Did you check for spider mites?

Magpie, that looks just like the spontaneous dieback that affected my Heaven on Earth rose many years ago. It was in the summer and continued until the rose went dormant. The next spring, it started up again, and I removed the rose. I was done dealing with it, and I've never had a rose affected that way again. The cane (s) looked healthy until they started dying back. No spots or cane canker. No cane borers. Very weird. i hope you solve this mystery fast. Diane

So I searched for spider mites (found none) but found a spot lower down the cane that looked weird, kind of like a small split in the cane? I didn't take photos. But there was definitely an area that was a *little* bit swollen and had what looked like an old wound on it, just above that healthy sprout I mentioned. Anyways I cut the cane just below the wound and the pith of the cane was dark brown right where the wound started, but creamy white below. I guess it was doomed. Hopefully the rest of the plant stays okay.

Your John Cabot should survive very nicely, and fill in in no time.

Moses

I hope so, thank you for your input! I guess I learned something new about John Cabot (and other rugosa/hybrids) today, and I'll be on the lookout for it in the future. I do love this rose so I'm so glad to learn the plant will be fine, plus it's so vigorous it will regain that cane and some extra next year.

That's right. JC's flower is very pretty, and the bush is robust.

Moses

Thank you Moses for solving the mystery. I didn't know Rugosas were susceptible to cane girdler before. Last year my Linda Campbell had two main canes withered and died quickly, but the rest canes looked healthy. I don't know what happened so had to cut them off from the crown. Luckily LC is very vigorous and kept growing new canes. It's looking great this year. (Except for the BS in our wet spring).

This photo was taken today.

The Rose Forum’s slot for Plant Pathologist has been open for some time. I nominate Moses.

I found another area that looks just the same as far as the weird spot on the cane, although for now the foliage isn't all wilted. Is this cane also eventually going to die? I love my John Cabot and the idea of losing the 2nd year canes each year is distressing .

@Moses, Pitt PA, cold W & warm/humid S z6

Oh dear, Magpie.

I'm not qualified to answer...but it doesn't look good.

Rugosas and their hybrids are so robust, they almost always shrug off cane girdler. Only a very young bush, afflicted with multiple major girdles all at once could be killed, but the chances of this happening are remote.

You just prune below the girdle. That's all you can do. There is no insecticidal means to kill the larva. It's well protected in the cane, and besides, spray anything: liquid foliar feed, insecticide or fungicide on a rugosa or its hybrids' foliage, especially hybrids that show very rugose foliage, and the foliage will turn tan and fall off. Rugosa family roses have very sensitive foliage that cannot take any chemical spraying, period.

BTW, My favorite 3 hybrid rugosas are: 1) Roseraie de l'Hay, 2) Snow Carpet, aka. Schneekoppe (Gr.), and Henry Hudson. I could make a spectacular hybrid rugosa bed with just these three. RdlH in the back, Snow Carpet in front of RdlH, and Henry Hudson in front of Snow Carpet.

Moses

Rifis,

Plant Pathologist is far above my knowledge level. If you knew how much I don't know you would nominate me for Last Choice Hole Digger, and I still would lose!

Moses

Moses, considering the amount of things there are to know about this world and beyond it, none of us really know much of anything at all, and understand even less.