Plant-parasitic nematodes associated with horseradish in Illinois

Eight genera of plant-parasitic nematodes (with seven identified to species) were identified from Illinois horseradish production fields in 1999, 2000, 2001, and 2003 and included Helicotylenchus pseudorobustus, Hoplolaimus galeatus, Meloidogyne spp., Paratylenchus projectus, Pratylenchus sefaensis, Quinisulcius acutus, Tylenchorhynchus annulatus, and Xiphinema americanum. Pratylenchus sefaensis is reported in Illinois for the first time. Helicotylenchus pseudorobustus, P. sefaensis, T. annulatus, and X. americanum are the most prevalent plant-parasitic nematodes associated with horseradish in southern Illinois at the present time, as these nematodes respectively occurred in 70%, 63%, 56%, and 39% of samples collected from horseradish fields during the four growing seasons. Other nematode genera identified usually occurred at low population densities. There are no established damage threshold levels for plant-parasitic nematodes in horseradish, but it appears that population densities are currently not high enough to be considered a threat to horseradish production in Illinois.