Spray Plants with Water, Find Out Which Insects Are on Them Using New DNA Method

OSAKA — By spraying water on plants, a method has been developed to identify insects and other arthropod species on plants by collecting trace amounts of DNA contained in feces and saliva that remain on leaves and stems, a group of researchers including a Kindai University lecturer has announced.

There are hopes that this method can lead to efficient pest control and biodiversity surveys.

The paper on the method was published in international science journal Scientific Reports on Friday.

Surveying insects and other arthropods on plants has usually required methods such as catching them in traps or visually confirming them. Such methods are not only labor intensive, but many small arthropods are also difficult to find through visual surveys.

The team focused on environmental DNA (eDNA), which refers to DNA in excrement and body fluids originating from organisms that are released into the environment, whether rivers, ocean or soil. For example, analyzing river water could lead to identifying what fish are living there.

The team sprayed water on 37 samples of eggplants and cabbage plants and collected the water that flowed over the surface of leaves and stems. The team visually spotted seven species, including larvae of moths and aphids. However, by analyzing collected water, DNA for 22 other species that were not visually observed, including mantis and grasshoppers, were identified. The team said analysis of collected rainwater that flowed over the surface of the plants also led to a similar result.

“We were able to detect DNA of arthropods that we may have missed when checking or that had already left the plants,” Kindai University Lecturer Kinuyo Yoneya said. “This method can also be applied to trees.”

“It is an interesting idea to collect eDNA by spraying water,” said Tohoku University Prof. Michio Kondo, an expert on community ecology. “Since data can be obtained easily, the method could be useful for such matters as pest infestation forecasts in the future.”