Nematodes, also known as roundworms, are the most abundant animals on earth but are largely misunderstood. In gardening and agriculture, several nematode species are known for being pests, but it’s important to recognize that many other nematode species are beneficial, providing biological control of insect pests. To explain how lab-produced pheromones can be used to repel pest nematodes and stimulate beneficial nematodes, my guest this week is Dr. Fatma Kaplan, the CEO and founder of Pheronym.
Fatma wants to spread the word that not all nematodes are bad. It’s a common misconception that nematodes are universally pests, but the truth is, some soil nematodes prey on pest nematodes and the larvae of pest insects. Based in Davis, California. Fatma studies how pheromones influence nematode behavior and how they can be applied to keep plant-parasitic nematodes from damaging crops or how they can be used to encourage predatory nematodes to get to work destroying pest larvae. These products are not on the commercial market yet, but they have the potential to provide effective, organic alternatives to chemical pesticides.
Fatma’s grandparents were farmers with hazelnut orchards. She’s always been interested in nature. “It’s just part of me,” she says. She won a fellowship to do her graduate studies in the United States and earned a Ph.D. in plant molecular and cellular biology at the University of Florida. She had originally intended to return to her home country but ended up remaining in the United States for postdoctoral studies in identifying communication signals — i.e., pheromones — in microscopic roundworms, AKA nematodes.
Plant-parasitic nematodes were a big problem for agriculture, particularly viniculture. In fact, nematodes nearly wiped out the whole wine industry in her home country.
Fatma saw the potential in identifying the molecules that nematodes produce, and the implications for agriculture. Insect pheromones are already pretty well known and used effectively for pest control in eco-friendly ways, she points out. Because pheromones are species specific, their use won’t harm non-target species. Traps to detect or control a pest insect could be baited with pheromones that attract that species and that species only, sparing beneficial insects from harm. She believed the same concept could be applied to nematodes.
In 2004, Fatma was recruited to identify nematode pheromones. “Scientists were trying to identify these compounds for decades,” she says.
It was a very tough project, she says, though she successfully identified a sex pheromone molecule produced by the roundworm Caenorhabditis elegans. And once identified, the molecule could be synthesized.
The U.S. Department of Agriculture then hired her in 2008 to be the agency’s nematode pheromone expert. It was around the time that methyl bromide, a colorless, odorless fumigant found to deplete the ozone layer and pose a risk to human health, was being phased out. It had been a popular pesticide for controlling fungi, weeds, insects, nematodes and rodents.
“The farmers really needed a solution to control plant-parasitic nematodes,” Fatma recalls. “And I thought, OK, this is the place where I want to be, and I have this great opportunity to bring this new knowledge, turn it into technology, and provide it to farmers.”
While working for the USDA, Fatma was introduced to beneficial nematodes and learned that the beneficial nematodes used the same class of communication signals as plant-parasitic nematodes do.
During her time with the USDA, Fatma did not get to accomplish everything she had set out to do because the agency shrank, and as one of the last hired, she was one of the first to go. Then, working with other scientists, Fatma wrote grant applications and founded Kaplan Schiller Research, which would later evolve into Pheronym. When they received funding, Fatma discovered that product development was very different from performing research. They landed with a business incubator to help them formulate a product concept and conduct R&D from the laboratory to the field.
What’s a Nematode?
Nematodes, or roundworms, are cylindrical, non-segmented organisms that account for four out of every five animals on the planet. About 30,000 unique nematode species have been identified but the total number of nematode species is estimated to exceed 1 million.
Nematodes of different species have various diets: Some eat plants, some eat bacteria, some eat fungi, and some eat other nematodes.
Based on their diets and behaviors, there are species we consider to be pests, such as root-knot nematodes, and others we consider to be beneficial nematodes, such as Heterorhabditis bacteriophora, which prey on beetle larvae. Heterorhabditis bacteriophora don’t eat the larvae directly, but they release a symbiotic bacteria that kills the insect and proliferates, and the nematodes eat the bacteria.
