Rapid root destruction on Vanda

[Lars Kurth]

Hi,

this Winter I lost some of my large Vanda's through an infection: I am trying to figure out what it was such that I can prevent next year.

I had bought a new plant - I thin imported from Asia - in autumn last year: the plant looked well and had a good root system and had several flower stems. After flowering, the roots started too shrivel and dry out rapidly and the plant started to drop the bottom leaves. I isolated the plant, when I suspected this was a disease but was too late. Eventually until only 6 leaves were left at the top. The disease would slow and then the stem at the top would become soft and topple over. When I dissected one of the affected plants, I noticed that some of the tissue in the stem had slight purple discolouration.

Plants in the vicinity showed similar effects. Roots starting to dry rapidly and leaves shedding. Similar discoloration when cutting through the stem.

I isolated affected plants as good as I could and seemingly I managed to stop the spread of the disease as no new plants have been affected in the last two months. It seems that the disease was spread through wate droplets. I lost 5 of my favourite and large Vandas, which all had excellent root systems and grew and flowered well through previous years. Vanda's which were not affected grew well: which should exclude cultural issues. I tried to use sulfur, Dithane and Systhane all without much effect. A plant would be dead within 5-8 weeks, depending on size.

Does anybody know what this could have been? My main aim is to be able to take preventive action for the next winter. I have been trying to find an explanation on the web, but have not been successful so far.

Regards
Lars