Occurrence of vermiform plant-parasitic nematodes in North Dakota corn fields and impact of environmental and soil factors

Plant-parasitic nematodes (PPN) can negatively affect corn production. In this study, incidence and abundance of PPN were assessed in 300 corn fields across 20 counties in North Dakota during 2015 and 2016. Seventy-two percent of the fields were positive for PPN. The major genera identified were Helicotylenchus (incidence: 52%; mean density: 1513 nematodes kg(-1) of soil; greatest density: 16 910 nematodes kg(-1) of soil), Tylenchorhynchus (37%; 687; 9500), Paratylenchus (31%; 1484; 7800), Pratylenchus (20%; 399; 2125), Heterodera (9%; 555; 4500), Xiphinema (8%; 330; 900), Hoplolaimus (3%; 294; 500) and Paratrichodorus (1%; 124; 200). Neighbouring counties had greater similarity in PPN diversity than counties that are further apart, with western, north-eastern and south-eastern counties forming clusters of similar nematode occurrence and diversity. Canonical correspondence analysis was conducted to determine the association between incidence and abundance of these PPN populations and various soil edaphic and climatic factors. The analysis revealed that Hoplolaimus, Paratrichodorus, Paratylenchus and Pratylenchus were positively correlated with soil temperature, rainfall and per cent sand, while Helicotylenchus, Tylenchorhynchus and Xiphinema were positively correlated with pH, percent clay and percent organic matter. This is the first report of an extensive investigation of PPN communities in North Dakota corn fields. Research findings will be useful in future field experiments to determine the impact of PPN on corn in the Northern Great Plains.