I started tidying up my flowerbeds yesterday and discovered alot of grubs - i think they are leatherjackets - in the soil. Some of my plants are struggling and look a little under attack. Im guessing that they have been eating away at their roots.

To give an idea of how many there are, if you took a double handful of soil from the beds, you would probably have a grub in it, perhaps two.

How do i get rid of them? I can use a chemical pesticide if needs be, but the only one i am aware of is one that you apply on lawns in the autum to kill them before they become grubs.

thanks