Maze-like material keeps even the smallest insects from reaching crops

Instead of using insecticides, farmers will sometimes cover their plants with a mesh fabric. A new such material has now been developed, which keeps out a wider range of bugs while still allowing crops to get enough sunlight and water.

With all crop-cover materials, the size of the gaps in the mesh determines the size of the pests that are kept out. Unfortunately, tiny insects like tobacco thrips are small enough that they can simply pass through the gaps in existing products. If the gaps were made small enough to stop the thrips, then not enough air, water or sunlight would be able to reach the plants.

Seeking a more effective alternative, scientists at North Carolina State University have developed an experimental “Plant Armor.” It consists of three knitted layers.

On the outside and the inside are layers made of transparent plastic yarn. Sandwiched between them is another knitted layer, the fibers of which run perpendicular to those of the other two layers. The idea is that even if insects are small enough to make their past the surface of the material, its maze-like internal structure will make it very difficult for them to get all the way through.

In one lab test, groups of 10 thrips were placed in a Petri dish along with a cabbage leaf that was protected by either a piece of Plant Armor or an existing crop cover material. It was found that the insects took three hours to get through the Plant Armor, whereas they got through the other product in just 12 minutes.

In another test, both Plant-Armor-covered and unprotected potted cabbage plants were placed in a cage along with unfed caterpillars. The unprotected plants were quickly infested and almost completely eaten, while no caterpillars were found on the protected plants, even after 10 days.

Finally, when cabbage plants were grown in a field either covered or uncovered, the covered plants were on average three time larger and heavier after a three-month growth period.

Importantly, because the Plant Armor doesn’t simply rely on small gap size, sufficient amounts of water, air and light are still able to pass through. Additionally, doctoral candidate Grayson Cave (first author of the study) told us that the material is not only reusable, but it can also be made from recycled materials.

“We found it’s possible to use this new technology to protect against insects we didn’t think we could protect against,” he said. “We’ve shown we can use a mechanical barrier that will protect against tobacco thrips and possibly other insects, allowing the plant to grow and thrive underneath.”

The research is described in a paper that was recently published in the journal Agriculture.

Source: North Carolina State University

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