Agron. Sustain. Dev. 36, http://doi.org/bs8x (2016)

Root-knot nematodes (Meloidogyne spp.) are a major agricultural pest, especially of crops grown under glass or other shelters. Nematicides are expensive and increasingly restricted on environmental grounds, while resistant crop varieties are few and only partially effective. Mireille Navarrete from the French National Institute for Agricultural Research, Avignon, and colleagues have field-tested an alternative approach, using nematode-resistant sweet peppers as a ‘trap crop’ in rotation with commercial crops.

Credit: NIGEL CATTLIN / ALAMY STOCK PHOTO

The peppers carried two resistance genes: Me1, which induces a hypersensitive response preventing the development of egg-laying females, and Me3, which causes cellular necrosis adjacent to infecting worms. Both strategies kill nematodes before they can reproduce, clearing them from infested soils, at least under experimental conditions. Over four years on a commercial farm in southern France, the researchers tested a cropping scheme in which peppers were grown every two years intercropped between Swiss chard, lettuce, tomatoes and melons. This regime reduced nematode infestation of the soil by over 80% and more than halved the occurrence of nematode-induced galls on the Swiss chard crops.

Despite the success of the trial, this approach will not suit everyone. Of 28 local farmers surveyed, 4 in 5 were worried that the peppers would interfere with their summer growing season and be too labour-intensive. Nevertheless, this trial shows that using resistant cultivars as trap crops could prove a practical defence against nematode pests.