Changing the color of commonly used agricultural netting reduces insect damage in Kujo leek fields

Red netting is more effective at repelling a common agricultural pest than traditional black or white netting, a new study suggests. Researchers experimented with the effect of red, white, black and combination color netting to deter onion thrips from eating Kujo leeks, also known as Welsh onions. In laboratory and field tests, red nets were significantly more effective than other colors at deterring insects.

Additionally, in field trials, onion crops partially or fully covered with red netting required 25 to 50 percent less insecticide than was needed for a completely uncovered field. Changing agricultural nets from black or white to red could help reduce pesticide use and the negative impact it can have on the environment, while supporting more sustainable and efficient agricultural practices.

The results of this search appear in Scientific reports.

Pests can be a nightmare for any gardener. No sooner do fresh buds appear than they are covered with aphids, beetles and other insects looking for a delicious snack. While synthetic insecticides are widely used to control pests in gardens and on agricultural crops, many are known to cause damage to the natural environment by leaching into soil and water supplies, and poisoning plants, wildlife and harmless insects. Some pests are also becoming resistant to chemicals, so farmers no longer have options for which products to use and must apply them more often.

Agricultural screens are another way to protect crops and reduce the use of insecticides. You may see the typical white, black or blue greenhouses when you pass an orchard or vegetable field. Like a mosquito net over a bed, they physically prevent insects from accessing crops.

It is logical to think that the most important characteristic of these nets would be the size of the holes in the meshes. The smaller the hole, the smaller the insect must be to enter. However, a research team from the Kyoto Prefectural Agriculture, Forestry and Fisheries Center and the University of Tokyo found that the color of the net could have an even greater deterrent effect.

“We tested red nets whose mesh size was larger than the insect’s body, but which were nevertheless more effective than other classic black or white nets with a smaller mesh size. This “optical pest control” s “Relies on the nature of the insect’s color vision to detect insects. ward off pests,” explained Professor Masami Shimoda of the Graduate School of Agriculture and Life Sciences at the University of Tokyo . “Most insects do not have red photoreceptors in their eyes and it is difficult for them to see the color red. So we found it curious that an invisible color could be used to control them.”

The team focused on one pest, the onion thrips (Thrips tabaci). This insect is highly resistant to insecticides and causes considerable damage to a range of important crops around the world, eating them and spreading harmful viruses. The researchers tested three color combinations of red mesh (red-white, red-black and red-red) at three mesh sizes (2 millimeters, 1 mm and 0.8 mm). They also tested typical black, white and black-white combination nets of the same sizes, in the laboratory and in the field.

Overall, all nets containing red fibers performed much better at preventing onion thrips entry than black or white nets. In the second outdoor trial, researchers tested the effectiveness of red-red netting at different coverage levels: no coverage, full coverage, top only, and side only.

Due to an outbreak of onion thrips in the area, an insecticide was used. The fully covered plot required the least amount of insecticide and produced onions of high commercial value. Plots covered only on the ceiling or sides required additional insecticide application, compared to the fully covered plot. Compared to the fully uncovered plot, the red net plots overall reduced the number of insecticide applications needed by 25 to 50 percent.

“These new red nets are more expensive than pesticides, but they are economical because they can be used for years. They are also very effective in controlling pests without all the work involved in spraying pesticides,” Shimoda said . “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 would have the same effect on pests. Hopefully this would reduce manufacturing costs and that we could find ways to increase sustainability.

In addition to reducing onion thrips infestation, another advantage of red netting is that, because it depends on color and not mesh size, it can have larger holes. This improves breathability, reduces the risk of fungal infections and improves access to sunlight. Additionally, with better air circulation, temperatures do not get as high in the greenhouse, making it easier for farmers to work inside.

“If consumers become interested in this type of sustainable agriculture and use less chemical pesticides, I have no doubt that this simple but effective solution will become widespread,” Shimoda said. “My family has been full-time farmers since the Edo period (17th century) and I myself enjoy growing vegetables and fruits on a small scale, although pests can make it difficult. Growing your own fruits and vegetables and eating them fresh is exceptionally worthwhile.”