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!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.
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.