Researchers at the University of California San Diego and Case Western Reserve University have developed a technology that could target pesticides to treat spots within the soil. A biological nanoparticle, a plant virus, can deliver pesticide molecules deeper below the ground, to places that are normally not within reach. This can make the pesticides more effective at controlling infestations while limiting the toxic that they release to the environment.

This development could help farmers better in managing difficult pests like parasitic nematodes that destroy plant roots deep in the soil, and this could be done with less pesticide. This work was published May 20 in the journal Nature Nanotechnology.

"It sounds counterintuitive that we can use a plant virus to treat plant health," said Nicole Steinmetz, a professor of nanoengineering at the UC San Diego Jacobs School of Engineering and senior author of the study.

"This is an emerging field of research in nanotechnology showing that we can use plant viruses as pesticide delivery systems. It's similar to how we're using nanoparticles in medicine to target drugs towards sites of disease and reduce their side effects in patients."

Pesticides have very sticky molecules when applied, Steinmetz explained. They bind to the organic matter in the soil strongly, making it difficult to get enough to go deep down into the root level where some pests like the nematodes reside and cause severe damage.

To be able to solve the problem, most farmers end up using large amounts of pesticides, which cause harmful residues to build up in the soil and mix into groundwater.

Steinmetz and her team of researchers are working to solve this problem. In a new study, they found out that a particular plant virus, Tobacco mild green mosaic virus, can move small amounts of pesticides deep through the soil easily.

Her team also created a computational model that can be used to know how different pesticide nanocarriers behave in the soil and how deep they can go. It can also predict how much of them is needed to be applied to the soil and how long they will take to release the pesticide.

"Researchers working with a different plant virus or nanomaterial could use our model to determine how well their particle would work as a pesticide delivery agent," said first author Paul Chariou, a bioengineering Ph.D. student in Steinmetz's lab at UC San Diego.

"It also cuts down on experimental workload," Chariou said.

Testing just one nanoparticle for this study involves running hundreds of assays, collecting all the fractions from each column and analyzing them.

"This all takes at least one month. But with the model, it only took us about 10 soil columns and 4 days to test a new nanoparticle," he said.