Thursday, January 13, 2011

Disa Rot

Apparently the biggest problem with growing Disas is their susceptibility to fungi. How the little blighters ever manage to grow in the wild is a mystery!

One of the Disas we bought at La Motte was stricken with "Disa rot" whilst in our care, where some bacterium or (more commonly) fungus starts chomping away at the roots. Underground. Where you can't see it. The next thing you know, the leaves start turning yellow. We tried two doses of Efekto's Fungi Nil 500 WP (500g/kg Captab [Dicarboximide]) at 4g/l, but the plant looked more and more sad.

Last night, after potting up some flasked, micropropagated Disa bivalvata, I decided to have a look at the orchid underground and see how things were getting on.

I was dismayed to see just how far the rot had gone; pretty much all the above ground plants had rotted clean through where they join up to the roots/tubers - the flowering stem pretty much fell right off when I removed the plant from its pot. I managed to find one tiny shoot and tuber (with no intact roots) that looked like it might make it; everything else was blackened and had rotted right through. :(

Disa Rot: The surface signs
Disa Rot: Noooooo! My Plants!!!! :( You can see the tubers and the shoots and how it rots right through the middle.
Disa Rot: Up close and personal. Yuck!
Sad looking flowers; you'll note that the seed pod was swelling, so our efforts at pollination had worked. :(
All that remains... (the background is kitchen towel, so you can see just how small this was)
After leaving the tiny little plantlet soaking in fungicide for a while, I repotted it into fresh Disa potting mix and watered it with 4g/l Fungi Nil. Hopefully it will make it, but I don't hold out much hope :( Most Disa growers seem to recommend regular "preventative" anti-fungal treatments - looks like they're definitely needed...