The type of Welsh onions used in the experiment were a variety called Kujo negi. These onions are a traditional vegetable of the Kyoto region and a staple part of local cooking. Credit: 2024 Tokumaru et al./Scientific Reports
Key points:
- Nets with red fibers are better at preventing onion thrips from eating Kujo leeks than black or white nets.
- Agriculture plots that are covered by red nets require 25-50% fewer insecticide applications.
- Red nets rely on color and not mesh size to protect plants and can have larger holes that improve breathability, reduce the chance of fungal infections, and improve access to sunlight.
Red nets are better at deterring common agricultural insect pests than typical black or white nets. A new study, published in Scientific Reports, explains how changing agricultural nets can help reduce pesticide use and the related negative environmental impact.
Agricultural nets can be used to physically prevent insects form getting to crops, which helps reduce insecticide use and its associated damaging environmental effects. In the current study, researchers tested three color combinations of red nets (red-white, red-black, and red-red) at three mesh sizes (2 millimeters, 1 mm, and 0.8 mm). They also tested black, white, and black-white combination nets of the same sizes. All tests occurred both in the lab and in Kujo leek fields.
The research team focused on the onion thrips (Thrips tabaci) as it is highly resistant to insecticides and causes extensive damage to a range of important crops worldwide. They found that all nets that included red fibers were significantly better at keeping out onion thrips than black or white nets.
In a second outdoor trial, the researchers tested the effectiveness of red-red netting at different levels of cover – no cover, full cover, top only, and side only. The team also used insecticide because of an outbreak of onion thrips in the area. They found that the fully covered plot required the least amount of insecticide, while the plots that had ceiling or side cover required an additional application of insecticide. Compared to the uncovered plot, the red-netted plots reduced the number of insecticide applications by 25-50%.
Researchers determined that red nets could have larger holes because they rely on color and not mesh size. Larger holes improve breathability, reduce the chance of fungal infections, and improve access to sunlight. Additionally, with improved airflow, it is easier for farmers to work inside.
“My dream is that in the future we can make red nets that don’t look red – at least not to the human eye, but they would have the same effect on pests,” explained Masami Shimoda, professor at the University of Tokyo. “Hopefully this would reduce manufacturing costs, and we can find ways to increase durability.”