Summer rots are a problem for apples in areas of hot, humid summers. The problem gets worse the farther South you go. Here are some links that will help you identify various summer rots and a short list of apples with their resistance rating against summer rot.
Here is a first crack at my own experiences. The only rating that seems off on the Hanson list is GoldRush, it is not susceptible at all for me. It can get some minor spotting but it doesn’t affect the fruit so I don’t really care about that.
I also added ratings for watercore and mealiness as these are also reasons to rule out apple varieties in hot climates.
Key
VR= very resistant
R = resistant
MR = moderately resistant
MS = moderately susceptible
S = susceptible
HS = highly susceptible
MW = moderate watercore issues
HW = big watercore issues
MM = moderate mealiness problems
HM = big mealiness problems
Wiliams Pride - VR; HW Monark - VR? Early Joe - MR State Fair - MR Pristine - VR Jefferis - S; HM Fall Pippin - R Worcester Pearmain - S Ginger Gold - MS Akane - HS Young America - MR Cherryville Black - VR; MM Laxton’s Fortune - MR Golden Nugget - VR; MW Holstein - S; HW Gravenstein - MR Pitmaston Pineapple - VR Zestar! - S Pixie Crunch - R Kentucky Limbertwig - VR Sierra Beauty - MS; HW Tumanga - R Ribston Pippin - HS Kidds Orange Red - R Gala - MR Freyburg - MS Calville Blanc d’Hiver - HS Black Gilliflower - S Allington Pippin - S; HW Swayzie - R Egremont Russet - HS Blenheim Orange - VR; MM Shizuka - R; MM Smokehouse - MS Hewes aka Virginia Crab - MS Wagener - S Adam’s Perrmain - MS Orleans Reinette - MS Waltana - MS; MM D’Arcy Spice - HM Cox’s Orange Pippin - MS; HW Court Pendu Plat - MS Hooples Antique Gold - MR Razor Russet - MS Rubinette - MR Oliver - R Canada Reinette - S Hawaii - R Hunge - R; MW Old Nonpareil - MR Pomme Gris - R Claygate Pearmain - HS, HM, HW Lamb Abbey Pearmain - R Lady Sweet - MS Roxbury Russet - MR Reine des Reinettes - R Swiss Orange - S Westfield Seek No Further - R Hubbardston Nonesuch - MR Enterprise - R Spigold - MS Apricot - VR Grimes Golden - MR Maigold - VR Hudsons Golden Gem - HS, HW Wickson - MS, MW Bonne Hotture - R Suncrisp - VR Myers Royal Limbertwig - MR Mother - MS Mutsu - MR King David - R Reinette Clochard - MR Ashmead’s Kernel - R Jonathan - R Fuji - MR Abbondanza - R Steele’s Red - R Winesap - R Rambour d 'Hiver - VR Harrison - R Golden Russet - S American Golden Russet aka Bullock - S GoldRush - R Katherine - MR Newtown Pippin - MS Black Limbertwig - VR Rusty Coat - R Black Twig - VR White Winter Pearmain - R Pink Lady - R Campfield - VR Gilpin - VR Yates - VR ALL European Cider Apples - HS. I grew out over 25 varieties and they were all horrible rotters and many had horrible watercore issues. Also horrible with fireblight. Overall a real nightmare!
I’ll switch Enterprise to R, I mistakenly thought Hanson had a VR on it and I didn’t fruit it enough to give it a VR. But it never had any rots for me so maybe it would be VR if I had kept it longer. It was a supremely boring apple with rubbery skin so it didn’t last long.
Thank you for the list. I only grow a few of those varieties but in my area most apples with a Golden Delicious parent are very susceptible to Bitter Rot. I have also noticed that apples that mature early are less effected than the fall apples that sit on the tree a long time.
I guess it makes sense that I have had trouble with BR on both Pink Lady and Goldrush. Never had any BR on Winesap.
Perhaps you could make a list too? I think having more lists and more apples on the lists would be really helpful since Summer rots are often overlooked in official sources.
And knowing the specific rot a cultivar of apple has problems with would be useful too. That way if you know White rot is a problem for you and Bitter rot isn’t you still can select an apple that susceptible to Bitter rot as long as it has some resistance to white rot.
That is one reason I stay away from ( as much as I can) any apple this has Golden Delicious in the gene pool. I do have some dwarf Golden Delicious trees in my orchard but only there because it is a good pollinator. I bought them from Stark Bros for $10 each on sale.
