Caterpillers on my cauli plants

You will not need to do anything to the soil, Scotcat, but you are going to get dirty fingers. You need to go round your plants and squash all the caterpillars you can find! It is a messy job but gives the best solution.Spraying with soapy water can help but I don't find it to be too sucessful.

Thankyou hope eggs dont go right into soil and hatch more.

The butterfly lays the eggs on your cauli. leaves... they hatch and instantly start eating said leaves. They don't go into the soil at all. As B said keep going out and removing the caterpillars as you see them. B checks our brassicas on a daily basis checking for and killing them. In reality though if they are on your cauliflower they will do little harm as you eat the flower not the leaves.