This article contains excerpts from an interview that first aired on Agriscience Explained™ in January 2025. Hosted by Tim Hammerich, this episode focused on Invisible Pest Management and featured interviews with Michael Logoluso, a raisin grower in California, and Dr. Tim Thoden, a nematologist who works at Corteva.
Farming is a business, and profit is never guaranteed. To manage risk and give the crop the best possible chance of success, farmers rely on the latest in management practices and some cutting-edge science.
Nematodes are the most abundant multicellular organisms on the planet, but often they go completely unnoticed because they can't be seen without a microscope. What we most often see in agriculture is their effects on our crop.
Whether you grow soybeans, vegetables or grapes, it's important to know your nematodes. Michael Logoluso has seen the impacts of nematodes for the past three decades working in the raisin grape business in California. He's a farm manager for a large grower and packer of California raisins.
Nematodes are a serious pest not only in raisins, but also in a wide variety of crops. But because we can't see these microscopic worms with the naked eye, they largely go undetected.
“The big thing is a lot of growers are focused on so many other aspects of trying to get that crop to market that they don’t consider that nematodes may be causing the problem. And I can't stress enough that you need to go out there and do a soil sample,” Logoluso says.
So let's dive deeper into this mysterious and, in many ways, fascinating world of nematodes. How are they causing so much damage to our crops, and what can farmers do about it? What are the latest tools and technologies out there being developed, and how can they help?
Corteva nematologist Dr. Tim Thoden states that these nematodes are creating serious impacts economically and agronomically on crops every year.
“It is believed that the damage that nematodes globally do is around $120 billion to $150 billion US dollars per year…It's a huge economic damage. From research and studies, it is believed that nematodes roughly take away 15% to 20% of global yield potential. So that is kind of the financial and the real-world impact that nematodes can have,” Thoden says.
The biggest impact is from nematodes that feed on plants and show up in our crops as pests.
“I think the most important, probably by far, is root-knot nematodes that you'll find with dozens of individual species, infecting almost every crop that is of importance,” Thoden notes.
The root-knot nematode is still the biggest nematode problem at Lion Farms in California, where Logoluso works. Even though he has been aware of the problem for a long time, and he samples his soil regularly, the nematode problem still has a way of getting out of hand.
There was a time when farmers would fumigate a field using methyl bromide to get rid of all the nematodes before planting, but that treatment was phased out by 2005, and farmers plagued with nematode pressure had to look elsewhere for answers.
Those alternatives include a limited number of tools in the toolbox, both old and new. To take more of an integrated approach to nematode pest management, Logoluso says they started appreciating that healthy soils are an essential base layer to managing these nematodes.
“We realized it couldn't just focus on chemicals. We started to focus more on our soil conditions, how we can improve soil fertility, how we could help the biodiversity in our soil, and start focusing on healthy soil,” Logoluso says.
Things like crop rotation and building soil suppressiveness through soil health can be really helpful, especially combined with tools like resistant rootstocks. But in a lot of cases, it's still just not enough to manage plant parasitic nematodes on its own. More tools are still required. This farmer need sent Thoden and his colleagues at Corteva on a journey to develop a modern, novel selective nematicide called ReklemelTM active.
Farmers like Logoluso have welcomed the chance to give Reklemel a try on their farms, which is sold under the name Salibro® nematicide. At Lion Farms, they're in their third year of Salibro trials and are looking forward to analyzing the data on the impact it has made.
And Thoden says the work doesn't stop there.
“We are still investing in finding novel chemistry approaches,” he says. "We're still looking for novel chemistries that fit into a concept of managing well the pest but being safe to the environment and having a good sustainability footprint,” Thoden noted.
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