White cabbage butterflies: the scourge of the garden

02:14, Mar 13 2013

What to say about white cabbage butterflies? They're just plain awful. They laid their eggs on the under side of the leaves of my cavolo nero plants, and their babies have feasted on the leaves until there is nothing left but stumps. The butterflies are out and about now, and they love to eat your brassicas (cabbages, broccoli, kale, brussels sprouts), so unless you want to end up with just stumps in your garden, there are measures you can take. 

1. Squish the blighters. I spent hours last autumn picking them off my broccoli crop, and as this year I'm planting more brassicas than ever, I can only assume I'll spend hours and hours more scanning the leaves for green caterpillars. It is a drag, but for me actually kind of relaxing. At least last year I could feed them to my chooks, this year they'll be getting squished the old-fashioned way.

2. Create a forcefield between the butterflies and your plants. You can use netting, like old net curtains. Just make sure that there are no eggs or tiny caterpillars on your plants before you put the netting up.

3. Derris dust. Now we're getting serious. This is a pesticide called rotenone that you apply to the leaves of the plant. It's plant-derived, and has been classified as moderately hazardous by the World Health Organisation

4. I've heard that white cabbage butterflies are territorial, and will not go near another butterfly's turf or airspace. Putting up string with small pieces of white plastic cut from a yogurt pottle could deter them, though I haven't tried this myself.

5. What worked well for me last year was planting my brassicas a little later in the season when temperatures were lowering and the butterflies had done their dash for the season. That and a regime of squishing them worked well for me.

Do you have white cabbage butterflies or caterpillars? Are they wreaking havoc on your brassicas? What do you do to tell them to get lost?

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