Plant parasitic nematodes are tiny organisms that live in the soil and cause damage to crops by feeding on their roots. Currently, farmers eliminate nematodes by applying pesticides to their crops. Since these chemicals are meant to sit only on the soil surface, they must be applied in large quantities, often with large amounts of water to flush them down to the roots. This means farmers have to spend a lot of money on pesticides, a lot of water has to be used, and a lot of toxic chemicals get into the environment.

When nematodes feed on plant roots, they hinder the plant's ability to absorb water and nutrients from the soil

Now, using a modified plant virus, scientists have developed a greener and more effective way to eliminate nematodes.

Looking for a less wasteful, more environmentally friendly alternative, Professor Nicole Steinmetz of the University of California, San Diego, and her colleagues turned to the Tobacco Green Mosaic Virus. Unlike pesticides, Tobacco Green Mosaic Virus is naturally good at spreading downward through the soil.

Engineers have developed nanoparticles made from plant viruses that can deliver pesticide molecules deep into the soil that were previously unreachable. This development has the potential to help farmers effectively control parasitic nematodes that plague crop roots while minimizing costs, pesticide use and environmental toxicity.

The scientists first remove the virus's RNA, making it non-infectious to plants. Nanoparticles of the modified virus were then mixed into a solution containing the pesticide ivermectin. The insecticide is encapsulated in nanoparticles through a simple process of "thermal shape switching" that heats the mixture.

Microscope image of nanoparticles/University of California, San Diego, USA

In laboratory tests, the pesticide-laden nanoparticles successfully penetrated 10 centimeters (3.9 inches) of soil. When these particles were recovered from soil samples and added to petri dishes filled with nematodes, the pesticide they carried wiped out at least half of the nematode population.

This one-shot synthesis method has several advantages. First, it is low cost, requires only a few steps, and the purification process is simple. This method is more scalable, paving the way for farmers to obtain more affordable products. Second, this method simply encapsulates the pesticide within nanoparticles rather than chemically binding it to the surface, thus preserving the original chemical structure of the pesticide.

The plan now is to test the nanoparticles on actual crop plants infested with nematodes. "This technology has the potential to improve field treatments without increasing pesticide use," Steinmetz said.

A paper on the research was recently published in the journal NanoLetters.