“It is a greater act of faith to plant a bulb than to plant a tree.”
Clare Leighton, Four Hedges (1935)
Garden Lore: Cabbage whites and brassicas
Brassicas are like ambrosia to the cabbage white butterfly. Or maybe heroin. For this reason, we prefer not to grow brassicas during the summer months when the cabbage whites are at their most active. I am a reluctant consumer of cabbage, broccoli and cauliflower at the best of times. The latter two are passable in a winter soup flavoured with cheese (blue cheese is the classic, but any cheese helps). However, many of the increasingly popular Chinese greens also belong to the brassica family, and these are acceptable to me at any time of the year.
You can net the vegetables, but the netting needs to be raised clear so that the winged parent cannot land and lay eggs through the netting. If you want to spray, talk to your local garden centre about BT (which is a bacterial based treatment) or pyrethrum-based options. Pyrethrum is the active ingredient in flyspray and was originally extracted from a daisy. These days it is more likely to be synthetic but it remains a pretty safe control. Vigilant digital control (squashing with the fingers on a daily basis) can work in the early stages. We think it is a myth that egg shells on sticks will confuse the butterfly and they will fly away. White butterflies show no territorial instincts at all, that we have ever seen.
If you don’t like added protein to your cooked vegetables (while Mark does not mind the odd cooked caterpillar, most people find them very offputting), you can sprinkle lots of salt over the florets or leaves as you prepare them, then cover them with cold water for a few minutes while the caterpillars die. Rinse them thoroughly, inspect closely and cook with no added salt.
First published in the Waikato Times and reprinted here with their permission.