Can algae damage Vanda roots?

[jana]

I live in the tropics (Caribbean) and grow orchids under shadecloth and have a misting system which mists them 3 times a day for 2 - 3 minutes each time. Being at 1200 ft. we have almost continual tradewind breeze.
Over the past year I have been adding Vandas to my collection - they are in hanging baskets and when I get them initially, they have beautiful thick bright white roots with healthy green growing tips. These beautiful roots have been gradually turning light green and the growing tip is no longer healthy. I use RD 20 regularly (once a month). Although they still are green and are blooming, their roots appear to be shrinking.
I am afraid they will lose their roots and die.
Also - any suggestions to induce root formation in Vandas? Help please!! Jana

[MikeWA]

I am by far the Vanda expert but I have heard the new trend by many Vanda growers in Florida is to cut the hanging roots. They used to wrap the roots around the basket. I think Motz was the one who said something about cutting the roots.

Before I answer the rest. What is RD 20?

[jana]

I am by far the Vanda expert but I have heard the new trend by many Vanda growers in Florida is to cut the hanging roots. They used to wrap the roots around the basket. I think Motz was the one who said something about cutting the roots.

Before I answer the rest. What is RD 20?

RD 20 is a general all purpose fungicide/algaecide for garden/greenhouse and can be used diluted on plants. Jana

[LJA]

Jana, algae on roots won't hurt a thing, but the RD-20 can. I use that here too, and if it gets on the roots too frequently, it can dry / burn them, make them shrivel, and cause the root tips to get sunken and brown. Roots turning from bright white to light green doesn't necessarily mean algae; they'll do that as they age when they're watered. Also, they won't always be in active growth, and when they're not, the green, pointed growing tips will just turn blunt and rounded, and somewhat tan. No need to worry yet about losing them, just keep the fungicide off of them when you spray!

Mike, they're cutting the roots off? What in the world for?

[Gin]

It is Motes that talks about cutting the roots , not me, only if they are brown ... dead .. I wonder if it is because they have so many and do it to keep the neighbors roots from growing into the one next to it ? my roots greenish too . Gin

[Charles]

I find this algae to be a problem also. Ed, a vendor, said that algae may keep the roots from absorbing water. This may explain why they shrivel. The plant is actually dehydrating. This would explain why a root can shrivel at the top and remain viable near the bottom. This causes leave loss and eventual death. If there is some algae, it's ok. But when it gets thick, I worry. Algae can also disrupt the root gas exchange.
I don't like algae, but I have not found anything that kills it effectively. Physan 20=useless.

[gbrice]

I grow my vandas outside in almost full light and they don't develop algae. I have however, purchased some vandas that had the roots covered in algae. Under my growing conditions the algae eventually died and dried up and eventually comes off. IMHO I don't think it bothers them that much.

-g

[Cjcorner]

Might it be an air flow sort of problem? I find that my Vandas down here seem to like to wave with the breeze....it keeps them happier for some reason. They like a good breeze almost as much as they like sun and fertilizer solutions....lol Such diva's they are!!
Connie

[kfir from israel]

vandas in the nature grow just like phals with some roots attach to the tree-and sometimes all covered with sphagnum ,the beutifull arachnis that flower now in my greenhouse is full of it!!!!
if some of the roots is demage it my be from over watering or not eanugh humid-heat with good airflow
most of the times vandas will grow new biger roots insted
good luck

[wetfeet101b]

There are very few algae strains that are actually harmful to orchid roots.
*In the water, there are certain strains of phytoplankton responsible for massive marine and freshwater die-off (look for "red tide"). But the dynamics are different on land and air.

Algae killers, fungicides and bactericides applied to the orchids to remove the algae can actually do more harm to the plants than the algae itself.
Most of them are designed to destroy plant cells (last time I checked, orchid plants are made up of plants cells too).

Most algae actually form a symbiotic relationship with the orchids.
1. Orchid roots provide a habitat for the algae.
2. Algae expel excess nutrients from their photosynthetic processes and are absorbed by the orchid roots.
One does not require the other in order to live. However, when paired properly they result in a combination better than the sum of its parts.

a vendor, said that algae may keep the roots from absorbing water

Unless that algae strain somehow hardens into an airtight layer over the roots, this is very unlikely.
In fact, having a layer of moist, nutrient-rich algae on the aerial roots are actually a boon to orchids.

Excess algae growth on the roots may be an indication of improper growing conditions (too wet and not enough air flow).
It is not the algae that killed the roots, the stagnant conditions did. And the algae just happen to thrive there afterwards.

Remember: overwatering plants can also lead to dehydration.

Just like gbrice said, when exposed to proper growing conditions, the excess algae will be unable to sustain itself and die back to a level that balances with the growing conditions.

I don't like algae

Not many people do. Unfortunately, if the growing conditions are conducive to algae growth, the grower does not have much choice in the matter. The algae WILL come and set up shop.
If you do not like the algae, you must address the problem (overall growing conditions) and not just the symptom (excess algae growth).

John