Potato cyst nematodes (PCN) and their management in potatoes

There are two species of PCN, Globodera rostochiensis and Globodera pallida.

G. pallida has become widespread due to its prolonged hatching period and the selection pressure created by the cultivation of many varieties that are resistant to G. rostochiensis but susceptible to G. pallida.

The PCN cyst is the dead body of the female nematode, containing up to 600 viable eggs, each of which contains a dormant juvenile. Potato roots produce substances called hatching factors, which stimulate PCN eggs to hatch. G. rostochiensis hatches fastest and the hatching period usually lasts about 18 weeks in G. pallida and 12 weeks in G. rostochiensis.

The lifecycle consists of four juvenile stages and an adult. First stage juveniles develop and moult to become second stage juveniles (J2) within the egg. Juveniles (J2) invade the roots and settle in the root tissue near to vessels that conduct food and water and form a ‘syncytium’, a complex food transfer cell. This causes much of the damage to the crop by stunting root growth and reducing uptake of nutrients and water from the soil. The maturing female enlarges and, in doing so, ruptures the root and becomes exposed outside the root eventually forming the egg-containing cyst.

Multiplication of PCN is greater when the initial infestation is low. For example, populations of G. pallida can multiply between 46–100 fold from an initial population of fewer than 10 eggs per gram of soil.

An IPM approach is required to deal with PCN, including:

• Sample soil to detect the presence of PCN and, if confirmed, determine the PCN species and population levels because these will influence the choice of management options
• Extend rotations to reduce PCN levels: there are PCN tools that demonstrate the interaction between variety, rotation length and PCN population
• Control volunteer (groundkeeper) potatoes
• Use certified seed potatoes, produced on land tested for freedom from PCN
• Ensure hygienic practices that limit the movement of soil, including that from graders
• Use varieties that are resistant to the species of PCN present
• Use trap cropping and biofumigants in the rotation
• Use a nematicide

The management of PCN has been studied at Strategic Potato Farms and through the Innovative Farmers initiative. Topics covered include: assessment of variety tolerance to PCN, trap crops, and biofumigation.