There was a very interesting article I read some years back, while I was researching different apple varieties, about the apple breeding programs. All the problems that are encountered with breeding and inbreeding using the same few apples in the entire breeding linage. If you have the same apple in the genetic linage over and over again and there are problems with that apple it just makes that problem worse. It was eye opening and changed my mind about a lot of apples I had been looking at and I have gone in an entirely different direction with my apple tree choices.
It can be really hard to distinguish between Bitter Rot and White (Bot) Rot with certainty. Pictures of Bitter Rot normally show a series of concentric rings and a “V” lesion when you slice the apple in half but its hard to know for sure, especially when the infection is just getting started. When the apple pathologist diagnosed my problems many of the apples had both.
We had two terrible years of Bitter Rot in a row which forced me to reconsider growing apples. I thought I was prepared after I raked all of the previous years drops, leaves and prunings to the center of the rows and flail mowed them then bought several of the modern (expensive) fungicides and tightened up on my spray schedule but I got hit anyway.
After these experiences I concluded that the weather in my area can produce terrible years for Apple rots just like it does for fireblight and there is not much that can be done about it unless you are willing to spend lots of money and time spraying the apples every 5-7 days which would be a LOT of sprays. Don’t have those problems with the other fruits we grow so we pushed growing apples to the bottom of the list.
EDIT: Several new pathogens were identified that can cause Bitter Rot in some years and it looks like the researchers expect the problem may get worse
I have been following the posts you make on your orchard. It sounds like it’s a tough area to grow apples. Perhaps try some of the old apples of the South or look at modern apples that resist Summer rots and put them in a test plot?
I also find diagnosing Summer rots to be challenging. Last year I had 50% of my Enterprise apples had some kind of Summer rot. I thought it might be bitter rot but the fruits never developed the characteristic v-shaped lesions. Instead it was mainly a surface problem with most spots less than a 1/16 inch deep with a few a 1/8 of inch deep. I hope this year it will not appear or at least that I can identify it.
I understand your frustration with BR. Its common to start with a few specs on the surface that turn into major rot areas over time. We spoke to one grower in Virginia where his apples looked good when they went into cold storage but were full of rot just a month or two later. So bad he could not make cider with them
My area really is lousy for Apple growing but improves drastically 100 miles to the north or 100 miles to the west. We have identified one apple variety we can grow like you suggested and grafted 100 to be planted next fall. Put them all on G41 which grows like a weed here. The old trees managed to produce a sellable crop with no insecticides or fungicides. Some people drove a long way to pick apples with no chemicals and they were willing to ignore the sooty blotch and fly spec. Old Fashion Winesap is not a great tasting apple but seems to tolerate my climate and improves in storage. Hope to test Arkansas Black and Limbertwig in the future.
Bitter Rot is a hard nut to crack. It looks like the pathogens that produce Bitter Rot in the Northeast and Midwest are different from the ones that produce the rot in the Mid Atlantic and South East areas. Also, I read about a completely different fungus produces BR in the dry apple growing areas.
Lots of money devoted to research to better understand the BR problem all over the country but I don’t expect any major breakthrough. Perhaps more effective chemicals and more spray.
Here is an interesting article on some of the research done on BR on NC that discusses the northern and the southern versions of BR.
"In terms of cultivar susceptibility, Honeycrisp, Fuji and Granny Smith are highly vulnerable to the northern form of bitter rot, but if conditions are right, “pretty much every cultivar is a target,” Villani said.
The southern/Glomerella form is most damaging to cultivars of Golden parentage, such as Golden Delicious, Gala, Pink Lady, and Jonagold, as well as Granny Smith."
Do all apple rots show up on the fruit’s surface? I could swear my Boskoop has rot that I only discover when cutting into it. Half the crop had internal rot in a dry year. Most bagged, so not insect-caused rot.
If rot tends to be a perennial problem in a certain variety, maybe I’ll cut my losses early and graft-over.
Belle de Boskoop had lots of both watercore and internal rot.
Every time I thought it was internal I found a worm opening somewhere. So I’ve never seen it. But on pears it happens all the time so it certainly could happen on apples.
Back on the original topic, I bought some new rot sprays for next summer. I had way too much rot this summer. I got Merivon and Luna Sensation. I can also put them into my general disease spray rotation as they work on many things. These two are the same class and are very similar but I like mixing it up as much as possible… I think that approach helped me basically eliminate brown rot on stone fruits.
Just found a Plantura site that says Belle de Boskoop is susceptible to core rot. Has anyone heard of that? It perfectly describes what I find in half my BdB crop: large sections of rot, interior only, no exterior sign of anything wrong. And I bag most of my apples but doesn’t prevent this rot. Sounds like a genetic flaw of BdB. If so, am grafting over. I searched high and low researching BdB before grafting and this “core rot” never came up. Shoot. Oh well.