Pesticide Changes How Crops Talk, React: Study

It sounds like science fiction, but University of Guelph researchers have found that crops can “talk” and “make decisions” about their growth – and that a pesticide can change their plans and improve their growth.

The research team led by Prof. Clarence Swanton, Plant Agriculture, found in two studies that crops communicate and react to other plants such as weeds growing around them — even before the crops poke through the soil surface.

In another surprising result, the researchers found that treating corn seeds with thiamethoxam, a commonly used neonicotinoid pesticide, enhances early crop seedling growth.

Corn normally reacted to weeds by slowing its own growth, even before reaching the soil surface. The researchers found that occurred even when the weeds were not direct competitors for water, fertilizer or sunlight.

But treating corn seeds with thiamethoxam overrode that reaction and triggered expression of genes that helped to enhance seedling growth.

The 2014 results could offer a huge benefit to Ontario farmers now planting corn, said Swanton, who is calling for more research to be conducted in this area.

“Agriculture is a high-risk business, and these findings could help to reduce the risk to farmers,” he said.

“In terms of pure chemistry, there are some very significant benefits to farmers. We generally think about seed treatments solely for protection, but thiamethoxam could be used to help protect crop seedlings from stresses.”

The researchers began by studying crop reaction to weeds. They found that developing plants could detect light from below the soil surface. Changes in light, such as those caused by weeds growing nearby, delayed seed germination. Normally that would mean a delay in seedling emergence, which could lead to an uneven crop stand.

“These plants are like computer network boards, and they can read what is above the surface,” said Swanton.

“Before we started the study, I had a hard time believing that a seed treatment could trigger genes that could help the crop seedling overcome environmental stresses.”

The researchers found that using thiamethoxam overrode whatever told the seeds to delay germination.

Swanton said the findings are important some studies have found that bees and other pollinators can be adversely affected by this family of pesticides.

“The reality is that farmers are anxious to protect the environment and the bee population,” he said.

“Treating the seeds, rather than applying a pesticide as a broadcast application, should in theory, have a smaller environmental impact. We need research to address the environmental issues.”

The researchers continue to study how plants communicate and how to manipulate gene expression.

The studies, which were partially funded by the Natural Science and Engineering Research Council of Canada, Syngenta Crop Protection, were published in the journal Pest Management Science.