Whats eating my parsnip leaves

[thomasb]

Hi All,
Was down weeding my parnips this evening when I noticed that quite a few had small holes in their leaves. Some looked very badly eaten when numerous holes in the leaves. On closer inspection I noticed a small brown-coloured grub attached to the underside of the leaves. I would take my camera down another evening but the grubs are only 2-5mm in length and would therefore not come out very well.
Anyone any idea what likes parsnip leaves? I had thought there was few pests that affected them.
I went  along each plant and inspected. Where I found a grub I squashed it.
I am tempted to spray with deris or something if the suitation gets worst.

Thomas

[thomasb]