Driving the roads of south-eastern Australia motorists are not only confronted with green roadsides more often seen in spring but more noticeably thousands of small, white butterflies.
Poetic comparisons have been made in parts of Victoria with snowfall, so dense have the numbers of fluttering white wings been.
People have questioned whether the huge numbers of cabbage butterflies, well known for their distinctive white wings with black dots, two for females and one for males, reflect some sort of climate signal in the offing, but an entomologist has said there is a far more prosaic answer.
"It is very simple reason we're seeing so many cabbage white butterflies about," said Cesar Australia entomologist Paul Umina.
"We've had just about ideal conditions for them to build up, with a relatively mild winter followed by heavy summer rain which has meant there has been a lot of green material for the caterpillars to feed on," Associate Professor Umina said.
"The butterflies went pupal prior to winter last year then after the winter we saw good numbers in spring, which even though it was on the dry side still saw enough feed for the caterpillars.
"This meant there were good numbers prior to the summer rain and then, because the butterflies are able to lay up to 800 eggs each, they can breed up in pretty large numbers really quickly."
"In regards to It has been warm without being really scorching, there is moisture and green pick around so the conditions have been very good for them."
"What has been notable is that they have probably got the jump on their predators, those beneficial parasitic wasps in particular that lay their eggs on the caterpillars, although they will eventually catch up with the population."
Associate Professor Umina said the wet harvest has led to a lot of volunteer canola emerging, which was perfect for cabbage white butterflies, also known in some quarters as cabbage moths although they are technically a butterfly.
"They obviously love brassicas as a food source, but they will feast on leafy greens of all sorts, people with vegetables, especially things with large leaves like zucchinis, will notice damage."
Associate Professor Umina said coming out of season the damage to volunteer canola was unlikely to concern grain growers, however he said livestock producers with summer forage brassica crops would be less impressed.
The butterflies will consume most of their food in the larval stage as caterpillars before their brief life as butterflies where they consume mostly nectar.
Ass Prof Umina said numbers would continue to remain elevated while the conditions remained favourable.
Gregor Heard
Gregor Heard is ACM's national grains industry reporter, based in Horsham, Victoria. He has a wealth of knowledge surrounding the cropping sector through his 15 years in the role. Prior to that he was with the Fairfax network as a reporter with Stock & Land. Some of the major issues he has reported on during his time with the company include the deregulation of the export wheat market, the introduction of genetically modified crops and the fight to protect growers better from grain trader insolvencies. Still involved with the family farm he is passionate about rural Australia and its people and hopes to use his role to act as an advocate for those involved in the grain sector.
Gregor Heard is ACM's national grains industry reporter, based in Horsham, Victoria. He has a wealth of knowledge surrounding the cropping sector through his 15 years in the role. Prior to that he was with the Fairfax network as a reporter with Stock & Land. Some of the major issues he has reported on during his time with the company include the deregulation of the export wheat market, the introduction of genetically modified crops and the fight to protect growers better from grain trader insolvencies. Still involved with the family farm he is passionate about rural Australia and its people and hopes to use his role to act as an advocate for those involved in the grain sector.
