Vanda problems

[Yoshie]

Hello. I'm new to the forum and have a problem.

I have been growing vandas for about 5 years. I have a greenhouse with over 100 of the plants here in Oklahoma. They have always done very well until about a year ago.

The root tips turn black and shrivel back about 2 inches, then they lose several lower leaves. Then they send out new growing tips that grow several inches, only to have the same die back process start all over again. My beautiful plants have lost half their leaves and I'm afraid they will eventually all die. I've lost 5 already.

I have talked to a vanda grower in Florida who has had the same problem with no idea what the cause is.

Can anyone help me?