Why pesticides are a source of microplastics
Current methods of applying agrochemicals, such as fertilisers, fungicides, and other pesticides, contribute to microplastic pollution. Most of them still rely on microplastic particles. Besides, commercial formulations contain additional chemicals, such as wetting agents, to spread evenly and stick to leaves. As new European regulations restrict the use of microplastic particles, crop protection products need to be redesigned.
“We must be much more selective in how crop protection is done today,” Prof Frederik Wurm, the chair of the Sustainable Polymer Chemistry (SPC) group at the University of Twente, says. “The world population is growing, and people need to be fed, but agricultural practices have hardly changed for decades.”
The SPC group has been developing biobased and fully biodegradable particles, which carry agrochemicals to specific locations. These so-called nanocarriers are microplastic-free and made from biodegradable polymers such as lignin, cellulose, or polyesters. At the end of their life cycle, they are designed to break down naturally in soil, without leaving toxic residues behind.
Stickier than commercial products
One of the main problems in pesticide application is what happens when it rains. Does the product stick to the leaf, protecting the crop from plant pathogens such as fungi, or does it wash off and end up in the soil? The particles Wurm’s group has developed are stickier and therefore more effective than commercial products.
“By controlling the size of the particles, we were able to make the particles stick much better to leaves than commercial products. The smallest particles are only a few hundred nanometres in diameter: this is 10 to 100 times smaller than those in many existing commercial formulations,” he says. At this scale, the particles can settle into the ridges of the leaf surface, which makes them harder to wash away by rain.
Fighting mildew with nanopasta
The research group is also studying how the shape of the particles affects efficiency against plant pathogens. Wurm: “The biodegradable polymers we use can self-assemble into different shapes. For example, some are a bit rod-like, they look like tiny spaghetti. And when they are applied to a leaf, they form a kind of network, which makes it very adhesive.”
The team is currently testing the particles against mildew, a common fungal disease, which is difficult to control and affects strawberries, tomatoes, and grapevines, among other crops. “Our experiments on mildew-infected strawberries so far show that the biodegradable particles are at least as effective as commercial formulations. We are preparing the results for scientific publication.”
Towards crop-specific, sustainable plant protection
Wurm: “Our vision is to rethink plant protection and develop formulations tailored to specific plant species because leaf morphologies differ, and that affects how particles attach and spread.” In the long run, their approach could be customised to individual crops, for example, one formulation for strawberries, and another for grapevines.
The SPC group’s work builds on its research in polymers, plastics, and packaging. They are now applying that expertise to reducing microplastic pollution in agriculture.
And what about the wine? “It is drinkable,” Wurm laughs. Cheers, UT.
