Before you roll back your sleeves for some autumn/winter planting, we need to have a little chat about white cabbage moths and butterflies… honestly, we don’t want you to witness another brassica massacre this season. One day you’re looking at your brassicas with adoration, the sun is shining, the birds are chirping, it is as if you can hear a heavenly choir praising your garden... NEXT MINUTE the breaks come to a SCREECHING HALT as some eating machines have devoured your greens. It’s a shame that the caterpillar of white cabbage moths share our appetite for cool-season crops.
The real strength of the white cabbage moth is its stealth, because the caterpillars are green – yes, exactly like the foliage of your plants – and extremely difficult to spot. But when your eyes shift focus, there they are, all over your kale, broccoli and rocket and their namesake cabbage, getting fatter and fatter as each day passes.
As soon as you begin to spot the caterpillars, you realise what the black little dots are that collect in the stems of your plants. That’s right, their shit! The eating habits of the caterpillars and breeding frequency of the moths are both so supreme that overnight – quite literally – a few tiny green caterpillars will transform into a green shitting army of brassica-devouring devils.
The best method is always prevention and if you are lucky enough to not have an infestation, secure your garden with a finely woven net immediately. Although the moth itself is superficially harmless, it is probably having a wild romp in your veggie patch and laying its eggs with reckless abandon. Shop insect netting
Hunt and Gather
If your plants are already showing signs of caterpillar damage- the rapid appearance of holes or loss of entire leaves - a simple method is to hunt and gather the offenders by hand. Check the dense centre of plants and inspect the underside of the leaves. Collect as many as you can and dispose of them in whatever way you deem to be the most humane. We get a worrying amount of pleasure from tossing them to our chooks and watching the inevitable feeding frenzy that ensues.
White cabbage moth sniff out the brassicas in your patch. Throw them off scent by planting aromatic plants such as rosemary, sage, dill, chamomile, mint, even onions! Dill is also known to attract parasitic wasps who’s favourite snack happens to be caterpillars, win win!
One of the most effective and easily available natural insecticides. The active ingredient of Bacillus thuringiensis var. kurstaki is derived from beneficial bacteria found in soil, on plant surfaces, and also in insects. Dipel is toxic to caterpillars, but completely harmless to humans, birds, and beneficial insects such as ladybugs and bees. Simply mix a sachet with water and spray infected plants. Repeat the application over a few days (and after any rain) and be sure to spray the underside of leaves. When caterpillars ingest sprayed leaves it can take a couple of days for them to die.
Butterflies are territorial creatures – like the neighbourhood possum – and if a patch is occupied, they usually abide by the gentlemen’s rule of ‘do not enter good sir’. They also have very poor eyesight. This means they will be deterred by some simple dummy butterflies. When making your dummy butterflies, don’t assume all white cabbage moths play fair. Rather than putting one in the patch, hoping the gentlemen’s rule is followed, make it look extremely busy and intimidating.
Before you yell Yipee Ki Yay and destroy every living thing you think is trying to eat your plant, take a breath, step back and wait. Natural predators are often not too far behind their food source. Sometimes as gardeners we are too reactionary before letting nature take its course. That said, if the scales are tipping in the cabbage moth and butterflies’ favour - which it often does - you now have all the tips and tricks to avoid another brassica massacre this season.