Polareis has a problem - borers?

sunnysideuphill(5)November 4, 2011

After raving about this rose being so bulletproof - early this fall some of the canes went all brownleafed. Inspecting it against the backdrop of all the snow we had this weekend, it is clear on some of the canes that there is a swelling below the dead leaves. I think this is rose cane borer, which devastated my rugosa hybrids 11 years ago.

I know that I should cut off the damaged canes, very low, and dispose of them at the local landfill, not my compost heap. They are almost all huge thumb thick canes, which seems surprising, but would explain why they didn't all "flag" down, which would have been the giveaway to me, having seen that before.

Does anyone know anything about the origin/life cycle of these things? 11 years ago I used a knife to split open a few of the affected canes, and could see the grub inside. But I caught them very early - still late summer.

Have they already emerged, to do more damage next year? These big tough canes may be hard to split open, but I will try.

Heading out tomorrow afternoon to deal with this, will appreciate any insight you can share!

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michaelg(7a NC Mts)

The correct common name of this pest is Rose Stem Girdler.

It is said that the larvae overwinter in the canes before dropping to the ground to pupate in spring. Therefore if you cut off the dead parts below the swellings right now, you will cut down on the number of egg-laying females for next season.

    Bookmark   November 4, 2011 at 4:34PM
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Good Grief! I went at it today with pruners, went back for the long handled loppers, and then went back for the bow saw. One of the original (12 years ago?) canes looked like an arthritic finger (I know because I have a few) - only it was nearly 2" in diameter. Every single branching cane from that original also had knobs. By the time I was done, I had filled the Toyota short bed to a height of 3 feet over the sides - had to do the tarp & bungee trick to get it to the landfill.
And when I got back - yup, I saw a few I had missed.
What's the worst that can happen? I'll have to get a new rose! But I love this one, and hope she bounces back.

    Bookmark   November 5, 2011 at 9:51PM
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Sunny, I just bought Ritausma/Polareis as a band from Vintage. It sure has a beautiful bloom, and I hope I love mine like you obviously love yours.

I do hope she survives the pruning and borers and comes back for another spring and summer show for you.

That was a lot of pruning you did!

    Bookmark   November 5, 2011 at 10:26PM
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rootman(zone 5/6 W.PA)

Dear SSUH,

I've been thinking about your dilemma since reading about it some days ago. I may be able to shed some light on the matter.

In my early rose years I was smitten with the idea of no spray, minimum effort roses and gravitated to the hybrid rugosas. The Susan Verrier book, ROSA RUGOSA, on hybrid rugosas was my Bible. At that time I experimented with almost every suitable variety I could get...over 20 varieties if I stopped to count them. Very soon I discovered, to my great disappointment that the hybrid rugosas as a group are probably the most susceptible roses to the cane girdler.

Here are some observations I made:

The taller bushes such as: Roseraie de l'Hay (my personal favorite), Sarah Van Fleet, and Sir Thomas Lipton drew far more attacks, probably due to their thicker, longer canes...bigger target for mamma girdler and a more secure home for baby girdler than short thinner canes.

Shorter varieties like: Henry Hudson, Fau Darmar Hartopp, and Schneekoppe (Snow Pavement), seemed to go undamaged.

There is no effective spray for stem girdler that I am aware of, and even if there was, the reason for growing hybrid rugosas, for their no spray nature, would be defeated, and besides, this class of roses is so chemical sensitive that a complete defoliation would probably result from the first spray.

Canes that are not outright killed by stem girdler are weakened considerably resulting in poor growth and few flowers.

My Martin Frobishers were the worst for cane girdler. Those nasty 'swollen joints' were everywhere to be seen on them. The bushes consequently never really were able to take off and flourish.

In my selection of hybrid rugosas then (about 20 yrs. ago), I tried to get everything in one bush in the varieties I chose: winter hardiness in zone 5-6 (W. PA), disease and insect resistance, extreme fragrance, large flowers, very double dense blooms (stayed away from the flatter, low petal count varieties) and quick, repeat blooming.

