Viruses in the orchard may be spread by dagger nematodes as well as sucking insects. But I think what brought latent viruses (no symptoms other than reduced vigor) to the forefront was some sensitivities of the new Geneva rootstocks to scionwood with latent viruses. This came to light after hundreds of thousands of trees were already planted in orchards when the sensitivities came to light. This seemed to trigger the push to eliminate all latent viruses from any wood being traded or imported.
This has kept us from exporting old Southern apples to places like India, where they would be of great economic benefit. But since most of them have never been virus-indexed, they will never see the light of day there except for a few that managed to be imported and spend two years in screenhouse quarantine.
That is very interesting. If anyone who reads this has noticed a problem of less than expected vigor from any Geneva root stock trees they used for grafting untested scion wood, please follow up with a comment here.
Also, does anyone know if all of Cummin’s varieties are virus indexed? They are the only reliable source of a wide range of Geneva rootstock trees I know of.
I am seeing swelling at the graft union on G41 with around 15% or 20% of cultivars indicating s possible virus. They are otherwise healthy, and vigorous trees.
I assume that testing my 200 apple varieties for viruses and atempting to eleminate them would be cost and time prohibitive. It would be easer to start from scratch.
I found a couple of papers while researching the last couple of days, but they really havent shed any light that hasn’t already been brought up in the conversation. I think the biggest threat is to the commercial orchards that are all hyped about the Geneva root stocks.I can completely understand when you are planting high density and are looking for the highest production levels that any decrease in production is a significant economic hit. My trees arent destined for that kind of market and my typical root stock choices are not the Geneva series ( I see most are reported not to be virus sensitive anyhow). I just planning on giving G935 a 50 tree trial this year.
I think a key reason commercial growers are attracted to the Gstocks is for fireblight resistance. That is probably something to consider in your neck of the woods, especially for more dwarfing rootstocks where it can quickly kill whole trees or whole orchards.
Some trees such as honeycrisp appear virus infected. I purchased my honeycrisp from a reputable orchard so I definitely know they are not any different from other honeycrisp. After a year of suspicion I realized it was due to natural problems with the tree http://articles.extension.org/pages/39083/i-have-a-honeycrisp-apple-tree-that-i-planted-in-my-back-yard-in-south-maplewood-last-year-this-year. Honeycrisp chloroysis will definitely have you concerned the first time you see it Commercial Production of Honeycrisp Apples in Ontario. Never had a virus yet but that’s the kind of thing that is concerning! It could have just as easily been apple mosaic. I’m equally concerned about bacteria as viruses. Let’s face it even bad fungal diseases are something I could do without! Our native wild cherries and plums are hosts to lots of stone fruit diseases. Viruses are out there so limit your scion sources but remember even being as careful as you can be it could happen. Things like cicada spread bacteria or any disease like wild fire. I experienced the 17 year cicada personally and saw it spread fireblight but thank God is was not a virus. 17 year cicada's woke up hungry Late season Fireblight
Exactly, I was using M26 which also had a few compatibility issues, but switched to G41 because of fireblight resistance. The dwarf trees are just for my trellised experiment station of an orchard.
@TurkeyCreekTrees G935 sounds like it might perform okay as a free standing tree but, any dwarf apple should probably be supported and irrigated in drought and I doubt most backyard / Wildlife food plot growers want to do that. It’s good you’re thinking about mitigating the spread of disease and I would be interested to hear what you find about the cost and logistics of virus testing. I have been testing the logistics of a small scale nursery selling fruit trees the last few years. I do not see latent viruses as a significant threat to hobbyist or small commercial customers a small nursery caters to. I’m sure any potential risk is outweighed by the work you do in testing and offering location specific proven performers in a way a large scale operation could not do.
Most nurseries will start their increase block (scionwood trees) from virus-indexed wood such as from the Clean Plant Center of the NW Clean Plant Center Northwest, Prosser, WA and then have the increase block like the Dave Wilson one below tested regularly to be certified virus-free. Most rootstock suppliers do the same thing, and will certify their rootstocks.
However, they only carry common commercial varieties, and if you want a tree of some obscure heritage variety, it will undoubtedly have latent viruses. You may want to have these trees grafted to M111 or M7 or some other rootstock that isn’t bothered by viruses.
