France: Bait plants, one of the interesting means of control for wireworm in potatoes

After the Taupic research program, which looked at alternative levers for combating wireworms, hello Taupifast, work led by Inov3PT which starts this year and will continue until 2030. In this project, which aims to review potato crop protection strategies, "most of the plots are located in Brittany. The aim here is to remove a certain number of obstacles, in particular that concerning the biological knowledge of this larva. There is a big knowledge gap ," summarizes Éric Kerloc’h, technical manager at Bretagne Plants Innovation. France lists 6 species of this beetle, 3 are present in Brittany (Agriotes lineatus, Agriotes obscurus, Agriotes sputator).

• Overall, the baits are 30 to 40% effective.

Tillage, use of service plants, and the pest’s appeal or otherwise will be examined. The future of pest control will involve "a combination of strategies, such as good liming, good physical (aerated soil) and chemical fertility, and long rotations that reduce wireworm pressure."

Bait to divert

Among the areas of research is that of bait plants. Similar to what has been tested in corn cultivation, Bretagne Plants Innovation’s experimental technician, Mickaël Guillo, is observing the effect of sowing wheat or peas while topdressing potatoes, the aim being to divert wireworms to these cover crops rather than to the crops.

This test was made possible by manufacturing a prototype: starting with a haulm shredder, a starter fertilizer hopper was mounted on the machine. The seeds were sown using a disc, then a press wheel was used to complete the planting. The bait plants were sown in the sieved part of the soil, a loose, stone-free part, in August. "There may be earlier attacks, but it is at the end of summer that the larvae are most present in the tubers . "

Effective technique

• Regarding density, wheat was sown at 50 kg/ha, peas at 30 kg/ha.

Overall, over two years of experimentation (2023 and 2024), "the technique is effective. We observe on average a reduction of 30 to 40% in the number of galleries. Good emergence of the bait is a condition for success. We should not hesitate to sow deep if conditions are dry ." A side effect of the trial is that sowing another species "has an effect on erosion in the inter-mounds in the event of heavy rain ." These conclusive tests will continue in 2025, with barley, which is said to have a stronger attractive power than wheat.

Fanch Paranthoën