Your experience with peach leaf curl resistant Prunus in the U.S

@Oregon_Fruit_Grow and I are interested in your experiences growing PLC-resistant peaches and nectarines available in the U.S. We already have the lists from various university, breeders, and sellers.
Thanks!

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List from US.

Varieties proven to be resistant and widely available
Frost
Oregon Curl Free
Salish Summer

Varieties Claimed to be resistant and widely available
Nanaimo
Betty
Avalon Pride
Indian Free
Black Boy
Muir
Kreibich - Nectarine (10/7)
Pacific Pride - Nectarine (10/7)
Morton - Nectarine (10/7)
Landt (10/7)

Varieties Suspected to be resistant - In general unavailable for purchase.
August Etter
Early Charlotte
Early Redhaven
Early Crawford
Indian Blood Cling
Peregrine
Jay Haven (10/7)

Varieties from outside US
Cesarini - Apparently bred for PLC resistance in Italy.
Bella di Roma - Aliblanca

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Oregon Curlfree had minimal curl for me this spring, its second year in the ground, with zero spraying of any sort. I didn’t methodically count the percentage of leaves showing serious symptoms, but I’d guess low single digits, and it was short-lived in early-mid spring.

I grafted/budded both Indian Free and Salish Summer onto the OCF late this summer, so assuming those take (so far look good) and bud out in spring, I’ll be able to give feedback on them as well. Seattle is nearly a perfect environment to put alleged PLC resistance to the test.

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Those are the only cultivars that this nursery sells minus Early Redhaven.

http://www.greenmantlenursery.com/fruit/peaches.htm

Grandpas Orchard lists Early Redhaven.
https://www.grandpasorchard.com/Tree/Prunus-Early-Redhaven

Indian Blood Cling isnt that hard to find. Dave Wilson Nursery has them at alot of places. (They even list Willis Orchards :crazy_face:)

https://www.wheretobuy.davewilson.com/home-gardens/where-to-buy/retail-sources/Indian%20Blood%20Cling%20Peach/INDBL/product-information/product/indian-blood-cling-peach/1

Also listed in the CVN catalog

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Iowa White is listed under the ‘Current Facts’ as being a White Blood peach…and it is freestone. They go on to say that White Blood peaches are resistant to PLC.

As far as i can tell im the only one on this forum growing Iowa White and my trees are young…so i have nothing to report really.

Miekel is the only one that i can tell other than Ericka that is growing it and he is calling them a landrace at this point…as they seem to be near bulletproof. These could be a strain of or actually the peaches that some folks call Navajo… as they are also freestone.

Ripe mid Sept in La Farge WI

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A microclimate certainly determines disease pressure. In my 2 acre clearing in the middle of an evergreen forest, all of the advertised PLC-resistant peaches I’ve tried have developed more than 75% curl, e.g., Frost, Oregon Curl Free, Betty, HW272, Avalon Pride, Nanaimo, Salish Summer, Charlotte, Indian Free, and Black Boy. With three Kocide/ Lime Sulfur sprays, I could reduce PLC to about 20%.
But if trees make it to 12+ years without being weakened by curl, PLC drops to about 0-1%. I’m at that stage with Avalon Pride. Salish Summer made it to that point but the weakened tree looked bad. It sent up a shoot above the graft so I topped the tree. Now will be interesting to see whether that PLC resistance also occurs in the new shoots of an older tree…or do I have to start over!

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Thanks for the data. Could you please list the age and is the vigor (shoot length growth per year) of these trees that get 75% curl if unsprayed.

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All trees below get PLC except for 15-year-old Avalon Pride and 15-year-old Salish Summer.
After first couple of years of 75% PLC on all of them, I started spraying all of them. So now I have no unsprayed trees. Except for Avalon Pride and Salish Summer, all these sprayed trees still get 20%+ PLC.

Frost - dying at 10 years with PLC and canker, approx. 4" growth/year, removed
Oregon Curl Free - 3 years, approx. 8" growth/year
Betty - 8 years, approx 4" growth/year but lots of blind wood. Looks like on its way out.
HW272 - 2 years, approx 6" growth/year
Avalon Pride - 15 years, approx 12" growth/year. Maybe this is just in a good spot! No longer any curl.
Nanaimo - 10 years, approx 8" growth/year
Salish Summer - 15 years, approx 2" growth/year, topped tree, new shoot left to grow. No PLC on established tree.
Charlotte - dying at 5 years with PLC and canker, approx 4" growth/year
Indian Free - 10 years, approx 10" growth/year, removed because ripened too late
Black Boy - 8 years, approx 10" growth/year, removed because ripened too late

Conclusion: Some now-dead trees with PLC grew very slowly and also were affected by canker. Others with PLC grow at a more moderate rate. The fastest growing tree affected by PLC (Avalon Pride) has now outgrown it.

