My Oncidium roots are molding, leaves turning yellow

[King_of_orchid_growing:)]

Originally Posted by BobInBonita

...permanganate is the strongest oxidizing agent of the three. In laboratory use more protective gear was required to use concentrated permanganate solutions although it was used as an antiseptic (especially veterinary) prior to antibiotics. a side effect is that it will stain whatever it touches purple.

...The permanganate will leave both potassium and manganese salts behind.

Good to know. I didn't know that. Thank you.

Originally Posted by BobInBonita

If you're worried about fungi, why not use a fungicide designed for plants. Many are commonly available at garden centers

Phyton 27 is one of those fungicides.

[King_of_orchid_growing:)]

Originally Posted by King_of_orchid_growing:)

Although not potent, it does kill cells (I didn't dream this up, I had a botany instructor mention this to the entire class during lab as a kind of fun fact). It kind of has a very weak bleaching effect. You can try it out if you like, on your own fingers (I wouldn't do it repeatedly over an extended period of time though).

I re-read this, and feel I have to make an edit, especially after reading the following:

Originally Posted by BobInBonita

Bleach, peroxide, and potassium permanganate are all POTENT oxidizers.

edit: Peroxide is not as potent as bleach.

That was the point I wanted to get at.

So yes, "BobInBonita" is correct in his descriptions...

Originally Posted by BobInBonita

In terms of oxidizing power, the household peroxide at 3% is the gentlest, Chlorine is a much stronger agent, ...permanganate is the strongest oxidizing agent of the three...

[grasshopper]

Regardless of what you decide to do with the Physan 20 or peroxide, I would recommend better air flow in your growing environment. This should help quite a bit. I've not had good experiences with the indoor greenhouses...they are great for improving humidity but do not allow for much airflow. Maybe try a small clip fan to circulate the air a little better.

If you get a fan, you may need to up your watering schedule to 2x a week, as the plants may dry out a little faster with better air flow.

Hope this helps!

[Orchid126]

You are making it sound as though I advised WaterWorksGS to pour straight chlorine bleach onto his roots. I did not. I suggested a teaspoon to a quart. This comes out to four teaspoons to a gallon, probably even less than the one ounce to a gallon that FirstRay's site suggests.

And H202 is half oxygen. It isn't a by-productof the combination, but an integral part of the orginal formula--two molecules of hydrogen and two molecules of oxygen=hydrogen peroxide. You make it sound like it's poison.

You went into a state of panic without giving attention to what I was actually suggesting.

[WaterWorksGS]

Thank you all for your great advice you have given me. I used 1 part peroxide to 1 part water to the roots on the one that looks the worse, just as a trail to see what happens. I think I may take CTS's advice and wait until Physan gets here to use on the rest. I will give you all an update soon, thanks again

[Ray]

You need not have bothered diluting the hydrogen peroxide. The 3% stuff sold at the store will not damage the plant at all. In fact, some growers pour it through potting media in order to provide extra oxygen to the plants' roots (2H2O2 → 2H2O + O2, as King mentioned). Alan Koch of Gold Country Orchids told me he "buys it by the pallet load". There are even products on the market for that specifically, and they're just hydrogen peroxide, so why pay extra. (And if you pot your plants up correctly, air flow is not an issue, anyway.)

Before "discovering" Physan, I drenched my greenhouse regularly with liquid chlorine bleach diluted at one ounce per gallon, and never saw any problems.

[BobInBonita]

In my opinion, we have all taken a narrow thought and applied it broadly. Everyone is correct.

Good growing conditions obviate the need for most, if not all, treatment.

If treatment is needed, focusing on the thing that needs to be addressed is best. A specific (targeted) fungicide for a fungal problem, etc.

Non-specific agents (like oxidizers) attack all organic materials. Dilution and contact time is key. Just because they will break ANY double bond they contact does not mean they should never be used. Their very strength is what sometimes makes them safe.

Chlorine at low dilution is perfectly safe, at high dilution it is toxic. I drink and frequently water with chlorinated drinking water. Straight bleach will kill any orchid submerged. Dilution is key. Chlorine is "used" when it reacts and breaks a double bond. Because a single cell fungus presents more surface area than an orchid root, most of the destructive action is on the smaller particles (with high surface area to mass ratios). Poured through media, most dilute chlorine is used before it has a chance to damage the root.

Peroxide at 3% is pretty darn safe (I would wash my hands in it without a second thought), but I have personally been seriously blistered (instantly) by accidental contact with industrial 30% peroxide. Many bacteria have a peroxidase enzyme that breaks down peroxide instantly (the fizz when it bubbles).

Again, everyone is correct, and I apologize if my narrow comments were interpreted too broadly. I did NOT mean it as an indictment of their growing style or chemical use. I promise to try to be more clear in any future posts.

[WaterWorksGS]

Just yesterday I soaked my ladies in 2tsp:1gal Physan 20 and water. I also sprayed them with it also. This is what they look like today. They don't look so good but I don't think any of them are doomed yet...i hope. I'm not sure if they have multiple diseases, looks like it??

[BobInBonita]

Sounds like you are doing all the right things. Now it's up to time. Be consistent in your care, and they should be blooming in no time. I remember you repotted to hydroton, but don't remember what they were in originally. If it was a change in media, there may be a temporary slip before the bounce-back. It's not as significant with a LECA product, if they were in bark the media might be a bit high on the PB.

Best of luck and keep us posted.

[WaterWorksGS]

It has been a almost a month since I first posted. The roots and fungus problem seems to be better. I still have 2 of my ladies that are not doing so good. The pbulbs on them are wrinkling and some of the leaves are turning yellow. They are in S/H and with that it needs to be watered almost daily and I give the top a mist 1-2 times daily. I'm not sure if that is too much but the hydroton and roots seems to be rather dry when I check on them in the morning. They never sit in water it drains out. My humidity here is 35-45%. I tried letting them sit in water for 24hrs and it didn't do anything to help the shriveling. Any help would be appreciated as to what I'm doing wrong or not doing???