No gardener or farmer wants to have their crops infested by insect pests. 

Just when it starts to bloom–fresh buds and all–the plants are all covered in aphids, beetles, and other bugs looking for a quick snack. 

Such a devastation makes it understandable seeing the widespread use of synthetic insecticides. We’ve seen people use them to control pests on agricultural crops; sometimes in regular gardens, too.

But as we know, many of those pesticides have caused damage to the environment. They seep into the soil and water supplies, poisoning wildlife, plants, and the helpful insects. 

And to make it much worse, some pests have become resistant to the chemicals. And as the time goes, farmers are either running out of options or needing to apply the pesticides more often.

Some farmers have used agricultural nets to protect crops and reduce insecticides. Typically, the nets are blue, white, or black in color–we usually see them in an orchard or a vegetable field. 

These nets work like a mosquito net over a bed, which prevents them physically from getting to us. The smaller the hole is, the harder it is for the insects to come in. 

However, new research finds that it’s not only just the size of the hole, but also the color. In fact, the color may act as a better deterrent. 

The research team is from the Kyoto Prefectural Agriculture, Forestry and Fisheries Center and the University of Tokyo.

“We tested red nets which had a mesh size that was larger than the insect body, but still more effective than other conventional black or white nets with a smaller mesh size. This ‘optical pest control’ relies on the nature of insect color vision to keep pests away,” said one of the researchers, Professor Masami Shimoda.

“Most insects don’t 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 can be used to control them,” Professor Shimoda continued.

No reds for the wicked pests

In the research, the team focused on one pest, Thrips tabaci, or also known as the onion thrips. 

The insect is highly resistant to insecticides and it wreaks havoc to a range of important crops worldwide. It destroys the plants by eating them and spreading harmful viruses.

On the insect, the researchers tested three color combinations of red nets: red-white, red-black and red-red. The nets also came in three different mesh sizes, at 2 mm, 1 mm, and 0.8 mm).

Moreover, the team also tested the typical color combinations on nets of the same sizes. They tested the nets both in the lab and in the field.

The team found that all nets with red colors had significantly better performance at keeping onion thrips away from the crops. 

To test their hypothesis better, the team did a second outdoor trial. Here, they wanted to find out the effectiveness of red-red nets at different levels of cover.

The different levels of cover include no cover, full cover, top only, and side only.

Unfortunately, due to an outbreak of onion thrips in the area at the time of experiment, the team had to use insecticide.

However, they found that the fully covered plot didn’t need a lot of insecticide. It also produced onions of high commercial value. 

Plots that were covered only partially needed more application of insecticide. 

But overall, compared to the completely uncovered plot, the red-netted ons reduced insecticide applications. The number of the reduction may reach 25% to 50%.

Professor Shinoda explained, “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.

“My dream is that in 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. Hopefully, this would reduce manufacturing costs, and we can find ways to increase durability.”

 

 

Another plus point

Other than repelling onion thrips naturally, another plus point of red nets is the reliance of color. With it, farmers won’t need to be concerned about smaller mesh holes. 

In fact, they can opt for the larger-holed ones. That way, farmers can relax about net breathability. 

Red nets reduce the chance of fungal infections, and they give crops more access to sunlight. Also, since larger holes lead to better airflow, temperatures won’t become too high when placed in a greenhouse. Farmers could work more comfortably inside.

Professor Shimoda added, “If consumers are interested in this type of sustainable agriculture and using less chemical pesticides, I have no doubt that this simple yet effective solution will spread widely.

“My family have 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 challenging. Growing your own fruits and vegetables and eating them fresh is exceptionally worthwhile”

Now, one thing to note from this research is that the team experimented on one type of pest only. It’s unclear whether red nets will work on any other kinds of insect pests. 

Hopefully, the team (or other research team)  plans to do further research on the color’s effectiveness on other insect pests.

But in the meantime, maybe we can combat other insect pests with a newfound worm species that infects and kills insects.

Insect killing tiny worms

“How could a tiny worm infect and kill insects?”

That was also my question when I first read about this, but that’s what scientists at UC Riverside have discovered.

The worms, called nematodes, could help control crop pests in warm, humid places. 

Now, there are other nematodes, and they’ve been around. However, they don’t usually live well in humid and warm climates.

This new species is a member of a family of nematodes called Steinernema. They were first discovered in the 1920s.

UCR nematology professor Adler Dillman, whose lab made the discovery, explained, “We spray trillions of them on crops every year, and they’re easy to buy.

“Though there are more than 100 species of Steinernema, we’re always on the lookout for new ones because each has unique features. Some might be better in certain climates or with certain insects.”

In order to get a better understanding of a different species of steinernema, Dillman’s laboratory requested more samples. The samples were obtained from Thailand.

“We did DNA analysis on the samples and realized they weren’t the ones we had requested. Genetically, they didn’t look like anything else that has ever been described,” Dillman said.

The newfound species are almost invisible to the naked eye. They’re just around half the width of a human hair, and just under 1mm long. When we see them in a flask, which may contain several thousand of them, it just looks like murky  water.

The researchers have named the new species Steinernema adamsi. They’re honoring the American biologist Byron Adams who has refined the understanding of nematode species.

Minuscule worms

As an undergraduate, Dillman was fascinated about the worms’ life cycles.

As juveniles, nematodes live in the soil with sealed mouths–in a state of arrested development.

In that stage, the worms wander around looking for insects to infect. When they find a victim, they enter its mouth or anus, then they defecate highly pathogenic bacteria.

“A parasite that poops out pathogenic stuff to help kill its host, that’s unusual right out of the gate. It’s like something out of a James Cameron movie,” Dillman said. 

After the infection, the insect dies within 48 hours. 

Dillman added, “It essentially liquefies the insect, then you’re left with a bag that used to be its body. You might have 10 or 15 nematodes in a host, and 10 days later you have 80,000 new individuals in the soil looking for new insects to infect.”

When it comes to efficacy, the researchers are sure that S. adamsi kills insects. 

They’re certain because they put some of the worms in containers with wax moths. The worms, though not many, killed the moths in two days.

In the future, the researchers want to find out other abilities or properties that S. adamsi have. Because as of now, they’re unsure if the worm can resist UV light, dryness, or extreme heat. They also don’t know the range of insects that the worm can infect.

Nevertheless, the researchers are confident that the newly found worm species will be beneficial on some level. 

Dillman, who remained optimistic about the worm’ potentials, said, “This is exciting because the discovery adds another insect-killer that could teach us new and interesting biology.

“Also they’re from a warm, humid climate that could make them a good parasite of insects in environments where currently, commercially available orchard nematodes have been unable to flourish.”

 

Sources:

https://www.sciencedaily.com/releases/2024/02/240214122640.htm

https://www.sciencedaily.com/releases/2024/02/240208121947.htm