Diamondback moth, one of the most serious pests attacking brassica crops around the world, is enjoying favourable conditions in Australia thanks to recent weather patterns, increased canola cultivation and the use of synthetic pyrethroids and may only become more difficult to control in the future.
The GRDC reports that Dr Mike Furlong of the University of Queensland said research and information on the ecology of diamondback moth in the canola landscape was limited, so scientists were learning from the experience of Australia's horticultural industries with the pest.
Dr Furlong works with the National Invertebrate Pest Initiative, which is supported by growers and the Australian Government through the Grains Research and Development Corporation (GRDC).
"The canola landscape in Australia has changed drastically over the past 15 years," Dr Furlong said.
"The area sown to canola in Australia is about a million hectares today, compared to perhaps 70,000ha 15 years ago.
"Diamondback moth persists throughout the year in some horticultural systems, but in broadacre situations persistence is more difficult for them.
"We're investigating how diamondback moth persists outside the winter cropping season, and developing climate-based models to predict future outbreaks.
"At this stage we really only have anecdotal evidence, but it's quite possible that they’re surviving on weeds and moving into canola crops during the growing season."
Diamondback moth larvae usually feed on the leaves of canola plants but can also attack flower buds and pods, resulting in reduced yields.
"Diamondback moth favours warm temperatures – heavy rainfall can cause a lot of mortality among the eggs and larvae," Dr Furlong said.
"Warmer temperatures, which might be exacerbated by predicted climate change, could provide even more favourable conditions for the pest.
"It certainly seems to have become more of a problem than it was in the past.
"In addition to more canola and warmer temperatures, the use of synthetic pyrethroids to control mite infestations may also be killing off natural predators of diamondback moth.
"This practice could also contribute to the evolution of insecticide resistance in the pest."
Dr Furlong said the diamondback moth was notorious for evolving resistance to insecticides.
But he said generalist and more specialised predators could have a big impact on diamondback moth populations.
"There are several species of parisitoids, such as the parasitic wasp Diadegma semiclausum, which have been introduced from New Zealand," he said.
"They're widespread in Australian horticultural systems but again, we have little information on their presence and impact on diamondback moth populations in the canola landscape.
"Generalist predators such as spiders can also have a big impact and they are present in canola, but we don’t know to what extent or how they affect diamondback moth in canola crops."
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