Understanding Nematode Pheromones
Both “good” and “bad” nematodes use the same chemical language, Fatma says. Consider the molecules they produce to be an alphabet. They can tell each other “come over here,” “you should go away” or “no more resources here.”
It was assumed that nematodes deploy pheromones for the same reasons that insects do: as communication signals for mating, alerting others to a food source, raising an alarm, etc.
Fatma identified a mating pheromone that female C. elegans nematodes produce to attract males. She recognized that nematode traps baited with the pheromones could remove the males from the population.
Pheromones that can be used to repel nematodes are known as dispersal pheromones — and they can be very useful to keep parasitic nematodes away from crops. She says all agricultural nematodes are challenging, but particularly the plant-parasitic nematodes.
Nemastim and PheroCoat
Fatma’s company has a product called Nemastim that uses pheromones to tell beneficial nematodes where they can find pest insects and encourages them to eat. Combined with two popular beneficial nematode products, Nemastim targets 28 of the most problematic pest nematodes.
Fatma says over time nematodes lose their instinct to search and attack. Nemastim is designed to trigger that instinct.
Under normal conditions, when a nematode exits an insect that has been consumed, it enters a special stage of its life in which it closes its mouth, develops protection from harsh environments and bad chemicals, and has a limited amount of food reserves, Fatma explains. If it moves constantly, it will run out of reserves and die.
If a nematode does not find a new insect to prey on, it will stop moving. And because nematodes offered for sale may have been stored for weeks and then shipped, they are likely low on reserves and have lost the instinct to move and search. But Nemastim tells them it’s time to get out and hunt again.
“It’s almost like a factory resetting,” Fatma says.
When Fatma read that plant-parasitic nematodes can differentiate between healthy plants and infected plants, she thought this was a sign of chemical communication at work.
Root-knot nematodes are the classic example of plant-parasitic nematodes. They attack plant roots and form a nodule. Once in a nodule, they remain in place.
“If you take the root out of the soil or if the plant dies, they can’t reproduce anymore,” Fatma says. “They are stuck to the plant.”
Since root-knot nematodes are stuck once they commit to a certain plant, they don’t have the option to try out a few plants until they find a healthy one to infect. They must get it right on the first try. So Fatma’s company developed a product that would signal to nematodes that a plant is already infected.
The product, PheroCoat, is a seed treatment that acts as a repellent by telling plant-parasitic nematodes the host plant is already infected.
PheroCoat can be used in combination to trap crops, so the nematodes avoid the treated plants and instead go into the roots of the trap crops, which can later be removed and disposed of to rid the soil of root-knot nematodes.
Neither of these Pheronym products is commercially available yet, but there are readily available beneficial nematode products for gardeners, such as NemaSeek and NemAttack from Arbico Organics.
Beneficial nematodes are usually applied by mixing them with water in a pump sprayer. Fatma notes that if a sprayer has a filter, the filter needs to be removed before applying nematodes.
Beneficial nematodes are often sold in small packages, the size of a Sweet’N Low packet, but once applied to a lawn or garden, their population will increase exponentially. However, Fatma says many studies have found that purchased nematodes do not persist in soil for more than two or three years. “It turns out that they’re predators waiting for the nematodes to eat them,” she says. “So their predators keep them in check.”
Fatma also notes that purchased beneficial nematodes do not harm soil microbiome and are shown to improve soil biodiversity.
When spraying pesticides on insects that live aboveground, gardeners can easily see the effects, Fatma points out. But for pests that live in soil, it’s not easy to tell if beneficial nematodes are working. However, when grass grows back or crops have better survival rates, the results will be clear.
And it behooves me to point out that whenever home gardeners and farmers can replace broad-spectrum pesticides with a biological control such as beneficial nematodes, it’s a great thing.
Beneficial nematodes are also useful for beekeepers, as they can be used to control Galleria mellonella, the greater wax moth, which parasitizes honeybees. Many labs that study infectivity or infection use Galleria as a model organism and teaching tool, Fatma points out.
