Study: Marigold substance a natural killer of garden pests

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KASUGAI, Aichi Prefecture–A substance released from Marigold flower roots seeps into the skin of nematodes and kills the plant-destroying worms, a finding that could lead to natural pesticides that do not harm the environment, researchers said.

The team, headed by Koichi Hasegawa, associate professor at Chubu University specializing in applied entomology, said its study clears up the mystery of how the substance, alpha-terthienyl, attacks nematodes in the soil.

Nematodes are abundant worm-like pests that enter plant roots and steal their nutrients.

The Chubu University researchers applied various densities of alpha-terthienyl to nematodes. When the density level was about the same as in soil around Marigold roots in gardens, nearly 80 percent of the nematodes died. At a higher density level, almost all nematodes were killed.

Nematodes have tough skin and usually keep their mouths closed.

The study revealed that alpha-terthienyl does not enter the mouth.

“It was found that the substance entered the nematode from its skin, not from its mouth, and attacked the nematode,” Hasegawa said. “If the study develops, we might be able to take measures against damaging pests with less burden on the environment.”

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