Please Don't Eat the Roses

While soaking up the sunshine and giving the perennial border a once-over (weeding, deadheading, general inspecting) this weekend, I noticed a pretty serious problem with the White-Out roses there:

Not certain you see see the problem? Compare to this photo taken just two weeks ago:

So where there used to be two big, full, green rose bushes, we now have two crispy brown ones. (Although if I'm being honest, that photo above isn't without some warning signs that I failed to notice. The brown you can see easily are actually pretty harmless dried rose hips from the previous season, but when I zoomed in on my the file in iPhoto, I could see the beginnings of spotting on the good leaves.)

Anyway, here's a closer look at the damage, which is extensive:

The leaves look lacy and brown, crispy and dry. But with all the rain and cool temps we've had this spring, that didn't make much sense. 

Some internet research brought me to the Missouri Botanical Garden, and they have an excellent visual diagnosis of roses page. It was easy to scroll through the photos of various rose problems and pick mine out of the lineup: rose slugs. They also had links directly to lots of great information about each problem and how to solve it. 

When I went out today after work to check the roses for these pests, here's what I found, on the first try:

Three rose slugs on one leaf, sucking out all the good, tender green parts and leaving behind the papery shells of the leaves. 

Not good.

So the thing about these rose slugs (also known as sawflies, a type of primitive, non-stinging wasp) is that they aren't caterpillars, despite looking very suspiciously like a certain voracious one I've read about. The kind we have supposedly have just a single life cycle, which is good news: Once they've grown into sawflies, they'll fly away and new leaves can grow in.

Hopefully it's not too late. The damage to the white roses in the perennial border is pretty bad--not many green leaves left to speak of. I could spray them with an insecticide, but at this point, it seems … pointless. The damage has been done, and if I poison everything, I'll also be harming useful predators like this guy:

While I was taking pictures, this brown paper wasp flew in started munching. From what I have read, paper wasps are the primary predator of rose slugs, so he's pretty useful. Too bad Kirk just knocked down several small wasp nests from the corners of the front porch a couple weekends ago. Maybe it's not a coincidence that it's within these same two weeks that our rosebushes have tanked. Now I know better, and if we get a second chance (for both wasps and roses), maybe we'll let a little wasp's nest or two stand if it's near the flower bed.

Anyway, this last picture of my white roses pretty well sums up the situation:

One crummy flower is open, but has been chewed (which is a little hard to see in the washed-out part of the picture). The leaves to the right show classic rose slug damage, and you can see a greenish-yellow rose slug right on the leaf. 

Of course, once I was done taking pictures, I got to work picking off the bugs and throwing them in a bucket to feed to the chickens. That was easy on the newer, smaller David Austin rose bushes in the cutting garden. They didn't have nearly the same amount of damage, either. So far untouched are the rosa mundi bushes in the vegetable garden, but I will certainly keep an eye on them now.

But the roses in the front … whew. I had to give up trying to pick rose slugs off by hand. The bushes are too big, and there were just too many. I ended up turning the hose onto the jet spray and blasting the leaves from below to try to knock off as many as I could with the water.

And now, for the foreseeable future, I will be on bug-picking patrol each day to try to get them under control before they completely decimate all the roses. Wish me luck!


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