If insects want to approach a plant, they are forced to negotiate a maze-like path developed by North Carolina State University researchers. In comparison to an alternate crop cover, the design was more effective at preventing insects from reaching cabbage plants in repeated experiments. The Plant Armor, according to the researchers, could provide a more effective, chemical-free alternative for pest protection. “We discovered that we can use this new technology to guard against insects we didn’t think we could protect against,” said Grayson Cave, a doctorate candidate at NC State and the study’s first author.
“We’ve demonstrated that we can employ a mechanical barrier to keep tobacco thrips and probably other insects out while allowing the plant to grow and thrive underneath.” Previously, plant covers were meant to keep insects out only based on their size, much like a window screen, according to researchers. However, that method can be challenging for trying to keep out insects as little as tobacco thrips, which are approximately the size of a pencil point. “To exclude truly minute insects using typical textile cover designs, the gaps would have to be so small that water, air, and moisture couldn’t get through,” said study senior researcher Mike Roe, William Neal Reynolds Distinguished Professor of Entomology at NC State.
The researchers achieved this by creating a three-layer, three-dimensional cover crocheted with clear yarn in the outermost and innermost layers. The yarn, which may be manufactured out of recycled plastic, allows light to travel through while keeping insects away from plants. Within the Plant Armor, a knitted inner layer is layered perpendicular to the two outer layers, forming a maze-like structure.
“The insect has to figure out how to pass through the maze to get to the plant on the other side with our design,” Roe explained. “It’s more difficult to get through because of the tortuosity. The bug only has a limited amount of time to find nourishment before it dies. For a juvenile insect, that is a relatively short period of time.”
In the first of three tests, researchers discovered that insects took substantially longer to penetrate the Plant Armor. They used Plant Armor or another crop cover to separate a cabbage leaf and ten tobacco thrips in a Petri dish. Five thrips required three hours to get through the Plant Armor, but only 12 minutes to get through a commercially available single-layer crop cover. Their approach was over 90% efficient in stopping unfed juvenile caterpillars from passing the Plant Armor in 12 hours in the identical trial with young, unfed caterpillars.
“In real life, the insect has a number of options for finding food; this was a worst-case scenario where they just had one option,” Roe explained. “As a result, we anticipate significantly stronger protection in the natural environment.” When scientists examined how successfully Plant Armor could protect potted cabbage plants in a cage containing unfed caterpillars, they found that unprotected plants were infested and nearly totally eaten, but plants that were covered and sealed with Plant Armor were not. After 10 days, they found no caterpillars on the covered plants.
The Plant Armor’s most recent experiment was a three-month outside field trial to see how well it operated as a greenhouse cover. Plants protected by Plant Armor were found to be larger on average; the weight of cabbages protected by Plant Armor was nearly three times that of the control. More research is needed to evaluate whether the thickness, pore size, or maze-like shape of the inner layer successfully excluded insects. However, their research shows that their chemical-free design can be effective against small animals. “Thrips are minuscule,” Cave explained. “We believe we have a fair chance of keeping other, larger insects out if we can keep them out. The neonatal caterpillars, on the other hand, must feed right away because they are the tiniest stage of caterpillars. This provides some preliminary evidence that this could be protective against other caterpillars as well.” Researchers believe their crop cover could be a viable option for high-value crops such as grapes. They also want to see if the cover may be used to assist protect plants in extreme weather and as the climate changes in the future.
Andre West, associate professor of textile, apparel, and technology management at NC State and director of Zeis Textiles Extension, stated, “Part of what we’re doing is identifying new, smart textiles.” “We believe that this design could benefit farmers in harsh regions or in areas where crop output is restricted. For organic farms, it might also be a viable option. Not only is the product manufactured using recycled components, but it also has the potential to be recycled again.” The research was published in the journal Agriculture under the title “Novel 3-D Spacer Textiles to Protect Crops from Insect-Infestation and Enhance Plant Growth.” Marian G. McCord, senior vice provost at the University of New Hampshire and adjunct professor in NC State’s Department of Forest Biomaterials; Bryan Koene and Benjamin Beck of Luna Innovations; and Jean M. Deguenon and Kun Luan, postdoctoral research scholars at NC State, are among the co-authors.
This study is based on research funded by the United States Department of Agriculture’s National Institute of Food and Agriculture under Agreement No. 2015-33610-23785 of the Small Business Innovation Research Grants Program. Any opinions, results, conclusions, or recommendations stated in this article are solely those of the author(s) and do not necessarily reflect the views of the USDA. Cave received a teaching assistantship from NC State, while Cave and Roe are funded by the North Carolina Agricultural Experiment Station. Potential conflicts of interest: Vector Textiles is the sole owner of a patent related to Plant Armor technology. McCord, Roe, and West are co-inventors on a patent linked to NC State’s invention, and would benefit from any cash generated from commercialization.