Odd stain on Oncidium leaf

[Ray]

Originally Posted by Karen00

You also asked about how much I diluted the fertilizer. I'd say I probably dose at just 15% (maybe less) of what the general dosage instructions say. Having said that I'm using a general fertilizer not one specifically for orchids. I've been dosing this way for three years and haven't had issues but of course every plant is different.

Thanks!

Unfortunately, 15% of an unknown concentration tells me nothing. "General dosage recommendations" vary all over the map. Let's not forget that a fertilizer manufacturer makes money telling you to use more fertilizer, while orchids are VERY undemanding of it.

[Karen00]

Originally Posted by Ray

Unfortunately, 15% of an unknown concentration tells me nothing. "General dosage recommendations" vary all over the map. Let's not forget that a fertilizer manufacturer makes money telling you to use more fertilizer, while orchids are VERY undemanding of it.

Sorry. I wasn't trying to be precise. Just trying to indicate that I wasn't using full strength and I only fertilize when flower spikes appear. I don't fertilize for leaves or after the flower buds have opened.

Full strength for the type I have is 20 ml/5 liters of water (4 tsp/1.3 gallons)

I'm doing about 15% ferts in the same amount of water.

[Ray]

First of all, the plant needs fertilizer - not a lot, but some - ALL OF THE TIME, not just when spiking. If you're only feeding that infrequently, you're starving your plants.

I'm just trying to pass on 45+ years of orchid-growing experience here, and again I have to say, knowing that the manufacturer recommends 4ml/L - without knowing what the fertilizer formula is - tells me nothing upon which I might do so.

For example, if the fertilizer has 5% N, 4ml/L would be providing about 200 ppm N, so your "15%" level or 30 ppm N would be excellent for using on the plants every time you watered, assuming you water them about twice a week. On the other hand, if it is a 20%N formula, with the same "recommended" and "as you use it" levels, you'd be at about 120 ppm N, which would be appropriate for orchids if fed once every two weeks.

[PaphioAdict]

Originally Posted by Ray

Systemics may stop the progression of an infection, but that damaged tissue will not be repaired.

Oh good to know. I am hesitant to use systemics since we are mostly organic gardeners around here. However when it comes too brown rot and such then the mean ones are necessary or at least that has been my experience.

[Karen00]

Originally Posted by PaphioAdict

Oh good to know. I am hesitant to use systemics since we are mostly organic gardeners around here. However when it comes too brown rot and such then the mean ones are necessary or at least that has been my experience.

I think, in some cases, systemics might be needed if an infection has taken hold of a large part of the plant or worse the entire plant and cutting back the leaves would do more harm than good. Whether the systemic works or not is a different story.

I think systemics also serve their purpose if the infection can't be treated topically. As an example, in my case there were no external issues with the leaf and I don't think anything topical would get down into the lower cells where the infection was lurking. I tried wiping the leaf with hydrogen peroxide and isopropyl alcohol and it did nothing. Thankfully it was just one leaf so cutting it seems to have stopped it with no adverse impact on the plant. Had this been in most of the plant I think a systemic would have been needed.

Just my humble opinion of course. :-)