treatments, rather than a "big gun" like Cleary's, as the problem is that the fungal spores are ubiquitous, so even if you treat plants to get rid of symptoms, there are a lot more spores where they came from! By spraying the environment, you keep them at bay, if not altogether eliminated.

That's why I can't understand why its only these 4 plants. Spores are everywhere. Bob Gordon once wrote if you have a buoyant atmosphere and good air movement its kinda hard for a spore to land on a plant if its travelling by at 30 mph (or however fast a fan blows). The Hawaiian dendrobium growers talk of whole crops turning to mush overnight once a fungus starts, once you see the fruiting bodies its too late. So I think its something else, the spotting is from something else. But quien sabe?