Effect of green manure on nematode populations in onion production

Allium cepa L. (Asparagales: Amaryllidaceae) is an essential crop for human nutrition. Besides its nutritional properties, it holds an important place due to its immune-boosting effects. The effect of green manure treatments with three biofumigant plant species for controlling plant-parasitic nematodes, which cause economic losses in onion production, has been investigated. Forage turnip, Brassica rapa L. (Brassicales: Brassicaceae), brown mustard, Brassica juncea (L.) Hook.f. & Thomson (Brassicales: Brassicaceae) and common vetch, Vicia sativa L. (Fabales: Fabaceae) were grown before onion production and incorporated into the soil in May-June in the study undertaken in a grower field in Karaman Province in 2021-2024. Total plant-parasitic nematode numbers were between 0-270.9 nematodes/100 g dry soil in green manure treatments. Ditylenchus dipsaci (Kühn, 1857) Filipjev, 1936 (Rhabditida: Anguinidae) (35%), Pratylenchus spp. Filipjev, 1936 (Rhabditida: Pratylenchidae) (29%), Heterodera spp. Schmidt, 1871 (Rhabditida: Heteroderidae) (3%), Paratylenchus spp. Micoletzky, 1922 (Rhabditida: Tylenchulidae) (22%), Geocenamus spp. Thorne & Malek, 1968 (Rhabditida: Dolicodoridae) (8%) and Helicotylenchus spp. Steiner, 1945 (Rhabditida: Hoplolaimidae) (3%) were the plant parasitic nematodes. The most abundant plant parasitic nematodes were Ditylenchus dipsaci and Pratylenchus spp. Nematode populations did not differ by green manure treatments while they were affected by precipitation and varied among growing years.