I top worked a big apple tree and notice at least a couple of the varieties grafted to it had splotchy yellow leaves this summer. It makes me think that they have Apple Mosaic Virus.
My understanding from what I’ve gleaned in my web searching is that this virus is only transmitted via grafting, not air, not insects, not pruning with contaminated tools.
It was surprising to me, that if true, such a virus could survive to continue as a pest. But perhaps its that so many varieties tolerate it fine that it isn’t enough of a nuisance to justify a big enough response to stamp it out. I’m interested to see how those varieties perform compared to what used to be on the tree.
I pruned off Bramley’s Seedling, Golden Russet, Miss Jessamine, Hudson’s Golden Gem and Kandil Sinap in order to graft low enough for my purposes. I don’t recall seeing the yellow mosaic on those. I’m not sure if the host tree was infected, or one of the new varieties.
i do the same. only takes about 10 sec. i keep a corona sharpening steel and draw it 2xs lightly on both sides. just enough to give a small bur. cuts like new. i also dip my wax ends sealed scions into diluted peroxide so i dont transmit anything that might have came from another nursey. maybe overkill but ive got some pests and diseases that have shown up that were never originally present here. pretty sure they came from something brought in.
If I read this correctly, and it is AMV, sounds like I introduced the virus with one of the new cultivars, because I had a couple of the varieties that Skillcult identified as susceptible, that I believe did not exhibit symptoms over several years:
I suspect risk from lack of sanitizing actually might be more meaningful when there’s high “mix.”
For someone like me, I get rootstock from various places, and get scionwood from many people across many more sources through exchanges. Given the larger potential for any one of those sources to have a virus, I could easily transfer something to clean stock across a number of plants unknowingly. The impact of that is probably not huge since it’s just my backyard for the most part but just speaking to the probability.
That said, I do it when I remember but am not a business with specific controls in place…
Regarding disinfecting tools, I’d read something like this before, and this is one of the first hits on a search. I found it pretty discouraging of my efforts at sanitation. The thing I’ve tended to overlook is contact time, and they seem to recommend a soak, rather than just a spray and wipe.
I carry Isopropyl alcohol in a spray bottle almost all the time. If it isn’t fully effective at killing stuff on contact, its still quite good for cleaning.
One of the things that seems important to me is that when spraying my tools with isopropyl between different cultivars, it is not just sanitizing, but also preventing build up of sap on the tools. Since sap can carry viruses, limiting build up of sap has the benefit of physically reducing the quantity of material available to transmit viruses through contact regardless of whether the sanitizing method actually is able to kill 100% of whatever pathogens it comes into contact with.
In my opinion, sanitizing tools does not have to be proven 100% effective to be worthwhile. The point of such practices is to reduce risk of spread. We still benefit even if we don’t achieve 100% success.
I get that. For me the risk is greater. I don’t introduce any new varieties from unknown sources, unless I absolutely can’t get the cultivar from anywhere else.
Probably in the last decade, I’ve introduced maybe 3 or 4 different peach varieties from what I call unknown sources. As I recall the varieties came from Scott Smith or Bob Vance.
I hear about that, but have never really seen that with my tools. I use a modified Zenport grafting tool for grafts and never clean it. I don’t see any buildup on it. Maybe it’s the tool?
For fall budding, I use a short blade knife. But again, I don’t experience any buildup on it. I don’t have it handy to take a pic of it. But I don’t recall ever seeing sap on the blade. I’m talking T-buds here.
I’m not just referring to a grafting knife. I’m referring to pruners too. My pruners used to get really gunked up years ago before I learned to keep isopropyl on hand in a spray bottle.
A good spray of 91% rubbing alcohol on both sides of a tiny grafting knife sanitizes it rapidly and effectively. Isopropyl alcohol - Wikipedia
The University of Arizona article stated
‘They also recommend leaving them to soak for 2 to 5 minutes between pruning trees or plants where signs of infection have been identified.’ This tool soak is for cases where infection has been identified, like when pruning fireblight out of a pear.
When referencing Isopropyl alcohol as well as bleach for sanitizing horticultural tools, the author said ‘All were shown to be effective’
Obviously hand sanitizer is also only on your hands a few seconds, but apparently works.
Nothing prevents 100% of unintended infections in plants, but hygienic practices lower the rates that they occur, which is good practice for any nursery or grower. Obviously we want them to work.
Yes, I agree, like with soap and water, cleaning by physically removing the junk is part of sanitation.
The things I spray most with the alcohol are the pruners and my hands probably in that order, then maybe my grafting knife and sometimes scions or the tree if its dirty.
I have grafted from old trees for years and a few years ago the mosaic virus showed up on a couple of the trees in my orchard. The last two years it hasn’t shown itself and when it did the damage was only cosmetic to the leaves. I have been warned of using non-virus indexed graft wood, but will continue to ignore such warnings as long as the consequences remain minimal.
However, I won’t distribute wood from trees that have shown the disease. Only two of mine have.
I never bother with sanitation… even when cutting out black knot. It really doesn’t seem to matter “outside the laboratory”. I also have tons of pruning brush on the edges of my property. I think it helps keep my water table higher for my well- but that’s just a hunch.
Massive amounts of brush from pruning all the orchards I manage. I’m doing that about 7 months of the year and at many sites there are no brush piles, even when customers have many acres.
It is often recommended that one dispose of such brush far away from the fruit trees they were pruned from for sanitation reasons.
I commend that level of detail and precautions trying to keep things as sanitary as possible.
My wife now works in a hospital setting where sanitization is important; It’s my understanding that at least 20 seconds helps to eliminate pathogens fully if the sterilization method is effective. I’m not sure how transferable that concept is to plant pathogens, but in the data you discussed that @murky shared it seems a longer period of time is even more effective.
That said, we are currently struggling through a digestive virus and just this evening she brought up the point that isopropyl alcohol is not effective at killing neuro virus but that bleach is effective (which we have been cleaning regularly with).
I’ve read posts from @scottfsmith indicating the blowtorch as an effective method for black knot; I would recommend avoiding it on any grafting knife that is made from hardened steel like my Tina. They are tempered to remain sharp longer. I’m not sure how long it takes to remove temper (300F +?) or how that compares for effective sterilization (time or temperature based).
The recommendation at the bottom for Lysol is the kind of information I think we all could use for better results regardless of the species/pathogen.