It all depends on what cane borers are a problem where you garden. A well respected rose grower out in California doesn't bother with sealing because his borer's only go down half an inch. In my garden, I've followed a different kind of borer down eight inches. This can be a bad thing on a HT, but tolerable on some Old Garden Roses. What I found was that my borers go into freshly cut pith. When I would prune in late January, the pith would be too tough for the borers who would come out (presumably) in late April. Later pruning in late March would lead to problems. This is one of those times when keeping a garden calender (not a every day of the year, but a multi-year) so you could check when you pruned those Knockouts last year. That would give you more of a feel for when the borers could find success, and when you could interrupt them.

hello Michael: The Ceratina Bee females WILL continue to tunnel into the plant to accommodate multiple rearing cells. They don't stop at just one cell. The general range is two to twelve cells, although many more than that have been observed. At a minimum size of 3 cm. per cell, twelve cells means the females will have excavated well over a foot into the plant. I'm not saying they will go that deep all the time on every rose they nest in, but as you have already discovered, they may certainly go more than just an inch or so down the cane. Please check out the article I provided and the references there. I'm glad that you don't see much Ceratina bee nesting where you are. Baldo lives in California where these bees are also apparently uncommon. However, Ceratina Bees are quite common around here, and they will nest in rose canes if one doesn't seal the cuts. To speak generally, if you don't get the bees where you are, you don't have to seal the cuts. If they are present in your area, it's a very easy preventative. Actually, garden roses aren't even their preferred nesting plants. They much prefer native species - roses and otherwise. So it doesn't take much to convince them to move on and look for better sites elsewhere.- just a blob of glue that disappears in a short time. And Susan - No these aren't leafcutter bees. In fact, they are so tiny that you might not even recognize them as bees at all. To the naked eye. they do look more like gnats They are considered beneficial pollinators, however, which is why I don't recommend insecticides. This post was edited by nickl on Sat, Aug 17, 13 at 13:19

I have a large potted rose garden in Marin co.Ca. above San Francisco.I am a renter and have moved many times.Each time my garden travels w/ me to the new home.Call me CRAZY and some have, but I love flowers and plants and esp. beautiful,fragrent ROSES.Anyway in my last move I noticed an unusual amount of cane dieback in the spring.To make a long story short,after months of cutting back, seeking answers from local nursery men and women,trying various things and products to NO AVAIL,COTINUALLY CUTTING THE DEAD OFF SEEING ONCE HEALTHY,FULL VIGOROUS PLANTS DWINDLE TO NOTHING,DESPERATE I FOUND THE MARIN ROSE SOCIETY AND GOT ONE OF THEIR NICE ROSARIANS TO COME BY.She knew instantanty what it was....CANE BORERS! UGH! She said to cut the canes back and seal the ends and clean off the union buds smooth and that Icould scratch the surface of the union bud with a wire brush to encorage NEW CANE GROWTH and my plants would be as good as new.Finally I had hope.Yesterday I finished a gruelling 2 full days of cutting and sealing 75 rose bushes and trees.MY HANDS WERE A MESS CUT AND PUNCTURED,BUT IT WAS A LABOR OF LOVE! I was losing my plants at the fast rate of cane borers appetite.The infestation was so bad that I did find a very strong product from Bauer called tree and shrub insect control.Its so strong and toxic that you can only use it once a year,but I was desperate.I used it 1 month ago AND TO REALLY KICK SOME BORER-ASS,Im going to spray as soon as the winds die down with a Bondi product made with pyrithrenes,supposedly not too toxic made from chrysanthamums.I hate using chemicals but nothing was working.Well see how it goes...My beautiful Ballerina rose,which lost all but 3 spindally canes and was the 1st rose I treated is full of healthy new leaves and growth.Iam so happy.I also upped their feeding routine and plan on adding alot of rich new soil and nutrients later this year and I will take the kind rosarians advice and try to encouragr lots of new cane growth.Oh p.s. I used clear silicone glue to seal the ends.It doesnt look great,but its waterproof and permenant.Hope my experience helped you.

I'm not sure if this would be of any help, but they also used to hit my raspberry plants. Surprisingly, they didn't show up last year, and I hope the same for this year! I would cut a few inches below those two rings they make on the canes. You don't remove the entire cane. The canes will still grow, so it's not a big deal.