Using nature to protect plants

Sarah James, PhD, counts how many nematodes are in 1 gram of the product.

Biopesticides offer a way of using nature against itself. We take a look inside a BASF production site that breeds nematodes – tiny worms that can be used in plant protection to control a wide variety of pests.

Site manager Mark Downing (left) and fermentation manager Tom Goddard discuss the servicing of the fermenter tanks.

It’s not often you get to look inside a huge tank filled with eight trillion tiny worms. The worms in question are beneficial nematodes, bred in one of BASF’s crop protection sites to be sold as a biological pesticide. Nematodes are ideal for plant protection. They actively seek pests like slugs, weevils or caterpillars, invade and devour them. The site has been located in Littlehampton on the English south coast for more than 30 years and is now the largest nematode production facility in the world.

Site manager Mark Downing oversees a team of 35 employees. “We’re not out to replace chemical pesticides, there is a need in the market for both,” he says. “But with increasing demand for organic production and tougher regulations, we are getting a foothold.” Downing is joined by fermentation manager Tom Goddard and formulating and packaging scientist Sarah James, PhD, to give us a tour of the factory floor.

The first room is filled with shiny cylindrical tanks and a bewildering array of pipes that snake their way around the site. The process starts by passing nematodes through an insect. “This is to prove their efficacy,” explains Goddard. Only the nematodes that kill the host insect are used. They are transferred to a flask, where they are encouraged to feed on nutrients and then used to seed smaller tanks. The process is scaled up in ever larger vessels until the nematodes have multiplied from a few thousand to trillions. The nematode lifecycle has five stages. Those that go on the market are the infective juveniles – the only stage where they can survive outside a host. Currently the facility produces six different species of nematodes to target different kinds of pests. Some are ideal for managing fungus gnats, root flies and western flower thrips in horticulture and vegetable production. Others provide control of slugs, codling moths and red palm weevils. BASF works with local and international researchers to discover new, potentially useful species.

Nematodes are ideal for plant protection. They actively seek pests like slugs, weevils or caterpillars, invade and devour them.

Petri dishes with cultures of symbiotic bacteria (see infobox): They naturally occur in the nematode’s gut, but at the lab nature is given a helping hand by introducing the bacteria into the vessel in which the nematodes will be bred.

In the middle of the production facility stands “El Gordo,” Spanish for “the fat one.” A 102,000-liter vessel, about 12 meters high, it is used to brew the Steinernema feltiae species, which is marketed under the brand name Nemasys®. “That’s our biggest selling product,” says Goddard. “We sell trillions of these nematodes a year.”

Once brewed to the right stage, the nematodes are mixed with a special formulation and packed into what look like microwave dinner trays. Goddard shows two packs containing over 1.5 billion nematodes which are destined for Florida, to help tackle pests that are threatening orange groves. “This will cover something like 15 acres, or around nine soccer pitches. It’s diluted in a tank with water, then sprayed on the crop,” he says.

James works in the formulating and packaging lab finding ways to overcome problems like overheating. The heat comes from the nematodes’ metabolism as they feed. With the tanks containing up to 200,000 nematodes per milliliter, this is a serious concern. She shows three containers of new formulations she has mixed as an experiment to find out what will improve the shelf life of a living product. James joined BASF as she was finishing her PhD. “I was studying ways of using nature against itself. I like the idea of using a natural predator to target what we consider pests,” she says. The Nemasys product typically kills 60 to 80 percent of the pests on plants.

“The market for nematodes started small but is growing every year,” says Downing. “We like to think we’re providing the technology of the future.”

Nematodes are multicellular worms, around 1 millimeter in length. They live in soil and a wide range of other land and marine environments. Each species has its own symbiotic bacteria which live in its gut. Once a nematode invades a pest, it regurgitates the bacteria, which then digest the host. The resulting material has a distinctive color – from bright yellow to rusty red. The color can identify the species. They find their food by “chemotaxis,” their movements responding to chemical stimulation. After devouring one host, they look for more, but can survive for up to 10 days without a meal. There are nearly 20,000 known species of nematodes, and estimated to be many more.  

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