Dithane m-45 how to use - Orchid Board

Zoren · #1 06-10-2018, 05:21 PM

Dithane m-45 how to use
I bought 2 new Phalaenopsis species: Bellina (1 spike with almost blooming bud with a second bud about to come out and Cornu cervi with I think 6 spikes, I got them from RF Orchids in Homestead Florida. Geo of RF Orchids informed me that the Cornu cervi has a small 'leaf fungus' and sold me Dithane m-45 to be apply it to the plant. The instructions he gave me are 1 tablespoon of powder to 1 gallon of water, to be applied every 10 days for about a month or as long as it takes to get rid of the leaf fungus. I have no experience with this product and the instructions to not very understandable. I also would like to know if I can spray all my orchids even if they don't have a fungus or mold. Is it safe to use the product as a form of protection. Do any senior or any member have any experience with this product. I could use some help from anyone out there!! Zoren...

King_of_orchid_growing:) · #2 06-11-2018, 03:53 AM

Dithane M-45 is a contact fungicide that is primarily used as a preventative measure against a wide array of fungal species. Although it is a broad spectrum fungicide, it does have limitations on which species it is good at protecting the plant against.

The following link provides some basic information of what this fungicide does:

Dithane(R) M45 | India | Dow AgroSciences

In case you were wondering what a contact fungicide was and the basics of its mode of action is, then this should help a little bit:

Contact Fungicides - Turf Management - Bayer

Should you still be interested in using Dithane M-45 as a form of treatment, then you should follow the instructions printed on the label of the bottle on how to prepare it.

You may use it as a spray or a bath. If you spray, you may have to spray both sides of the leaf. If you use it as a bath, the entirety of the plant will be in contact with the fungicide. When the leaves dry, it'll probably leave behind a white deposit that resembles the hard water deposits on glass shower doors.

Dithane M-45 does not appear to have good curative properties for fungal diseases.

If you were truly interested in a fungicide with curative properties, then a systemic fungicide such as Thiomyl would've been a better choice.

If you're wondering what a systemic fungicide is and the basic idea of its mode of action is, then this link should help give you a basic understanding:

Systemic Fungicides - Bayer Environmental Science

Another general group of fungicides to consider in your case might be the mesostemic fungicides because the affliction is on the orchid's leaf:

Mesostemic Fungicides - Bayer Environmental Science

You can keep the Dithane M-45 as a back-up if you'd like, but it probably wasn't really necessary.

One other thing to consider is that these fungicides are only good against true fungi. There are a few imposter fungi called oomycetes that are not true fungi, but rather are a special kind of algae that superficially look like fungi. These organisms are treated differently. While it is not easy to determine whether what your plant has is a true fungi or if it is a oomycete, this is a factor to consider when choosing a treatment strategy.

Just how bad is this fungal infection on the leaf of your newly purchased Phalaenopsis cornu-cervi anyways? Are you able to provide a photo?

Zoren · #3 06-11-2018, 08:21 AM

Thank you Philip, I looked into the links you suggested the information was very informative. I don't think the water fungus (that's what F Orchids said it is) is bad at all, I will try to send a few pictures. I see only a few black dots on a few leaves (nothing on the underside of the leaves). So, I guess I can spray all my flowers as a protective measure without worrying the spray will harm harm them? I have never had any experience with fungus or any other type of bug or mold problems (only root-rot --my fault) So again thank you for your help..Zoren..

King_of_orchid_growing:) · #4 06-11-2018, 10:12 AM

The reason why I suggested that it is best to not use Dithane M-45 as a preventative is because the idea is to let the plant's own immune system do what it's supposed to do - protect the plant against pathogens.

It really isn't necessary to keep applying the fungicide even as a preventative in this particular instance.

Like I said earlier, in my opinion, it'd probably be best to keep the fungicide as a back up for when you actually do need it.

Phalaenopsis cornu-cervi is one of the easier species to grow. You'll find that you won't have such a difficult time with this one. I wouldn't worry much about this species.

Those leaf blemishes are not worrisome to me.

estación seca · #5 06-11-2018, 03:32 PM

The whitish spots are from minerals in the water. The same thing happens if you spray water on a window and let it dry. That is not a problem.

I don't see any spots I would worry about, unless they begin to spread. I personally would not treat this plant with a fungicide. Are you growing them indoors where it is air conditioned, or outdoors? What is the approximate humidity where you are growing them?

Zoren · #6 06-11-2018, 04:41 PM

I live in South Florida and grow my plants in the sun room, the humidity is usually high and the temperature is high, but, When I turn on the AC it all evens out. I keep the AC at about 86 F during the day and about 76 F at night. I only run the AC during the day when the temperature climbs toward 88-90 F (which is most of the year). I'm on the 4th floor of a condo and my windows face SW-SSW and the building is at an angle that usually doesn't allow much of a breeze (I compensate with ceiling fan at maximum, and three window type fans at various speeds and of course the portable AC...Zoren...

estación seca · #7 06-11-2018, 05:08 PM

It's probably not excessively humid in the condo if you use the air conditioning from time to time. I would wait and watch the spots rather than treat now. Floridians do have a lot more trouble with fungus than do people in other places.

Zoren · #8 06-11-2018, 06:52 PM

I have never had a problem with fungus, until (only at the suggestion of RF Orchids) when I purchased 2 Species Phalaenopsis: A Bellina in double spike with a bud (no fungus) and a Cornu cevi with 6 spikes with one bud (water spot fungus) that's what he said the small black spots were. I think that they sell you the fungicide as a protection because they grow all there orchids in an open air greenhouse and the leaves get wet. I grow my orchids in an almost completely dry sun room environment (I do mist the orchids at times). I keep the room at about 86 F during the day (most of the time the AC is off during the day and at 11 pm I turn the AC temperature down to 75 F at night (for a 10 degree difference) until 7 am the next day, back to 86 F.. Thank you for your input...Zoren...