Host plant status and damage threshold of Pea (Pisum sativum) and Celeriac (Apium graveolens var. rapaceum) for the temperate root-knot nematode Meloidogyne chitwoodi

Outdoor vegetable cultivation is an important economic activity, both for fresh consumption and for the frozen vegetable industry within Flanders, Belgium. In recent years, due to the intensive nature of vegetable cultivation in the open air, nematode problems increased. The quarantine root-knot nematode Meloidogyne chitwoodi causes economic damage to the most important arable crops and vegetables grown in Flanders. However, for some vegetable crops knowledge on host plant status and damage potential is scarce or lacking. The host sensitivity for M. chitwoodi and damage thresholds of the most commonly field-grown cultivars of pea and celeriac were determined, both in glasshouse and field conditions. The damage threshold values (T) for the relative fresh pod weight of pea were 10, 1, 0.2 and 0 J2 (100 cm3 soil)-1 for pea 'Cher', 'Electra', 'Geneva' and 'Pixia' respectively with up to 70% yield loss. For celeriac 'Prinz', the damage threshold was 11.0 J2 (100 cm3 soil)-1 with maximum 22% yield loss. Based on our pot trials, all pea cultivars were considered to be a good host with their high maximum population density (M) and maximum multiplication rate (a) values in the pot trials and reproductive factor (Rf) from the field trials. Celeriac proved to be an excellent host in the pot test but on the field the M. chitwoodi population declined. However, on plots with lowest yield a substantial number of M. chitwoodi was found in the roots. This is the first report of celeriac as host for M. chitwoodi.