Paul: Did Dr. Lockhart feel that HVX is more/less of a threat today than say two years ago? Was there a trend discussed? Is it getting worse?

Not discussed that I recall. Lockhart presentation was only place hvx was discussed that I attended. I did see two tour gardens with a hvx infected plant - which tells me it's not always obvious even to collectors if they have not seen it before. IMO, even if someone told me it is getting better or worse, it wouldn't change my diligence - it still exists and unless you buy from sources that test and use good practices and demands the same from their suppliers - we risk buying virused plants.

Maybe Chris from Hallson's can weigh in with his observations of how hvx plants in supply chain is changing.

Paul

On the plants getting infected from infected soil... I was unable to attend the keynote, but I understand that not only was this surprising, but even more surprising that one was infected 18 months after the infected plant was removed... and they don't know how long the virus might persist in the soil because the study ended at 18 months...

As to the false negative... I understood that it is possible for the plant not to show positive if it hadn't had enough time to build up sufficient viral load to show up... not sure how long that is supposed to take...

But the threat of false positives came up on this forum not long ago... the concern that a plant might test positive and get thrown away even though it was healthy. I spoke with the Agdia rep about that and he said they can't get false positives to happen unless they do the test incorrectly. The antibodies in the test strip are so specific to HVX that a false positive is as close to impossible as human error can manage.

Very startling that he had no trouble finding plants that showed obvious signs of infection... he just walked out the door of the hotel. I later checked and found obvious color bleeding and tissue collapse on five of 8 hostas I checked in the hotel plantings... I think they were Gold Standards and Paul's Glorys...

He also had a beautiful leaf in a vase on the table that showed not one iota of infection but tested as highly infected. He got it off a very healthy looking plant outside the office park where his office is located.

I'm uploading a video I took of the testing process at the Agdia booth... I'll post the link later...

upload completed... if you'd like to see how easy it is to test a piece of a hosta leaf for HVX, check out this Youtube video...

http://www.youtube.com/watch?v=0JX7d3GeGzY

i cant understand this one:

3 HVX was not spread by contaminated knife during division of hosta crowns. This suggest that spread by this means may be significantly less frequent than by cutting tools.

====>>> isnt a knife a cutting tool??... whats the differentiation?

ken

ps:

In addition I spoke with the rep for the HVX test strips - and came away believing a properly tested HVX infected plant can not show up negative for HVX

====>>>> you really didnt expect him to agree that his product has a failure rate????

I hope Paul can clarify what he meant on number 3... I didn't get that either.

Before I respond to the other point, let me say that I agree with Ken's primary response to HVX in hostas and testing - it doesn't make much sense to test an inexpensive hosta with a strip that costs almost $6. If it looks virused, it probably is... toss it.

But the latest info - that the virus can persist in the soil for 18 months and we don't know how much longer - that opens up a new possible reason for wanting to test. I think if I have to remove a plant, I'll probably replace it with something non-hosta and avoid the issue altogether - but I can see someone wanting to know for sure if they are dealing with HVX out of concern for the soil in that section of their garden. Many folks are dealing with limited space.

I think the false positive question is important, because I think people are pretty OK with disposing of diseased plants, but the idea that the strips might tell them to throw away healthy plants might motivate people to not test - after all, if you can't trust the test, why bother?

So as the false positives... like Ken, I'm more skeptical than most... but the science of the strips suggests false positive are almost impossible IF the testing strip is correctly used.

Two facts support that.

First, the results of the strips match extremely well with Elisa testing.

(from wikipedia..."Enzyme-linked immunosorbent assay (ELISA), also known as an enzyme immunoassay (EIA), is a biochemical technique used mainly in immunology to detect the presence of an antibody or an antigen in a sample.")

The strips were designed to be the field equivalent of the typical Elisa test done in a laboratory - though in a lab, they are likely to do a whole panel of antibodies, not just a specific one. They use antibodies in a similar way to the Elisa testing. Short of an electron microscope, this is the standard set for testing for virus. In fact, it is the standard screening tool for human diseases like HIV and West Nile.

In both kinds of testing, false NEGATIVES will occur (plant testing healthy even though it has the virus.) This is most likely due to the plant not having built up enough "viral load" to show up in testing. I don't know how long a period this can be... my impression is that the virus spreads throughout the plant fairly rapidly... but I believe Dr. Lockhart has had the experience of testing a plant negative and then having it test positive later... so not many false negatives, but there will apparently be some.

Second, the antibodies on the test strip are quite specific to HVX. Agdia markets a line of strips, each designed to test for one specific virus. Once the chemicals mix with the plant juices and mark the virus, that is, for all practical purposes, the only thing that can make those antibodies react to give a positive reading. The "positive" band on the strip is designed to react ONLY with HVX.

The rep says they've tried - and they can't get false positives unless they do something mechanically wrong.

Certainly, nothing is perfect... and the science of HVX is changing as we acquire knowledge... and I wouldn't assume that a negative test guarantees my plant doesn't have HVX... but I think if I got a positive test, I would approach it as a sure thing and destroy the plant.

This sales rep was a pretty interesting kid. He seemed to be more interested in the science than the sales. He didn't hand out any literature... I had to take it myself. He talked about his visits to the ports of entry where the European import plants are checked... and his work with the inspectors to get them away from just checking samples from each shipment to checking shipments by cultivar - the inspectors didn't realize that the way hostas are harvested and processes, the infection is more likely to be spread among the plants in one cultivar than being spread in the shipping container among the plants. Easy enough error to make - our usual model for virus spread is person-to-person...

Anyway, all he wanted to talk about was the virus and what we know so far and the science of the strips - I had to ask him about the pricing...

Point 3 regarding tools and spread of hvx was directly from a slide (as they all were) and wasn't discussed nor questions asked - I can only speculate sawing vs cutting - but IDK. It was on Dr Lockhart's list for possible future areas to examine. AHS gave go ahead for next phase of research and are looking for donations to fund ($20K) - One of the societies pledge $2k on the spot.

Paul

In both kinds of testing, false NEGATIVES will occur (plant testing healthy even though it has the virus.)

===>>> wouldnt a false negative.. be a diseased plant testing healthy .... see immediately below ...

also.. there are 2 or 3 OTHER virus that affect hosta ... that are in no way tested by these test...

discussed with zillis in my yard last convention.. and he suggested the plant had tobacco mosaic?? virus.. rather than hvx ... there goes 6 bucks down the drain ...

ken

rbfranklin... I don't know if HVX is getting worse, but I did happen upon this study that suggests it is getting worse, at least in terms of what we are importing from Holland. They instituted a program based on visually checking plants and an allowable percentage of virused stock - clearly not sufficient as there are so many that don't show before digging and the possibility for cross contamination if you allow even one in 20 to show the virus...

http://www.npdn.org/webfm_send/1074

Ken - I think our two definitions of false negatives are the same???

As to your six bucks down the drain... I guess you got some good information out of it - you know you aren't dealing with HVX on that plant. HVX is different from, I think, all the other viruses affecting hostas in that it is only spread mechanically. The others are, unfortunately, spread by insects or slugs or whatever and many of them are hosted by many species of plants... thus quite hard to control their spread.

So what did you decide to do about the virused plant?

For a not too bad summary of the many, many things that could go wrong with your hostas...

http://www.extension.iastate.edu/Publications/sul14.pdf