Spread
Nematodes do not usually spread quickly and infestations will only naturally spread at most a metre annually. They are more likely to be spread or introduced to new areas by movement of infested equipment, soil and plant material between paddocks. It is important to source clean seedlings and seed potatoes and follow good hygiene practices.
Control
Paddocks can be checked for presence of root-knot nematodes prior to seeding, however this may not be a reliable indicator as distribution within a paddock is usually patchy and infested areas may be missed. The best time to check is prior to harvest. This will help you manage the next crop.
If your crop has areas where plants are showing symptoms, dig up both healthy and poor plants for comparison. Shake off the dirt and examine the roots for swellings (usually 1–10mm in diameter but can be bigger) and blisters on potato tubers or forking in carrots. If these symptoms are present, your crop may be infected. Soil and plant samples can be sent to AGWEST Plant Laboratories for confirmation. Sampling instructions and submission forms can be found at Plant disease diagnostics.