Researchers at North Carolina State University created "Plant Armor," a textile that forces insects to navigate a maze-like path if they try to reach a plant. In multiple experiments, the design outperformed an alternative crop cover in terms of preventing insects from reaching cabbage plants.
Findings of Research:
According to their findings, Plant Armor could provide a more effective, chemical-free alternative for insect protection.
"We discovered that we can use this new technology to protect against insects that we didn't think we could protect against," said Grayson Cave, a doctoral candidate at NC State. "We've demonstrated that we can use a mechanical barrier to protect against tobacco thrips and possibly other insects while still allowing the plant to grow and thrive beneath."
Previously, plant covers were designed to exclude insects based solely on size – similar to a window screen, according to the researchers. That strategy, however, can be problematic when attempting to keep out insects as small as tobacco thrips, which are about the size of a pencil point.
"To exclude insects that are really small using traditional textile cover designs, the openings would have to be so small that it also prevents water, air, and moisture from penetrating," said study senior researcher Mike Roe, William Neal Reynolds Distinguished Professor of Entomology at NC State. "We had to devise a method of excluding the insects that were not solely based on pore size."
To that end, the researchers created a three-layer, three-dimensional cover knitted in the outermost and innermost layers with clear yarn. The yarn, which can be made from recycled plastic, allows sunlight to pass through while keeping insects away from plants. Within the Plant Armor, a knitted inner layer is sandwiched perpendicular to the two surrounding layers, forming a maze-like structure.
"With our design, the insect must figure out how to navigate the maze to reach the plant on the other side," Roe explained. "It's more difficult to get through because of the tortuosity. The insect has a limited amount of time to find food before it dies. For a young insect, that is a relatively short period of time."
In the first of three experiments, researchers discovered that insects took significantly longer to penetrate the Plant Armor. They separated a cabbage leaf and ten tobacco thrips in a Petri dish using Plant Armor or another crop cover. Five of the thrips took about three hours to get through the Plant Armor, whereas it took only 12 minutes for them to cross a commercially available, single-layer crop cover. In the same experiment with young, unfed caterpillars, their design prevented unfed young caterpillars from crossing the Plant Armor in 12 hours.
"In real life, the insect has many other options for where to go to find food; this was a worst-case scenario where they only had one option," Roe explained. "As a result, we anticipate that protection in the natural environment will be much greater."
When researchers tested how well they could protect potted cabbage plants inside a cage with unfed caterpillars, uncovered plants were infested and almost completely eaten, whereas Plant Armor-protected plants were not. After 10 days, they had not found a single caterpillar on the covered plants.
Their most recent experiment was a three-month outdoor field trial to see how well the Plant Armor worked as a greenhouse cover. The researchers discovered that plants protected by Plant Armor grew larger on average; the weight of cabbages protected by Plant Armor was nearly three times that of the control.
More research is needed to determine whether the inner layer's thickness, pore size, or maze-like structure successfully excluded insects. Their work, on the other hand, shows that their chemical-free design can be effective against tiny critters.
Researchers believe their crop cover could be a viable option for high-value crops such as grapes. They also want to investigate whether the cover could be used to help protect plants in extreme conditions – and as the climate changes.
"Part of what we're doing is finding new, smart textiles," said Andre West, associate professor of textile, apparel, and technology management at NC State and director of Zeis Textiles Extension. "We believe that this design could benefit farmers in harsh environments or where crop production is limited in specific areas. It may also be an option for organic farmers. Not only is the product made from recycled materials, but it also has the potential to be recycled again."
(Source: North Carolina State University)
