YOU may have seen these white butterflies, in your garden, on the street or flying onto your car while driving along the Murray Valley Highway.
And while they do look beautiful fluttering about, they present a clear and present danger to vegetable farmers.
Cabbage butterflies, better known as cabbage moths, are a common pest during summer and autumn, but this year’s weather conditions have caused a population explosion – making them a serious challenge for farmers to control.
Peter Shadbolt from Scotties Point Farms in Beverford grows onions, beetroots and broccoli, and said he feared for the damage his recently planted broccoli crops may suffer.
“It’s a little bit of an unknown, just exactly what’s going to happen as we move forward,” Mr Shadbolt said.
“In most cases it is an easy moth to control compared to other pests, but just sitting here I can already see 50 of them on my front lawn right now, so we going to have to be a bit more diligent this year.”
Mr Shadbolt said he worried about the butterflies laying eggs in his crops.
“The main concern will be the grubs in the broccoli, it’s not the moths that do the damage,” he said.
“Once the butterflies lay eggs in the broccoli, then we can’t tell because it’s inside the plant. So we’ve got to make sure we’ve got a good spray program to minimise it.”
Cesar Australia extension scientist Lilia Jenkins said the influx of cabbage butterflies this year had been triggered by a winter that was not cold enough, and winter was when most of them die.
“They are quite a common pest in general, but due to the really mild winter, it was easier for earlier generations to survive and their numbers have had a good chance to build up,” Ms Jenkins said.
Cabbage butterflies are largely harmless, but in their green caterpillar stage is when they decimate brassica plants like broccoli, cauliflower, cabbages, kale and bok choy.
“It can be quite easy for the caterpillars to do quite a bit of damage to vegetables, such as damaging young seedlings or causing defoliation,” Ms Jenkins said.
“The adults will lay their eggs anywhere they can but usually on the underside of the leaves.
“Then, the eggs will hatch and the caterpillars will eat ferociously until they turn into butterflies and the cycle repeats.”
At the same time she cautioned farmers about any serious use of insecticides to control the problem.
“Generally we say to try to avoid spraying if you can, especially with the really active pesticides because they can wipe out all the beneficial insects in the crops as well, which help control the numbers of pests,” she said.
“We should try and give them a chance to do their job as well so we’re all working together.”
