A gentleman walked into the Extension office with a sample of a compacta holly that was struggling to survive. I immediately suspected it could be root-knot nematodes because compacta hollies are extremely susceptible to this roundworm. He collected a sample, sent it to the NCDA and sure enough, his soil tested positive for nematodes.
Soils usually contain many free-living, or non-plant-parasitic, as well as plant-parasitic nematodes. Often, several genera of plant parasites are present in the same soil, though only one or two may cause major plant damage.