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From what I have read PLC weakens the tree due to de-foliation, 12"/year is the shoot growth target for mature trees which determines how much nitrogen to supply per year. Do you fertilize/ed these trees? strangely, your Avalon pride is growing at optimum rate.

I think thats why the advice is to spray the resistant varieties for the initial 3-4 years at their peak growing age for them to be able to gradually build up defenses against the fungus.

It should have resistance/tolerance.

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Annual top mulch of horse manure/shavings is sole fertilizer. My trees also suffer from a high water table which probably makes it harder for them to put on 12" growth and outpace PLC.
For high disease pressure areas like mine i.e. high water table with limited air flow, I think applying spray for first 10 years would be advised.
What do you think is the physiological explanation of PLC resistance re: new shoots on an older tree?

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I think it’s mainly due to genetic heritage. Some research done back in 1981 shows varieties with Redhaven lineage showed tolerance to PLC, while those with Redskin lineage very susceptible.

For the varieties currently sold as resistant there isn’t much I can find on how they were bred. Most I think are just lucky finds like Avalon Pride in Issaquah, WA and Betty from WA as well.

I’ve only been able to track Jay Haven’s lineage which has Redhaven in the ancestory.

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Since childhood in the early 1960’s here in southern CA I’ve observed mature peach & nectarine trees on semi-dwarf rootstock put out 4 to 8 feet of shoot growth per year. Notice how R. Martin discusses 70% of the tree on the ground after pruning.

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Look at it kind of in the sense of the trees lifespan. In the beginning you get that 4-8 feet you mentioned. At some point that will really slow down and the growth will be less. Think of that as it’s mid life(most big growers replace their trees then). From that point everything will slowly go downward until it dies. On the subject of curl free. The ones I tried were not exactly curl free and had pretty poor taste. Almost stringy. If you want to play the peach game your going to have to spray for everything in your area.

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I’m accustomed to peach tree orchards whose 70+ years is terminated by residential development, not decline in growth or production. There are peach and nectarine trees in my former neighborhoods in the 40-60 year range that are still going strong.

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Remember I’m on the east coast. Peach trees are short lived disposable trees here. 20 years is a good run. Just about all fruit trees follow that pattern regardless of how long they live.

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@Robert
The decline of pit fruits noticed nationwide is most commonly due to crownrot infected rootstock. Mass production has its pitfalls. Two years ago I personally removed a Mid-Pride Peach for that very reason.

This is true for many of the fruiting plants I grow. Young Citrus is especially difficult. Bananas are spray free!

I’ve grown peach trees for over 45 years in an urban lot close to Vancouver, BC, (in a climate slightly worse than Seattle’s). I only have room for one peach tree, originally Renton (twice), then Frost, currently Redhaven.

Renton and Frost had some curl, but not significant enough to damage the trees; but I didn’t think that they tasted as good as the Redhaven peaches that I could buy. So, in 2021 I planted a Redhaven and hoped for the best. It had some curl the first year and last year, but it could be controlled by removing the damaged leaves. I sprayed the tree with copper last October and again this spring in mid-March. The result: no PLC at all, and better yet, no sign of Coryneum Blight, which has traditionaly been the worst problem affecting my peach trees. I just sprayed it again and hope that next year will be as good for fungus control. I also hope to get a better crop than the four peaches that I got this year.

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Did you spray Redhaven because the infection was worse compared to Frost and Renton?

Never heard of this variety.

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I sprayed Redhaven because it was not advertised as PLC resistant and as a preventive spray for Coryneum Blight, which is still present on an adjacent plum tree.

I guess that Renton is an older variety that was advertised as PLC resistant, but I haven’t seen it for sale in recent years.

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My Indian free, Salish summer amd Charlotte have almost zero plc so far. I have had them for five years or less. Five years for Indian free, two for Charlotte and one for salish summer. A leaf here or there. I do not spray anything here in Portland.

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