Black vine weevil larva for id.

[Bruce Williams]

Originally posted in main insect forum in error. Now off page1 without response so thought I'd try my luck in the proper forum:

Northants garden. Probably fatal damage to five Heucheras. The roots are all but mush and the leaves are dead or floppy. I've cleaned them out and picked the larvae out of the roots (think I've got em all). Re-potted into new containers. Blackbirds have been feasting on the grubs in old containers.

Here's one of the larva (still very much alive). I'm pretty sure this must be the Black Vine Weevil grub as I've read that it's the main pest of this group of plants.

Pic2 shows the head from above and pic3 shows the underside (mouthparts) of the head. The jaws were constantly opening and closing so it's easy to see how this grub can do so much damage.







Confirmation of id appreciated as would be any advice for avoiding this pest in the future.

Bruce

[Hedera]

Yes, vine weevil! They like pot plants, especially heucheras. The only treatment I've found that works is to water with Provado. The weevils are coming out about now and crawl into other pots to lay eggs - I found one the other day.

[Dawn01]

These are also particularly partial to fuschias, primulas, and dahlias, amongst other things. If you don't want to use chemicals (I steer clear of Provado for containers anywhere near the pond) you will have to keep an eye out for damage to leaves, (the adults chew notches in them), then come out with a torch at night and catch the adults.
Once you have this pest in containers it's very difficult to get rid of, especially as they are around in the ground anyway, where, not being confined they do far less damage, so you aren't so aware of them.
I find the best thing to do is to re pot susceptible plants early in spring, before the weevils have eaten too much of the roots, and the plant has a chance to recover.

[Bruce Williams]

Hedera - Thanks for confirmation of id and helpful advice - on the strength of which I bought a packet of Provado this afternoon.

Dawn01 - Thanks for the info and advice - I lost a couple of hardy fuschias over winter so I'll also check them for signs of vine weevil (thought the cold winter had done em in). I plan to buy replacement heucheras and will try repotting early spring 2012 as you suggest (I'll also use the Provado).

Bruce