# Algae over leaves



## Guarceñosis (Nov 13, 2018)

I suffer a lot of this yellow algae over orchids leaves surface. Does any one has experience how to control it or erradicate it? Thanks.


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## abax (Nov 14, 2018)

I know it's a boring job and takes time, but using a diluted insecticidal soap as
a wipe works well and discourages the return of the algae.


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## ehanes7612 (Nov 14, 2018)

algae on leaves is caused by excessive humidity or leaves not drying out fast enough mixed with too much shade...I live in the Northwest US , we all know too much about this, algae grows everywhere in the wintertime...more circulation of air could help ...more light ..anything so that it dries out faster


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## Ozpaph (Nov 14, 2018)

ive never seen that before.


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## TyroneGenade (Nov 14, 2018)

Spray with dilute bleach (10 ml/l) or hydrogen peroxide (3%). If you don't fix the humidity issues then the algae will grow back.


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## ehanes7612 (Nov 14, 2018)

Ozpaph said:


> ive never seen that before.



that's because the sun always shines in Brisbane , right?


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## CarlG (Nov 14, 2018)

Perhaps a quarternary ammonium compound (like Physan) would work better - that is more likely to disrupt the algae cells, while having less effect on the orchid leaves' cuticle.

The Physan bottle claims that it is non-phytotoxic, which seems counter to claims of being an algicide, however.

From a google search for physan:
"Physan20 is a broad range disinfectant, fungicide, virucide, and algaecide which effectively controls a wide variety of pathogens on hard surfaces and plants"

Of course, I've seen marble being called organic, so go figure...


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## Ozpaph (Nov 15, 2018)

ehanes7612 said:


> that's because the sun always shines in Brisbane , right?



It light at 0445 at the moment!


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## Guarceñosis (Nov 16, 2018)

Thanks to all. I live in the tropic at 7200 ft asl. In rainy season the humididy can reach 96%, which can't control.

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## Guarceñosis (Nov 22, 2018)

CarlG said:


> Perhaps a quarternary ammonium compound (like Physan) would work better - that is more likely to disrupt the algae cells, while having less effect on the orchid leaves' cuticle.
> 
> The Physan bottle claims that it is non-phytotoxic, which seems counter to claims of being an algicide, however.
> 
> ...


Any idea of the dosage? Tks.

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## CarlG (Nov 22, 2018)

I'd start with perhaps 1cc per liter.


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## Guarceñosis (Nov 23, 2018)

CarlG said:


> I'd start with perhaps 1cc per liter.


Thanks a lot

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