More than half of the world’s population feed on rice. But pests like rice leafhoppers can cause huge losses in global rice production every year. And pesticides these days only lead to more ecological problems than they solve.
Scientists have looked in the plants themselves for an answer for more effective and environmentally friendly methods of pest control.
Rice plants can naturally release more and more “linalool” – an invisible, volatile substance – when they are bitten by cicadas. The substance can effectively attract the cicada’s natural predator – parasitic wasps – to kill the pests.
Based on this well-known self-defense mechanism of rice plants, Professor Lou Yonggen and his colleagues from east China’s Zhejiang University tried to get rice plants to release more linalool before they were attacked by pests. The chemical and biological activities may be complicated, but the logic behind this concept is plain and simple – “the enemy of my enemy is my friend”.
Over the years, Lou and his team have experimented with many small molecular compounds to find one that can make a rice plant significantly increase the amount of linalool it releases. Eventually they came across one called 4-fluorophenoxyacetic acid. This laboratory-made substance was mixed into the soil and gradually absorbed by the roots as the plants grew. Lou’s team successfully measured an increase in the amount of linalool released by the treated rice plants, and to their surprise, the cicadas died soon after in the laboratory, even in the absence of parasitic wasps.
The treated rice plants developed a new self-defense ability that helps them form a thick layer of physical barriers in their stem cells to block the penetration of the penetrating mouthparts of rice plant hoppers. The pests didn’t die from the increased amount of linalool in the environment, they all died from starvation instead.
Today, that tentative lab success is still about to emerge from the labs and be widely applied to farmland, which can still be a long way off. The two options are either to spray the leaves of rice plants with this artificial substance or to develop a molecular mechanism and use it to genetically modify rice plants. In any case, scientists believe this technology has the potential to revolutionize the cultivation of rice crops around the world.