Sawflies and Knockout roses

Be on the lookout.........
It will very soon be time to watch your roses for rose slugs, ( or 'bristly rose slugs'.) By the time you notice the stripped leaves...its too late.

Rose slugs, or Rose Sawflies are the immature stage of a Sawfly wasp. That's right, wasp babies.

Start looking for them on your roses in in late March and early April and prepare to control them into May or June. They are small thin crawler-munchers that resemble a caterpillar, about 1/2 inch long. Find them on the back of the leaf.

But you have Knockout roses.

Yes, Knockout Roses will get sawflies.

"Knockout" roses are not trouble free. It's a myth. I repeat, it's a myth that they are trouble free. Common talk says they are a disease free, trouble free rose. In fact, what they are is a fantastic re-blooming rose that is somewhat resistant to mildews and fungi, which are a common problem for many shrub roses, especially hybrid tea roses. The introductions get better each year...if you want to get new roses every year, that's great!
They do not need pruning; yet they can tolerate a heavy handed pruning session in early spring and mid summer.

However, they are not insect -resistant. Hungry caterpillar-like insects find their early spring leaves very satisfying.

For the last two Springs I've seen the sawfly larva work through dozens of Knockout rose bushes. Your leaves will be munched munched munched. The good thing is the Knockout rose will probably bounce back. It might even be a good idea to prune off the worst stems, since these roses will re-bloom on new wood.


Back to the sawfly. They are numerous in genus/species and they don't look much like the scary wasps that sting you in an old country shed. In fact, the adult sawfly is stingless and serve as pollinators.

(Nice pictures here - http://bugguide.net/node/view/112 )
(Another helpful article overall - http://www.finegardening.com/pages/g00171.asp)

Protecting your rose: I am reading that Bt is not effective, but a Neem oil or horticultural oil will work. ....READ the package directions. READ the directions. Apply as soon as you see the critters, and again every 10 days to two weeks until about Memorial Day or until they disappear.
Oh yeah, and READ and follow the package directions.