I did not continue my 'love affair' with the hybrid rugosas...moving on to other no spray roses from both old and new classes.

Polareis was a newcomer then and being a big boy I felt he would be chief on the stem girdler hit list. I see I was right. It does make the kind of flower I really like, unlike most hybrid rugosas with their blousy, confused, sparsely petaled, sloppy blooms.

BTW, where I live in W.PA, rose midge fly, Gypsy moth, black spot, downy mildew, powdery mildew, rose rosette disease, crown gall, stem borer,stem girdler, cutter bees, thrips, Japanese beetle, and now stink bug, are rampant. Aphids and spider mites although in abundance here too, are the least of a rose growers problems as compared to the first list of maladies. Did I neglect to mention rabbits and deer, who for me, being a city dweller, are not the nightmare the suburbanites and country rose growers experience.

In my current rose bed of: Buck roses, a very few carefully chosen OGR's, the only surviving hybrid rugosas I grow are: Henry Hudson (a shortie with although flat and small, under 3 inch blooms, they are beautifully formed and abundantly provided), Snow Pavement (Schneekoppe), for its cupped, well formed blooms of such a beautiful, light shade of lavender, and short stature,3 1/2 ft. at most, and Apart...this one may get shovelpruned. Not too happy about the flower form and dead common, pinky/mauve color.

All the other hybrid rugosas are history.

In conclusion, can your Polareises survive the degree of stem girdler damage they are experiencing and give a satisfactory display of blooms and growth even though are not thriving to their maximum? Their vigor may make up for the damage to the point that future stem girdling will be considered part of the deal in growing Plareis. You are the best judge of this.

In the mean time you may consider trying some of the shorter hybrid rugosas that appeal to you as a trial run. They may prove to be very resistant to girdler or even virtually immune.

I am sorry for your problem, but growing roses is not easy, unless you are satisfied with the Knockout line, which to me are 'heartless creatures', a good 'devil strip' rose, and nothing more, but that's just one man's opinion.


    Bookmark   November 10, 2011 at 5:28PM
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Thanks, Rootman - and your observation that the bigger ones seem to be the targets is supported by the ones I had that succumbed all those years ago. I have two Therese Bugnet bushes, bought one about twenty years ago, it survived that onslaught, although I pruned it down to 10". It bounced back and even sent out two "daughters" - one I gave to a friend, the other I kept, and the two of them are about 5' tall and very healthy. But TB isn't really a typical rugosa hybrid, either, I don't think.
The Hansa (?) from my grandfather's farm, ca 1920 has survived, as well as a patch of Apart on a neglected hillside. And a Linda Campbell. But those are the only ones I had left, until I bought this Polareis.
I too hope it bounces back, but I have to say that I am very taken with my gallicas and my huge old Alba which don't seem to be as susceptible.
Roses are certainly a life long learning curve!

    Bookmark   November 12, 2011 at 3:52PM
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Below is a link to a report about some observations of roses & insects at the MN Landscape Arboretum. Has some pictures to help ID the problems---they also make the observation that the stem borer problem was mainly on the Hyb. Rugosas. My own experiences have been that Hyb, Rugosa are a favorite of Mossy Rose Galls.

Here is a link that might be useful: U of MN Ext. insect info

    Bookmark   November 13, 2011 at 1:28PM
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I bought several Hybrid Rugosas, looking for roses appropriate for one 5a. So far they are in their first year, and not blooming very much. I am thinking they need more care than I had realized. Maybe they are not plant and forget roses.

If I want to inspect for cane borers, what should I be looking for? The pix an the site above aren't telling me very much.

    Bookmark   November 14, 2011 at 10:01AM
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michaelg(7a NC Mts)

Nastarana, with the Rose Stem Girdler, you will see a medium to large area of wilting or dying foliage, all the stems coming off a larger cane above a certain point. At this point there will be a swelling of the large stem, which may be subtle or obvious. Underneath the bark in the swollen area are small spiral tunnels. I don't know why the UMN page calls it "rose stem borer," they should know the correct name.

