Host plants tell insects when to grow longer wings and migrate

July 2, 2018, Washington State University

Scientists at Washington State University and China Jiliang University have discovered that the quality of the host rice plant determines whether the brown planthopper, a major pest on rice in Asia, grows short wings or long wings.

Wing size determines whether the insect can fly long distances to other plants or stick around and feed off nearby rice plants, said Laura Lavine, professor in WSU's Department of Entomology.

"It's all about the amount of glucose, or sugar, in the plant," Lavine said. "Rice plants with higher glucose levels are older and dying. That increase in glucose causes adolescent brown planthoppers to develop into the long-winged adults. The plant really is telling the insect how to grow."

The findings, published in theProceedings of the National Academy of Sciences, give scientists a potential tool in engineering ways to fight the pest.

More sugar, time to move on

Over the life of a rice plant, the ratio of sugars to amino acids changes. During the early growth stage, rice plants are a great food source for insects. These young rice plants have relatively low glucose levels and brown planthoppers don't need to search out a new home. They develop with short wings and, in females, large ovaries. The young plant is healthy and provides plenty of nutrition for the insects to survive and reproduce.

But as the plants age, the glucose levels rise. This triggers a change in the young brown planthoppers. They develop with long wings and small ovaries, preparing to migrate away from the old, less nutritious rice plant in search of better food.

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