large collection with problems - Orchid Board

Stray59 · #1 02-21-2015, 08:58 PM

Hello everyone......
I have been working with a local museum greenhouse. A benefactor gave, a large orchid collection to the greenhouse several decades ago; over the years various levels of care led to a large number of them started to develop infections. The new management and the heirs of the original donor have decided to bring in some "new blood". Unfortunately, many of the new ones have developed suspicious yellow spots and variants of coloration in general. I am posting some photos.....would appreciate your input about what some of this might be.....bacterial, fungus, or viral.
I realize that the best thing would be to test all of the collection but there are hundreds of plants and the cost is truly inhibitive.
My suggestion - if they look bad, pitch and replace, but some of these are new additions from what has always been a reliably disease-free wholesale grower.
Ideas? Some look like they have sun burn, but the yellow spots and odd patterns have me wary.

Orchid Whisperer · #2 02-22-2015, 12:30 AM

2nd & 3rd photos could be sunburn.

If you suspect some plants are virused, testing is the only way to confirm.

Why not set a budget for testing some suspicious plants? I'd start with ones you are most suspicious of, maybe plants that also meet another criteria (eg, newly purchased, maybe a refund possible; or test the plants that are hardest to replace first?). If you get positives for virus, time to start culling plants.

Stray59 · #3 02-22-2015, 01:33 AM

Orchidwhisperer-
Thanks for the input .... I am hoping that a lot of what I see is a result of poor shading practices or perhaps chlorosis. The collection has seen years of poor handling, fertilizing, re-potting - you name it and it was probably lacking. Thankfully, that has changed.
I do know the definitive way to be sure is testing - but we would be talking around 250 - 300 plants that would all have to be tested. The people in control of the money do not understand that viral orchids need to be immediately thrown, so the money is the issue here. I was just hoping for a little good new, I guess......
Thanks for looking!

Orchid Whisperer · #4 02-22-2015, 08:13 AM

I understand.

I wish there was a way to diagnose by looking, but there are fungal.problems that can look viral, and some viruses that look like bacterial, fungal, or mesophyll collapse problems.

silken · #5 02-22-2015, 11:48 AM

I agree that the only way to know for sure is testing.

But I just tested 21 of my most suspicious orchids. Some with spots and not looking nice. Surprisingly almost every one that tested postitive (for OSRV and CMV) were the spotless, healthy actively growing ones with good roots. Not the ones with ugly marks which I will now assume is either a calcium deficiency or bacterial or fungal. The reason I tested some pristine looking plants was because they should have bloomed by now and haven't. I was rather surprised.

Maybe if you can segregate the most suspicious and give them a good systemic bacterial/fungal treatment and good care, it will help you decide if they still appear virused 6 months or a year from now.

As well, if some of those bloom with colour break then you can maybe assume they have virus and toss them. But things like systemic treatments can cause that as well. I think being treated with imidacloprid for scale can cause colour break for a year or two after treatment in some cases. It happened to one of my Oncidiums.

Stray59 · #6 02-22-2015, 07:07 PM

Yeah, the insect issue is a just that - an issue. The current greenhouse manager is very environmentally conscientious, which is great, but, she has a very strict and negative attitude about chemicals in general, so they have not used any regular spraying program for insects. This leads to regular outbreaks of mealybugs and scale. The employees utilize soap and water, then alcohol swabs to remove the insects by hand. This just does not get down into the tiny cracks and dead growth sheaths that orchids are loaded with. I believe that this may change as they may just have to make some changes to have the collection they want.....
Thanks for the ideas - much to think about here and more to overcome....

silken · #7 02-22-2015, 07:17 PM

Quote:

Originally Posted by Stray59

Yeah, the insect issue is a just that - an issue. The current greenhouse manager is very environmentally conscientious, which is great, but, she has a very strict and negative attitude about chemicals in general, so they have not used any regular spraying program for insects. This leads to regular outbreaks of mealybugs and scale. The employees utilize soap and water, then alcohol swabs to remove the insects by hand. This just does not get down into the tiny cracks and dead growth sheaths that orchids are loaded with. I believe that this may change as they may just have to make some changes to have the collection they want.....
Thanks for the ideas - much to think about here and more to overcome....

Good luck. It's too bad some people have such a black and white attitude about some things. I don't think all chemicals can be called bad. If they are used responsibly then they serve a good purpose. Insects can spread disease among plants. So allowing them to thrive with no active control program is not good either.

Stray59 · #8 02-22-2015, 11:57 PM

Yeah, I totally agree Silken, and we are slowly trying to show the benefits of responsible use of chemicals as needed. We'll see!
Have a great week everyone!