Potato Cyst Nematode

Key Points

• Potato Cyst Nematode infestation affects both yield and quality
• National yield loss due to PCN infestation is estimated as at least 10% annually
• Telone II controls all species, including Globodera pallida
• Applications can be made at any time in the rotation
• Specialist contractors provide a full soil sampling and application service
• Reduced slug damage to potatoes has been observed after use of Telone II

Introduction

Potato Cyst Nematodes (PCN) are the most widely distributed pests of potatoes in the UK, affecting both yield and quality. National yield loss due to PCN infestation is estimated as at least 10% annually. Potato cultivars are often described as being resistant or tolerant to PCN. Resistant varieties do not allow PCN replication and there is minimal effect on yield. Tolerant, or partially resistant, varieties suppress replication, keeping PCN populations at low levels.

Biology

There are two main species of Potato Cyst Nematode (PCN) affecting potato crops in the UK. They are Globodera pallida, the white or pale PCN, and Globodera rostochiensis, the yellow or golden PCN. The colour relates to the cysts produced, before they mature and turn brown. Both are major pests of potatoes in the UK.

PCN cysts are the only stage of development easily visible without magnification. They are initially attached to potato roots but later occur free in the soil. A cyst is the dead remains of a female nematode. At maturity they are spherical, about 0.5mm in diameter, and dark reddish-brown in colour, in both species, with a tough skin. A cyst can contain 200 to 600 nematodes, each coiled within an egg. If hatched nematodes can not find a potato root to invade they will die in the soil. However, unhatched cysts can remain viable in the soil for more than 10 years.

When potatoes are planted in infested soil root exudates diffuse in to the soil and stimulate nematode emergence. These nematodes then invade the roots and begin to feed. In areas of severe infestation roots can be seriously damaged and sometimes killed. If a plant attempts to overcome attack by forming new roots these are also attacked. Once within root tissue females swell until they become almost spherical. The head remains within the root but the remainder of the body splits the root tissue and becomes exposed at the surface. Females are then fertilised by male nematodes that have emerged from roots. When an infested crop is lifted many mature cysts remain in the soil as a source of infestation for future potato crops.

Fields infested with PCN can carry several million cysts per hectare and they are easily spread whenever soil is moved from field to field, e.g. on farm or contractor machinery. Large populations of nematodes normally build up where overcropping of potatoes occurs. Nematode numbers can be decreased by not planting potatoes for several years in heavily infested fields, but this action is not always practical from a rotational cropping perspective. Soil sampling should always be used to give an indication of PCN populations present in a field or part field. Unfortunately, not finding evidence of PCN in a soil sample does not guarantee problems will not arise if an unprotected potato crop is planted.

Product Choice

An integrated approach must always be used in an effort to manage Potato Cyst Nematode populations. This involves the use of suitable rotation intervals between crops of potatoes, one year in six is recommended and one year in five is a practical minimum; use of Telone* II as a soil fumigant; and granular treatments to prevent populations returning to pre-treatment levels.

Telone II soil fumigant is a liquid nematicide containing 1,3-dichloropropene. When injected in to the soil it volatilises into a gas and permeates through the soil. The gas then dissolves in the water film surrounding soil particles and controls all species of Potato Cyst Nematodes and free-living nematodes. Unlike granular treatments for the control of PCN, Telone II has long-lasting effects and benefits. Applications of Telone II, normally made in the autumn months and always by specialist contractors, will give very high levels of control of Globodera pallida and Globodera rostochiensis. Other crops in the rotation, e.g. sugar beet, will also benefit from an application of Telone II.

In many situations Telone II can be applied alone. There are circumstances where a program incorporating Telone II and granular treatments can be advantageous. PCN at low population levels have the ability to multiply greatly during the growing of a single potato crop. A key integrated management principle should be to reduce PCN populations to a low level and maintain this position. Telone II can significantly reduce a population and the inclusion of a granular treatment will increase final yield and, importantly, prevent the low population from multiplying and returning to pre-treatment levels.

Soil fumigation with Telone II can be carried out at any point in the rotation. Application following ploughing, immediately after lifting a potato crop, takes advantage of optimum soil conditions for effective nematode control, followed by a natural decline on non-host crops. Potatoes can then be planted later in the rotation when PCN numbers are well below a population level that will seriously limit yield.

Where the need to use Telone II has been identified, either by previous history or through soil sampling, the following program will ensure optimum application and efficacy.

A steady decline in cyst populations together with other beneficial effects such as controlling other nematode species, increasing yields of other crops and potentially reduced nitrogen inputs make soil fumigation with Telone II economically very attractive.

Learn more about Telone II