Caterpillars

Caterpillars are the larval form of butterfly which are in essence eating machines to enable the larva to transform into a chrysalis or pupa then again into a butterfly.  There are over 70 different species of butterfly in the UK.  Some are far more common than others but in gardening terms, all develop in a similar way.

Do they harm plants?

Yes, but not generally fatal.

What damage do they cause?

Generally, butterflies appear mostly in Summer months, so 'at risk' plants need to be checked generally late spring through to Autumn.  Generally, the plants which caterpillars eat from will recover, although what is left of the eaten leaves are lacy skeletons and larger stems which do not look cosmetically pretty.

Do they affect certain plants?

Caterpillars are very specific with what they eat.  They tend to only eat leaves from particular plants. For example, the common Cabbage White caterpillar will feed only mainly on cabbages, broccoli, cauliflowers, wall flowers and nasturtiums for example.

How do I get rid of them?

It is worth noting before you embark on eradicating every caterpillar in your garden that butterflies which are the result of caterpillars indulgence are a beautiful site to watch, and can provide a welcome splash of colour to the garden through many months of the year.

Non-chemical control

Keep an eye out for individual or small clusters of eggs on the underside of plant leaves, then caterpillar damage after the eggs have hatched and remove by hand.  They have many natural predators including Birds, frogs and toads so encouraging them will have an affect on the caterpillar population.  It is worth remembering that hairy caterpillars can cause skin rashes if they are picked up with no protection.

Caterpillar nematodes (Bacillus thuringiensis) are available and should be used when they are seen on the plant and the nematodes will seek out the caterpillars.  They are generally safe for edible plants.

Chemical control

Spray with pyrethum or bifenthrin.

Always use chemicals as instructed on the label and wear any gloves etc. when necessary.