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Seasonal temperatures affect the stability of insect populations

By Anne Craig, Communications Officer

New research out of Queen’s University reveals how insects react to changes in seasonal temperature and may lead to new ways of controlling pest moths. William Nelson’s (Biology) research has shown tortrix moths experience an unusually large outbreak in population numbers when the temperature rises above 15 degrees Celsius, but are relatively stable when it’s cooler. Dr. Nelson and his collaborators used a combination of mathematical modeling and analysis of moth outbreak cycles to demonstrate the impact of temperature on population cycles.

“That reproduction and development rates change with temperature is well known,” says Dr. Nelson. “But we were definitely surprised that this warming was responsible for outbreak cycles.”

Tortrix moths, which include the grape berry moth and the codling moth, currently threaten crops in the United States and Canada.

Interest in the tortix moth came about because of the remarkable dataset in the smaller tea tortrix in Japan. Tea tortrix larvae feed off the leaves of tea and coffee plants and roll them up using silk. This decreases the value of the crop. Japan experienced over 200 outbreak cycles in 51 years. Using statistical analysis on the data and a mathematical model of the insect life-history, the researchers were able to show that temperature was responsible for changing the system’s stability twice a year.

“Our work highlights the critical role temperature plays in determining generation cycle outbreaks which will help us understand how pest insects are likely to respond to ongoing and anticipated climate warming.”

Over the next five years, Dr. Nelson and his collaborators from the United States (Dr. Bjornstad at Penn State University, USA) and Japan (Dr. Yamanaka at National Institute for Agro-Environmental Sciences, Japan) will conduct a series of experiments to test different ways to manipulate the insect’s life-history to re-stabilize the population and prevent outbreak cycles.

His work was published in the most recent edition of Science.