I agree. I was looking at the G935 as a potential “tall spindle type tree”. I have found B9 to be insufficient as a dwarf tree here. Doesnt have quite enough vigor to get the job done in my local climate. I know the owners of two local landscape companies that are both interested in doing the selling and me doing the installation of those systems. I also have enough inquires to sell and install the “tall spindle style” here strictly as a backyard addition, but from my own experience in my test plot the B9 trees arent satisfactory for me. M7 actually might work in our climate for the same application. Going to put in a small mixed trellis of those this year as well for test purposes.
Cummins got their varieties, I believe, from the former Cornell breeding program, at least quite a few of their herilooms. I am going to send them a note to find out if they pay any attention to virus issues. I’m not sure what the law is with wholesalers in terms of requirements on the use of virus free stock. I know Adams has a few heirlooms and all their stock is certified virus free. .
Actually I think ACN even mentions on their website that not all varieties they sell are virus free certified. I think all the stone fruit varieties might be.
I would like to see how you are constructing your tall spindle trellis. The trellis ststems I have now are 6’, 3 wire espalier. I will be trying to construct a 11’ tall spindal system made with oil field pipe for posts this spring.
There is no law requiring the use of virus certified stock, either for rootstocks or scionwood. It increases your market however, and many commercial growers insist on it, and thus most wholesalers prefer to deal in certified stock, especially if they ever hope to export. Any imported scionwood coming into the USA must go through virus indexing, malus comes through USDA-APHIS at Beltsville, MD, and then is curated at the Geneva USDA. Thus, the Lady Williams imported from Australia that is at USDA Geneva is assumed to be virus-free.
@alan, I have Dabinett on G.202 that was from Cummins that has a graft union bulge and very sluggish growth. Browns Apple on B.9 about 10ft away and in the same conditions as far as soil and water (wet) and management is many times more vigorous. My thought was always too wet of soil but it doesn’t explain how one tree out of 4 in the wetest part of my yard does poorly and the others are fine.
Here in the northeast I’ve not seen great advantage to using the Cornell rootstocks because fireblight tends to be more of a nuisance than an existential apple issue. I’ve lost a couple pear trees over the years, but not a single apple to FB. The majority of trees in my nursery are on 111 and the majority of my customers have plenty of land- I keep a few trees on 26 if any of them want ornamental espaliers or use pears that can be kept on a small tree no matter the rootstock- such as Harrow Sweet and Asian types.
For customers that don’t fence out deer, vigorous, free standing trees are the ticket. And when you plant one, it is a legacy- one that you can graft anything you want onto.
Assumption is just that. Also I dont see how you can positively be sure the tree is virus free if grown in close proximity to other trees that are NOT verified virus free unless you test it every year before propagation. Which for anyone other than the largest commercial nurseries is not a deal breaker.
Mine are currently 4 wire, with the tallest wire at 10’. 3’ spacing between trees. The height is an issue as well as I would assume it will be for you at 11’, due to our “calm” prairie breezes. Though a site with good wind protection shouldnt be as negatively affected by the wind. I wind strongly recommend vertical supports for those trees until they are established at the final height, I think 1/2" conduit is probably the best choice. I tried a vertical guide wire only and have had too much damage to leading terminals from whipping in the wind.
What kind of posts are you using and were do you get them? I don’t know where to find 14’ or 15’ post locally besides cutting hedge or trying to find old oil field pipe
After I thought about it some more my top wire is at 9’. Mine have been short enough runs thus far (just testing concept) that I used a 4" x 6" x 12’ treated post on each end set 3’ into concrete. Ran all my wires through the posts and then to an in ground auger type anchor. Each line has an in line tensioner to tighten the lines. The next ones I build will only have the top line running to the anchors and the other lines dead ending on the post with a tensioner tied to the post itself and not the anchor. Mine are currently 36’ between posts, 10 tree runs. If I ever decided to make longer runs I would go with those treated landscape type timbers every 20-30’ I suppose between end posts. I used 12 ga wire for my lines and that seems adequate to me at this point.
My impression was G16 was the only Cornell rootstock with serious virus sensitivity issues. I found that out after parking various buds on the trees from Botner wood and I think I killed most of my G16 trees that way. I have about 10% of them left now.
