Perhaps a sawfly. I know that raspberries get them. Look similar to caterpillars but aren't. So Bt won't work.

Take a look at TAKE DOWN GARDEN SPRAY.

Ron

Id try BT first.

Its organic and even if its a sawfly, it couldnt hurt to keep the pillars away.

Im sure you could find uses for it around the rest of your garden.

I got a little bottle of Safer BT a long time ago.
http://www.saferbrand.com/store/garden-care/5160
You mix such a little amount in the water that it seems to last forever :)

mgm, it's actually not a good idea to use Bt unless a caterpillar problem has started. It's one of those products that has become overused and abused, leaving many native moth and butterfly species endangered.

So, as with just about all pesticides, organic or not, we should use only when necessary, only as directed, and with consideration of the bigger picture.

rhizo, Thanks for your input!

I dont use it when butterflys are out, but native moths? Kill em all...

lol jk but i do use it when its pillar season. Its not worth letting them get ahold of my plants, or letting the borers in.