A multi-county survey of plant-parasitic nematodes in North Carolina tobacco fields
The genera of plant-parasitic nematodes (PPN) known to infect tobacco include root-knot nematodes (Meloidogyne spp.), lesion nematodes (Pratylenchus spp.), the tobacco cyst nematode complex (Globodera tabacum), and stunt nematodes (Tylenchorhynchus spp.). Their prevalence in commercial fields planted to flue-cured tobacco have not been quantified in North Carolina. In August 2021 and September 2022 a total of 188 soil samples were collected from tobacco fields in 24 counties in order to identify nematode genera and quantify density. Where Meloidogyne spp. was identified, PCR was performed to determine the presence of M. enterolobii, or Guava root-knot nematode, which is a newly identified invasive species. Stunt nematodes were identified in 2021 and 2022 in 67.8 and 80 % of the soil samples, respectively. Slightly less prevalent were root-knot nematodes at 31.4 and 50 % in 2021 and 2022, respectively. Meloidogyne enterolobii were only identified in 2022 in Pitt and Granville Counties. This was the first report of M. enterolobii in Granville County. Lesion nematodes were generally as common as root-knot, accounting for 33.1 and 50 % in 2021 and 2022, respectively. Tobacco cyst nematodes were only identified in 2021 in Stokes County, which is in the Old Belt production region of the state. Tobacco cyst nematode was present in 100 % of the Stokes County samples (n=8) but only accounted for 6.8 % of all nematode genera identified in 2021. Our results suggest that PPN remain a serious pest for tobacco producers and that the spread of the invasive Guava root-knot nematode should continue to be monitored and managed. In contrast, the presence of tobacco cyst nematode appears to remain isolated to the Old Belt production region; therefore, sanitation measures and management strategies have proved to be effective tools to reduce its spread.