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'Tackling onion fly with useful nematodes'
After successes in greenhouses and mushroom cells, BASF is currently testing the possibilities for biological insect control with beneficial nematodes in outdoor cultivation. The approach to onion fly is expected to be ready for practical use in 2023. And more applications beckon.
"We are indeed going outside," laughs Piet van Boven of BASF. In the Netherlands, the technical product advisor for bioinsecticides is responsible for the testing and introduction of methods for biological insect control. He is part of an international team that has more than ten years of experience with these applications. "Biological insect control is already very common in greenhouses and mushroom cells," says Van Boven. "Because you usually grow the same crops there year after year, you will have to deal with resistance to insecticides relatively quickly. So the biological approach has already started there." In the outdoor cultivation of peonies, the use of the nematodes has been practiced for a few seasons and in 2021 BASF started the first practical tests in the Noordoostpolder with nematodes against onion flies.
Digest onion fly larva
De NemasysBASF nematodes penetrate the prey organism (here the onion fly larva), after which a bacterium that carries the nematode ensures that the larva is digested. This serves as food for the nematode. Because the larvae are exhausted at some point, the nematode cannot really reproduce. That is why a new nematode application is necessary for the next flight of the onion fly. "In principle, this application can be done with a field sprayer," says Van Boven. "But because the nematode needs moist soil to move, you have to irrigate afterwards. We used a machine for the administration of the nematodes that is normally used for spreading paper cellulose. This machine can release a lot of water. the nematode effect benefits. We use 1 to 2 liters of water per m² during the nematode application. Even after application, the soil must remain moist."
Less downtime
15% to 20% more plants were counted on the treated practice plots. "So the nematodes resulted in less loss," says the product advisor. "That is in line with the results of Uireka onion flight tests." This spring, the BASF experiment will be repeated at several locations in the Noordoostpolder. "We are now going to do more intensive crop observations than last year. We count at more times and also more accurately. We work with insect cups for the onion flies and special abacuses for the plant numbers. And we will also measure the yield." Under ideal circumstances, two treatments are sufficient, Van Boven now knows. "But the method is still more expensive than chemistry. That is why we now mainly focus on edges along roadsides, forest edges and other onion plots. Those are the entry ports."
More possibilities
Van Boven expects that the method for the onion fly will be ready for use in 2023. "But whoever wants to can NemasysBuy nematodes already," he reports enthusiastically. The introduction of the useful nematodes against insects in outdoor crops will not stop with onions, Van Boven expects. "We are already working on thrips in leeks in the Netherlands. In Germany and England we are looking at the cabbage fly. Nurseries already use the nematodes against yew beetles and grubs. And don't forget the recently introduced snail nematodes Nemaslug 2.0. This new product is an additional weapon to combat slugs in a natural way."
