Different Pest Attacks Change Plant Defenses; Understanding Them Helps Agriculture 

Farmers have to deal with pests all the time, and while the use of pesticide can be a polarizing subject now, understanding pest attacks may help them in the future. 

New research has found that the time when insects attack a plant can change its defenses and nutritional quality. In this case, it’s weevils. 

Aphids have been the one troubling pea plant farmers because of its virus carrying characteristics, but it’s not just them. The new research discovered that weevils that only takes tiny bites have played a significant role in plant health. 

Depending on what the weevils eat before or after, aphids can increase or decrease the plant’s ability to fight the virus. 

Many studies have focused on a single pest and its impacts. This study is the one of the few to look at the interaction of several antagonists: aphids, weevils, and a virus. 

Lead author Saumik Basu said, “Plants in the field have a chance of being exposed to many different types of biotic stress elements, what we call antagonists. 

“Based on how these antagonists are coming to the plants, that can change the plant responses and ultimately leads to changes in their overall productivity.” 

Through a set of greenhouse experiments, Basu and colleagues attempted to understand what happens to the pea plant fields of Eastern Washington’s Palouse area. 

What they found was that plants face different attacks from pea leaf weevils, Sitona lineatus, and pea aphids, Acrythosiphon pisum, plus a pathogen that the pea aphids carry called Pea enation mosaic virus, or PEMV. 

Little weevils 

The researchers experimented. First, they let weevils feast on the plants then the aphids, and then they reversed the order. Moreover, they included scenarios where the plants were infected with the virus and some where they did not as well as a control group. 

After letting the plants be attacked, the researchers removed the pests and they let the plants grow for a week. Then, they ran a set of analyses to know how the plants reacted, assessing hormone levels, defense genes, and nutritional qualities. 

Apparently, when the weevil feasts first on the pea plants, it enhances some of the plants’ anti-pathogen defense responses, helping them become more resilient to a virus infection. 

But if the weevil gets the second turn after the aphid, the plants lose their anti-pathogen defense responses, making the virus spread more easily. In turn, virus-infected plants had stronger anti-herbivore responses, putting out compounds that interfere with the plant-eating pests. 

Weevil enhancing plants defenses is not good news, though. Because, the study found that when that happens, it lowered the nutrition of the plant by reducing the plants’ available amino acids. 

“If we know beforehand when these interactions are happening, that information gives farmers a best possible remedy to prevent their fields from the attack. This kind of information is really important for designing sustainable pest and pathogen management strategies,” said Basu. 

And in the end, understanding plant responses as well as these complex relationships may help agriculture in the future. 

Basu said, “In a natural environment, a plant is exposed to different types of organisms, not just one or two, but many. The order and the complexity — how many there are, what different types there are and their interactions — affect how the plant responds to all these attackers.” 

 

Farmers don’t know that their seeds are pesticide-coated 

Now, it’s understandable that farmers want to use pesticide. Scientists have been trying to solve pest problems so that we may use it less.  

But new research finds that farmers don’t know they’re using pesticide-coated seeds like neonicotinoids, which are highly toxic to both pest and beneficial insects. 

These seeds are getting more frequent but are underreported because the farmers don’t know it. While it may sound good to the farmers, this lack of data may complicate efforts to evaluate the value of different pest management strategies, while also protecting human health and the environment. 

One of the researchers Paul Esker said, “We reviewed existing evidence, as well as proprietary and novel government data, on seed treatment usage and found that many farmers either did not know what pesticides were on their seeds or falsely assumed that seed treatments did not include certain pesticides. 

“This lack of knowledge could lead to overuse of pesticides, which could harm the environment and farmers’ health.” 

Asking the farmers 

The team analyzed data from Kynetec, a third-party global marketing and research firm that maintains one of the most comprehensive datasets on pesticide use in the United States. 

They found that the use of seed treatments in the U.S. grew over the past decade, particularly in corn and soybean production.  

In the 2012 to 2014 period, 90% of corn acres and 76% of soybean acres were grown with treated seeds. Of the insecticides applied to seeds, neonicotinoids accounted for roughly 80%. 

Then, they analyzed farmers’ responses. Around 98% of farmers were able to provide the names of the field-applied pesticides used on their cotton, corn, wheat or soybean crops. 

However, only 84% of cotton growers, 65% of corn growers, 62% of soybean growers, 57% of winter wheat growers and 43% of spring wheat growers could provide the name of the seed-treatment product on their crops. The rest either did not answer the survey question or specified that they did not know. 

Another researcher involved in this study Margaret Douglas said, “One of the most important findings of this study is that farmers know less about pesticides applied to their seeds than pesticides applied in other ways. 

“This is likely because seed is often sold with a ‘default’ treatment that contains a mix of different pesticide active ingredients, and the treated seed is exempt from some labeling requirements.  

Lead author Claudia Hitai stated that the lack of information on the use of pesticidal seed treatments means that a large amount of pesticide used is not captured in existing pesticide-use datasets. 

“Reliable data on pesticide use is needed by regulators, farmers, and researchers to increase agricultural production and profitability and to protect human health and the environment from the adverse effects of pesticides,” said Hitai. 

The importance of information 

In the end, the research team concluded that farmers, researchers and regulators could benefit from improved labelling of pesticide-treated seeds. There should also be information about the active ingredients contained in treated seed products on public websites. 

Researchers also found it vital to get data about the planting location of treated seeds in order to help assess pest resistance and the local effects of pesticides on the environment. 

Esker said, “The lack of knowledge by farmers about the pesticides applied to seed is an example of why it is important to maintain a strong university extension system that can provide up-to-date information about different seed treatments, what these treatments do, and what the empirical data shows. 

“This is also an opportunity for further collaboration among different disciplines, like agronomy, plant pathology, entomology, economics and environmental science, to address farm issues from a whole-system perspective.” 

 

Sources

https://www.sciencedaily.com/releases/2021/08/210810104646.htm  

https://www.sciencedaily.com/releases/2020/03/200317215632.htm  

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