Apples cracking due to heavy rains
Recently (the week before last), we got a lot of rain (just under 7" in a 7 day period). Earlier this week I noticed that some of my apples have cracked and started to rot.
At first, I thought it was due to the bags. It seems that when I applied them, I cut off the corners, but didn't puff the bags out. So, while the corner is cut off, since the bag is still closed, there is no water draining through the cut. I started to go through the process of puffing out (separating the plastic) in my ~250 bagged apples. As
I went through the trees, I started to notice a pattern. It seems that almost all the cracked apples were on M27 rootstock.
Of my M27 trees, Hudson's Golden Gem (in ground), Red Boskoop (in ground), and Karmijn De Sonnaville (potted) were all badly cracked (more than half the apples on each tree). The only apples on M27 without any cracking were Akane (which surprised me, as Scott has mentioned that this one gets skin problems) and a potted Ashmead's Kernel (though it may just be a M27 rootstock, as it grew back from the graft union- hopefully I'll know this fall).
While I bagged most apples, I left a few out as backups and I noticed that the one un-bagged apple on those trees also had a large crack (it just hadn't rotted yet).
I have 15 fruiting non-M27 trees on dwarf rootstocks. Of those, there was a total of 1 cracked apple, on Egremont Russet. Has anyone else noticed excess cracking from M27? Is it just the smaller crop load on these trees that encourages cracking (none had more than 8 apples)? Or, maybe those 3 varieties just happen to be most susceptible...