Here is a link that might be useful: more links

    Bookmark   November 14, 2011 at 11:12AM
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Hi Nastarana,

Don't give up on your Rugosas. They are roses with a good survival instinct, that's all, which means they get off to a slow start when newly planted in the garden. This year they are probably just growing roots. Expect to see more growth and improved bloom with every passing year. They don't need a lot of care compared to other reblooming roses, but many of them do appreciate a little extra water in dry spells to keep them at their best. As the subject of this thread indicates, Rugosas are also sometimes singled out for attack by some weird bugs. I guess it's the price we have to pay for these healthy, hardy, fragrant, reblooming, easy-care roses. (Can you tell I love Rugosas?)
Stem girdlers are a larva that eats around the wood under the bark and causes a swelling like a knuckle in the cane. The cane will snap off easily at such a "knuckle" and you can see where the larva has been eating its way around--sometimes you can find the larva itself. Leaves above the knuckle will die off. Usually the plant sends out new shoots from below the knuckle. You can control stem girdlers by cutting off the canes below the knuckle and throwing them in the trash or burning them if that is permitted in your area--don't compost because that does not get rid of them!
Stem borers attack any rose, not just Rugosas (in my garden at least). They go for freshly cut canes and drill a hole right down the middle--it even looks like a tiny drill bit was used. Then they lay their eggs in the hole that hatch out and cause minor dieback. You can control this by putting a dot of Elmer's glue on the cut end of each cane as you prune.

    Bookmark   November 15, 2011 at 1:17AM
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michaelg(7a NC Mts)

mille fleurs offers a lot of great information, but she or he is wrong about how the eggs are laid. The science-based sites that I linked above will tell you the eggs are laid on the bark of lower canes, not in cut cane ends. The insects that drill in cut cane ends are small predatory wasps and the small carpenter bee. These do far less damage that the stem girdler and certain other borers. I have plenty of these twig-nesting bees and wasps and I don't worry about them.

    Bookmark   November 15, 2011 at 10:00AM
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I am not giving up, Mille fleurs, if only because I spent too much money and time already on them. I do wish Martin Frobisher would bloom, he looks so lovely in photos.

    Bookmark   November 15, 2011 at 9:52PM
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rootman(zone 5/6 W.PA)

Nastarana, please have patience with your new hyb. rugosas.
What is often stated about own root roses that are under a year old when purchased (which yours may well be), is: "The first year they sleep, the next year they creep, and the third year they leap."

Also, although many hybrid rugosas repeat bloom very reliably, even the first spring flush is not as lavish as a number of other roses. I can think of several other classes of roses whose flushes of bloom are more abundant. The reliability, winter hardiness, relative disease and insect resistance, fragrance, and adaptability are their strong points.

I think there has been some confusion about the distinction between stem borers and stem girdlers.

Stem/cane borers attack the cut ends of canes and bore holes whose openings can plainly be seen at the cut end.
Stem/cane girdlers attack the sides of canes causing
what looks like swelling of the damaged stem with normal looking stem above and below the swelling.

    Bookmark   November 16, 2011 at 2:29PM
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I stand corrected, MichaelG. I know I have found little larvae both in the swollen knuckles created by cane girdlers and in the drill holes in the end of canes created by stem borers, but could not tell you much on an entomological level about their life cycle. I agree that cane girdlers are far worse in the amount of damage they do.

In any case, all the best to you and your Rugosas, Nastarana! Post some pictures in a year or two when they have come into their own.

    Bookmark   November 17, 2011 at 11:00PM
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michaelg(7a NC Mts)

mille fleurs, an important difference is that the bees and wasps that drill in cut cane ends do not feed on rose tissue. They just make a nursery chamber for their larvae and feed them with pollen or aphids, so the damage is limited. But the stem girdler larvae, the larvae of rose stem sawfly, and other borers feed on the rose stems, grow larger, and move around inside the plant.

    Bookmark   November 18, 2011 at 3:00PM
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