This may seem off-topic…
I’ve had these caterpillars defoliate my roses for years. In addition to wondering about the identity of these little critters, I also was wondering:
if anyone else has dealt with them non-chemically
if those people had noticed any resistant species or hybrid roses
I posted a picture of the “bug” and its damage at the link below.
So far, I’ve noticed that they don’t seem to bother with Rosa rugosa much.
thanks for any help
Those are nasty things, unfortunately very common, called sawfly larvae. They aren’t true caterpillars, and do become a sort of fly in adulthood. I don’t spray for them or any other insect; I do remove a lot of them by hand and they eventually go away each season. Last summer, I noticed that they lay their eggs by “stinging” the leaf, and leave behind a small, off-colored and papery little pustule from which the larva emerges. If you squish that lightly with your fingernail you’ll kill it before it can do any more harm.
I wish I knew for certain which varieties they don’t like, but at this moment I’m not sure. They’ve changed their eating habits here, preferring certain roses in some years then leaving those alone to dine on previously unharmed varieties. Sadly, they are just one of many creepy crawlies that like to eat my roses, and true caterpillars are abundant enough in early summer to do a lot of damage with or without the sawflies’ help. Bt would work as an organic remedy for them, but it’s so expensive; it only works on caterpillars, though, and would probably have no effect on the sawflies. I’ve heard of people dusting plants with flour, which will expand in the gut of a caterpillar and kill it; maybe that would do the trick for sawfly larvae (it certainly can’t cost much to try). Barring something similarly creative, the only alternative may be to spray smartly with the least toxic chemical that will kill them and only spray when they’re present. I’m unsure of its relative safety and don’t necessarily trust all natural products to be harmless, but you might look into pyrethrin for the job if it comes down to that.
“1. if anyone else has dealt with them non-chemically”
This may seem odd but I raise Japanese Silky Bantam Chickens (mini-flightless chickens)and havent had any problems with terrestial pests since. Also, R. rugosa can get caterpillars. Ive seen damage on mine a few years back to Rugosa Magnifica and Snow Owl.