The appearance of white butterflies around Spring in my garden signifies one thing: the quiet but deadly march (and munch) of the 's larvae. The first sign of an impending chomp fest are the orange-coloured egg sacks which you can find, carefully hidden on the underside of brassica leaves. Before you know it your brassicas are depleted or, if they are seedlings, completely destroyed except for the poor, denuded stalks which wave apologetically in the air. It's not their fault, the White Cabbage larvae is clearly a force to be reckoned with, but is there an organic way to prevent these greedy grubs from decimating your cabbage or broccoli crop?
The key, as with growing all plants, is observation. Keep a regular check on your brassicas, gently lift each leaf and check carefully for the presence of the grub. The larvae by now has grown out of the egg and developed the same colour as the broccoli, or cabbage and so can be extremely difficult to locate (see image). Once located though, the rest is easy. Simply pick off the fattening grub and dispose of away from the plants.
Regular checking is necessary to ensure the larvae is removed before there is too much damage.
Another way to reduce the threat of the larvae decimating your crop is to encourage natural predators. These include wasps and some bugs but also include grub eating birds. Happily these include chickens and ducks who regard the larvae as a special kind of delicacy. You may be lucky enough to find yourself in a win-win situation with the chooks and ducks: they get rid of the grubs and also deliver their rich and powerful fertiliser to the garden! To paraphrase permaculture founder You don't have a White Cabbage Butterfly problem, you have a duck deficiency. Interestingly red-coloured varieties such as red cabbage and kohlrabi rarely seem to have problems to the same extent as do the dark green varieties. This is probably because they offer less camouflage. Should your White Cabbage Moth larvae infestation become unmanageable, consider switching to these varieties.
Lastly using a physical barrier to the seedlings with prevent the problem in the first place. Protective grow cover material or guards will offer protection against the butterfly being able to lay its eggs in the first place.
Perhaps you have encountered similar problems with this pest?
If so, do you have any organic ways of getting rid of the White Caterpillar Moth's larvae?
Please let us know either here in our comments field or join the discussions over at our Facebook page.
Also don't hesitate to contact us here at Evergreen Growers should you have any questions on growing and the establishment of tube stock.
We'll be publishing a number of articles of tube stock and its benefits in the coming weeks, don't forget to keep an eye out for them.