green caterpillar on a green leaf
Image credit -

Believe it or not, caterpillars can cause absolute devastation within the garden, but because they're not as obvious to the naked eye as slugs or have characteristic bite marks such as the dreaded vine weevil they often get away with the damage they inflict blame free.

parasitic wasp attacking brown caterpillar
Parasitic wasp - image credit
Of course, a small amount of damage is neither here nor there, and if you are talking edible crops a few holes does not stop your plants from being edible. Furthermore, if you control your caterpillars in such away that they don't survive then you are denying the environment the adult butterflies which are in the majority of cases important pollinators. But there is another side this coin. Given the right environment and if left uncontrolled infestations of certain caterpillar species can quickly explode in the locale and in such cases economically important crops will be lost.

While caterpillars are extremely adept at hiding within the foliage, arguably the best technique to controlling caterpillars is to cover with a protective fleece or netting. This is fine for the allotment but impractical in an ornamental flower garden.

In the garden the most organic method is still to pick them from the plants by hand. Finding them is the difficulty but their presence is betrayed by irregular holes and large, dark green droppings. If doing it yourself seems like an awful lot of hard work then why not employ nature. Encourage insect eating birds into your garden by providing water, nest sites and appropriate foods.

This is one product which you can spray on you plants which is caterpillar specific and won't kill other beneficial insects. The product is called Dipel and contains the bacterial Bacillus thuringiensis. The bacteria works as a bacterial stomach poison for all caterpillars.

parasitic wasp eggs attached to green caterpillar
Parasitic wasp egg cases - Image credit
Tip 1. If it is the caterpillar from the cabbage white butterfly that you are hoping to control then try this old gardener's tip. Place broken eggshells from white eggs only around your susceptible crop. It is believed the the butterfly mistakes the shells for other cabbage white butterflies and flies on to an area where the competition is less.

Tip 2. Sometimes it is easier to search for caterpillars at night using a torch to find their the caterpillars themselves or locate them using their shadows.

Tip 3. If it is a particular plant that is showing susceptibility to caterpillar damage then place white card or plastic below the plant and shake out the branches. Collect and dispose of fallen caterpillars.

Tip 4. Use companion plants that are known to deter specific butterfly species from your crops. Predatory wasps that will actively seek out and caterpillars can be attracted to your garden by planting lemon balm, parsley, chamomile, peppermint and catnip.

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