Is something munching on your leafy greens? Be it broccoli, kale, cauliflower, turnip leaves, even spinach?
I have had a number of questions in the last few weeks from customers growing their own veggies in relation to damage to leaves - what is causing it and how best to deal with it. In all cases when we delved deeper, it seems it was the caterpillar of the white cabbage moth. If you have noticed a white butterfly in your garden, it is likely this is the culprit, laying eggs on primarily brassicas (kale, turnips, rocket, broccoli, cabbage but also on many other crops) which hatch into green caterpillars and begin munching on your leaves for quick growth. The caterpillars have a very effective camouflage, so you will need to look closely, and on both sides of the leaves. They can be large and juicy, or tiny and inconspicuous, depending on their age. Regardless, they will chew holes into your prized vegetables.
There are four main ways to counteract them:
Net the entire crop as soon as you notice the white butterfly, which will stop them being able to lay their eggs. Ensure their are no holes or gaps in the net, otherwise you may inadvertently trap the butterfly within your precious crop.
If netting is not an option, or you missed the window, inspect leaves daily, both top and underside for caterpillars. They will range from newly hatched through to large and meaty. Pick them off the leaves and either squash them (not an elegant task) or give them to your chooks; they will love them.
Use a biological control in the form of Dipel (a powder mixed with water), or a homemade control such as chilly or garlic spray.
Allow some damage to occur in order to attract beneficial insects who will do the work of controlling the caterpillars (and other "bad" bugs) for you. The image below shows a well camouflaged green caterpillar which will be devoured by the offspring of a parasitic wasp, once the white eggs hatch. The offspring take the nutrients they need from the caterpillar to grow to maturity, reproduce and then overwinter in the soil to start the process again next year. Whilst this seems like a long process, as each new generation hatches and reproduces, you will see less and less caterpillars. Keep an eye out for these white elongated eggs and celebrate your chemical free garden when you see them.