I hope you enjoyed my conversation with Dr. Fatma Kaplan of Pheronym and learned something new about nematodes and pheromones. If you haven’t listened yet, you can do so now by scrolling to the top of the page and clicking the Play icon in the green bar under the page title.
Have you had trouble or success with nematodes in your garden? Let us know in the comments below.
Links & Resources
Some product links in this guide are affiliate links. See full disclosure below.
Episode 049: When Good Bugs Eat Bad Bugs: The Business of Beneficial Insects
Episode 050: Organic Pest Control: Beneficial Insects and Beyond
Episode 067: Predatory Beneficial Insects: Feared Foes of Garden Pests, Pt. 1
Episode 068: Top Predatory Beneficial Insects and How to Attract Them, Pt. 2
Episode 121: Fire Ant Control: The Down and Dirty on Identification, Behavior and What to Know
Episode 144: Understanding Nematodes: Microscopic Worms, Friend or Foe of Your Garden
Episode 195: Identifying and Controlling Garden Pests Organically
Episode 218: Squash Bugs: How to Manage and Control This Challenging Pest
Episode 219: Troublesome Garden Pests: Organic Control Strategies That Work
Episode 252: The Underappreciated Value of Predatory Beneficial Insects in the Garden
Episode 280: How to Get More Beneficial Insects in Your Garden to Manage Insect Pests Naturally
joegardener blog: Japanese Beetle Prevention and Control
joegardener blog: Squash Vine Borer Prevention & Control
joegardener blog: Squash Bug Prevention & Control
joegardener Online Gardening Academy™: Popular courses on gardening fundamentals; managing pests, diseases & weeds; seed starting and more.
joegardener Online Gardening Academy Master Seed Starting: Everything you need to know to start your own plants from seed — indoors and out.
joegardener Online Gardening Academy Organic Vegetable Gardening: My new premium online course membership opens in 2023. Sign up for the waitlist here.
joegardener Online Gardening Academy Beginning Gardener Fundamentals: Essential principles to know to create a thriving garden.
joegardener Online Gardening Academy Growing Epic Tomatoes: Learn how to grow epic tomatoes with Joe Lamp’l and Craig LeHoullier.
joegardener Online Gardening Academy Master Pests, Diseases & Weeds: Learn the proactive steps to take to manage pests, diseases and weeds for a more successful garden with a lot less frustration. Just $47 for lifetime access!
joegardener Online Gardening Academy Perfect Soil Recipe Master Class: Learn how to create the perfect soil environment for thriving plants.
Earthbound Expeditions: Great Gardens of Italy & France with Joe Lamp’l
NemaSeek from Arbico Organics
NemAttack from Arbico Organics
Proven Winners ColorChoice – Our podcast episode sponsor and Brand Partner of joegardener.com
Soil3 – Our podcast episode sponsor and Brand Partner of joegardener.com
Greenhouse Megastore – Our podcast episode sponsor and Brand Partner of joegardener.com – Enter code JOEGARDENER for 15% off your order
Disclosure: Some product links in this guide are affiliate links, which means we get a commission if you purchase. However, none of the prices of these resources have been increased to compensate us, and compensation is not an influencing factor on their inclusion here. The selection of all items featured in this post and podcast were based solely on merit and in no way influenced by any affiliate or financial incentive, or contractual relationship. At the time of this writing, Joe Lamp’l has professional relationships with the following companies who may have products included in this post and podcast: Rain Bird, Corona Tools, AeroGarden, Milorganite, Soil3, Greenhouse Megastore, PittMoss, Territorial Seed Company, Earth’s Ally, National Wildlife Federation and TerraThrive. These companies are either Brand Partners of joegardener.com and/or advertise on our website. However, we receive no additional compensation from the sales or promotion of their product through this guide. The inclusion of any products mentioned within this post is entirely independent and exclusive of any relationship.