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Locusts may choose where to invade based on temperature, researchers find Locusts may choose where to invade based on temperature, researchers find
(1 day later)
Researchers have discovered that one of Australia’s most damaging agricultural pests may choose where to invade depending on how hot it is, a finding which may allow them to predict where future outbreaks occur.Researchers have discovered that one of Australia’s most damaging agricultural pests may choose where to invade depending on how hot it is, a finding which may allow them to predict where future outbreaks occur.
Locust swarms cost the agricultural industry millions of dollars each year, and are particularly damaging in southern Queensland, New South Wales, Victoria and parts of Western Australia in the spring to autumn months.Locust swarms cost the agricultural industry millions of dollars each year, and are particularly damaging in southern Queensland, New South Wales, Victoria and parts of Western Australia in the spring to autumn months.
But University of Sydney biological scientist Dr Fiona Clissold found the area locusts choose to rest in and digest after feeding depends on the nutritional quality of the plant they just ate.But University of Sydney biological scientist Dr Fiona Clissold found the area locusts choose to rest in and digest after feeding depends on the nutritional quality of the plant they just ate.
“We found some plants are good quality foods for locusts when digested at high temperatures, whilst others are better when digested at cooler temperatures,” Clissold said.“We found some plants are good quality foods for locusts when digested at high temperatures, whilst others are better when digested at cooler temperatures,” Clissold said.
She and her colleagues examined two species of grass commonly demolished by locusts – Kangaroo grass, and wheat. She and her colleagues examined two species of grass commonly demolished by locusts – kangaroo grass, and wheat.
Kangaroo grass gives locusts a high protein diet at high temperatures and a high carbohydrate diet at low temperatures, she said. With wheat, the protein to carbohydrate ratio does not change with temperature, but locusts are able to absorb the nutrients more effectively at higher temperatures.Kangaroo grass gives locusts a high protein diet at high temperatures and a high carbohydrate diet at low temperatures, she said. With wheat, the protein to carbohydrate ratio does not change with temperature, but locusts are able to absorb the nutrients more effectively at higher temperatures.
“After eating, locusts sit for 30-40 minutes to digest their meal before feeding again,” Clissold said.“After eating, locusts sit for 30-40 minutes to digest their meal before feeding again,” Clissold said.
“Following a meal of Kangaroo grass, the locusts seek shady places, such as behind grass stalks or in burrows, in order to get a high carbohydrate meal. After eating wheat, however, the locusts sit in warmer areas to ensure a protein-rich meal. “Following a meal of kangaroo grass, the locusts seek shady places, such as behind grass stalks or in burrows, in order to get a high carbohydrate meal. After eating wheat, however, the locusts sit in warmer areas to ensure a protein-rich meal.
“A plant can be a poor quality diet at one temperature and a good quality diet at another."“A plant can be a poor quality diet at one temperature and a good quality diet at another."
Clissold will present her findings at the Society for Experimental Biology annual meeting in the US on Wednesday, to show locusts seemed to be driven by their ability to gain carbohydrate, contradicting current scientific belief that they are driven to gain nitrogen. Clissold will present her findings at the Society for Experimental Biology annual meeting in Britain on Wednesday, to show locusts seemed to be driven by their ability to gain carbohydrate, contradicting current scientific belief that they are driven to gain nitrogen.
But a high carbohydrate diet allows locusts to grow bigger, fly further and do more damage, Clissold said.But a high carbohydrate diet allows locusts to grow bigger, fly further and do more damage, Clissold said.
“When temperatures are hotter and food quality is good, locust plagues are more likely to occur as the locusts can develop more quickly and thus get more generations in per season, rapidly increasing the population,” she said.“When temperatures are hotter and food quality is good, locust plagues are more likely to occur as the locusts can develop more quickly and thus get more generations in per season, rapidly increasing the population,” she said.
If scientists could better understand the traits in plants that prevent insects gaining the nutrition they need, as well as what occurs in the gut after ingestion, plants could be selected or genetically modified to be unattractive food sources for the insects, she said.If scientists could better understand the traits in plants that prevent insects gaining the nutrition they need, as well as what occurs in the gut after ingestion, plants could be selected or genetically modified to be unattractive food sources for the insects, she said.
It would be a coup for the farming community, with the problem so bad that in 2010 the Victorian government announced it would invest $43.5m to tackle the pests, while South Australia allocated $12m.It would be a coup for the farming community, with the problem so bad that in 2010 the Victorian government announced it would invest $43.5m to tackle the pests, while South Australia allocated $12m.
The work of Clissold and her colleagues could also have implications for climate change. She said increases in temperature in Australia could alter the crops that pest species currently attack, or even lead to new pest species.The work of Clissold and her colleagues could also have implications for climate change. She said increases in temperature in Australia could alter the crops that pest species currently attack, or even lead to new pest species.
She said scientists and the general public were increasingly aware of the importance of climate change being considered as part of current and future research.She said scientists and the general public were increasingly aware of the importance of climate change being considered as part of current and future research.
“Unfortunately the people making decisions seem to want to ignore the research and worse still shut it down,” she said.“Unfortunately the people making decisions seem to want to ignore the research and worse still shut it down,” she said.
She and her team are now examining how climate change may affect dietary preferences of herbivorous insects in general.She and her team are now examining how climate change may affect dietary preferences of herbivorous insects in general.
• On 3 July 2014 this article was amended to name the country hosting the Society for Experimental Biology annual meeting as Britain. A previous version said it was taking place in the US.