Help, please. Does this look bacterial? Or what is it??

[eds]

If you have a large collection you need to test, can you approach testing by grouping and sampling several plants with a single test to narrow down possible infected plants (and potentially reduce the number of tests you'd have to employ in the process)?

For example, if I have five new plants coming in, is it feasible to take samples from those five to put into a single test to determine if the whole lot might be virus-free without having to use five tests? So, if the results are negative, you can set aside all five plants as ok. If it's positive, you'd then need to test individually, of course.

I don't know if this can work, but maybe someone has experience with an approach like this.

I initiated a similar approach when I worked at a microbiology lab many years ago. Instead of testing each sample for Salmonella I pooled samples and then retested any positive pools. I cut the cost of testing to nearly a fifth. However I had a good idea of the average rates of positives from previous testing to be able to work out a reasonable pool size. Get this wrong and put too many plants in and all your pools will come back positive needing more tests! Do too few and you'll barely save enough to warrant the time to retest!

It might be worth picking 10 plants at random and testing them first to establish how widespread any virus might be in your collection before seeing whether pooling would save you any money.

 

[southernbelle]

I bought the Rega test kits on eBay and they were not cheaper. The strips results were slower to develop and much harder to read.
The Agdia strips show results as soon as the control line develops. Sometimes one of the virus line results will be a little lighter than the control line, but always unequivocal, whereas the Rega results left me squinting and holding them up to sunlight.

Good to know, thanks.

 

[Teresa Koncolor]

If you have a large collection you need to test, can you approach testing by grouping and sampling several plants with a single test to narrow down possible infected plants (and potentially reduce the number of tests you'd have to employ in the process)?

For example, if I have five new plants coming in, is it feasible to take samples from those five to put into a single test to determine if the whole lot might be virus-free without having to use five tests? So, if the results are negative, you can set aside all five plants as ok. If it's positive, you'd then need to test individually, of course.

I don't know if this can work, but maybe someone has experience with an approach like this.

https://www.aeorchids.com/orchid-culture/orchid-virus-testing/
That link is to an article where they test up to 6 plants together. I did it and it worked. I grouped the paphs since they have a low positive rate. When I tried grouping others then it was a waste because I'd have a positive and have to run all 6 plants separately.

 

[southernbelle]

This idea actually ran through my head after Fauci mentioned it for COVID. The process of smashing up the leaf and mixing it with the buffer solution so that the solution will still run through the test strip with enough material from all the plants is my only concern.. leaf tips vary greatly, some thin some thick. by the time you smash everything up, you have a green soup with probably a higher viscosity? Not sure at what number plant this method would fail to run correctly. I would probably be comfortable testing 2 at a time myself.

Pete, I was thinking how hard it would be to test a bunch, as it says to use a sample the size of a quarter dollar. Also, that too large or small a sample could render the test invalid. So if you need a quarter size sample of one to be accurate (not too large or too small), I don’t see how you could use multiple samples and not destroy the integrity of the test.

 

[southernbelle]

Wow. NP, I hope you were able to rest up and your recovery is quick. It's amazing how fast the recovery for these procedures are these day. Some I have heard are even outpatient procedures, which blows my mind.

BTW, I laminated all the charts you sent me, and have them next to my monitor. On breaks I review the tables to see how I can best use the info for the collection. I'll use them for the rest of my life.. Thank you so much for organizing and sending those to me!

Pete

I’m doing well thanks. One night in hospital, home 2 days. Each day I walk better on the walker, of course. No pain at all unless I walk too much (which isn’t much right now), then the muscles scream. One day at a time.
Glad you are enjoying the charts. Did you see my reply To your post above from Sunday about the sources of virus spread? I have a question there. I will repeat it here:

Pete, I thought virus was only spread through plant sap. Using clippers on one plant, then another without sanitizing or not properly sanitizing pots when reusing. I see the stake thing since you could pierce a root with a stake, but some of the other examples I had no idea about. Also, some insects I think can spread them.

 

[southernbelle]

Mistake

 

[PeteM]

Pete, I was thinking how hard it would be to test a bunch, as it says to use a sample the size of a quarter dollar. Also, that too large or small a sample could render the test invalid. So if you need a quarter size sample of one to be accurate (not too large or too small), I don’t see how you could use multiple samples and not destroy the integrity of the test.

Yes. I think you are correct. I doubt we would be able to test more that two and be comfortable with the results without testing the method first, who knows at what point the test would really break down. The best way to find out is to have a plant that tested positive and run tests with it by retesting it with multiple plants.

I believe that you could easily get away with ‘pooling’ only two plants into one test. They probably design their test to provide a certain margin of error to account for the size and thickness of the plant material. It is after all the only variable that changes between their tests.. the size of the plant material cut by the user.

So my thought is, if you could get away with testing just two at a time, that in itself drops the cost of the tests in half, to something that is a little more reasonable for people with a collection of our size.

 

[PeteM]

Yes. I think you are correct. I doubt we would be able to test more that two and be comfortable with the results without testing the method first, who knows at what point the test would really break down. The best way to find out is to have a plant that tested positive and run tests with it by retesting it with multiple plants.

I believe that you could easily get away with ‘pooling’ only two plants into one test. They probably design their test to provide a certain margin of error to account for the size and thickness of the plant material. It is after all the only variable that changes between their tests.. the size of the plant material cut by the user.

So my thought is, if you could get away with testing just two at a time, that in itself drops the cost of the tests in half, to something that is a little more reasonable for people with a collection of our size.

Also the link above provided by Teresa Koncolor. It has more detail on this. Seems six could be a safe amount as the test was found to be super sensitive.. so they probably already ran these control tests to see how many plants they could fit in a test and be comfortable with the results... that brings the cost of the tests waaay down.