Diamondback moths are a farmer's worst enemy
DECEPTIVELY named, the diamondback moth is anything but precious.
The pest is usually treated with chemicals but warmer weather is helping it develop a resistance to the type of chemical many growers are using.
While it normally hibernates in the colder months, uncharacteristically warm winters are allowing the moth to continue to breed and build immunity to group 28 insecticides.
A twofold problem, hotter weather decreases the moth's lifespan, allowing generations to produce offspring more rapidly.
Bureau of Meteorology meteorologist Jess Gardner said the climate for the next three months was expected to be warmer than average throughout eastern Australia.
"We're looking at a high chance of greater than average minimum temperatures for the whole of Queensland,” she said.
David Simon grows cauliflower, broccolini, shallots, womboks and radicchio on 220 acres across three Lockyer Valley properties.
Notoriously targeting the brassica family, the moth infested his crops at the end of last year.
"Our agronomist got on it pretty quickly,” Mr Simon said.
He said the moth was a part of nature and for the most part was kept at bay with pesticide.
But the chemical combination he had been using was beginning to fail as the pest developed an immunity.
"They built a bit of resistance to the group 28 insecticides,” he said.
He said the moth had been laying eggs on the crops, resulting in larvae crawling on the produce and eating the plant.
"They chew the crop to bits,” he said.
"They don't really chew the flowers, they chew the plant.”
Mr Simon said the pest hid in the vegetable, making it difficult for him to sell the product.
"They're a little green grub and there's lots of them,” he said.
"Nobody wants to buy products with little green grubs in them.”
Mr Simon said his agronomist walked through the paddocks checking the produce for the moth's eggs.
"When it gets really cold, they disappear,” he said.
"They've got certain times of year where they're more prevalent, like this time of year when it's a bit warmer.”
Chemical fails to kill pest
WARMER winters are allowing a pest that normally goes into hibernation during winter to continue to breed and infest crops through Queensland's cooler months.
Continuing to thrive throughout the period during which it would normally decline has allowed the diamondback moth to develop an immunity to pesticide.
Lockyer Valley agronomist of 17 years Mark Parkinson said rotating through chemical groups could help keep the larvae at bay.
"What's been going on is that the larvae are becoming immune and that's because we've been using too much of the same chemicals,” Mr Parkinson said.
"We need to be rotating between old and new chemistries along with the biologicals far more frequently.”
He said the diamondback moth was known for infesting brassica plants, including the likes of cauliflower, wombok, broccoli and cabbages.
"It gets underneath the head as it's growing and you can't get them out,” he said. "Then they're unsaleable because there are too many live larvae in the head.”
He said the moth wasn't new to the region but that rising temperatures were making it trickier to combat.
"It really showed its head last year or the year before and we tried to find out why it was happening,” he said.
"It turned out a lot of growers were using the same chemicals over and over and over again.
"I was changing things around and I wasn't having anywhere near the problem.”