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Pest Management

Bayer Crop Science

Nematode control: six steps that will protect potatoes from PCN and FLN

Article overview

Soil dwelling nematodes are a serious threat to crop performance. They affect a range of crops including potatoescarrotscerealsraspberries and strawberries, both directly and indirectly often inflicting severe economic losses.

Soil dwelling nematodes are separated into migratory (free-living) and sedentary types. Sedentary types such as cyst nematodes (Globodera species) are characterised by being permanently attached to the roots of their host plants once they start to feed and reproduce.  Conversely, free-living types, such as needle nematodes (Longidorids), stubby-root nematodes (Trichodorids) and root-lesion nematodes (Pratylenchids), move freely through the soil between feeding bouts. While the two types often co-exist, the presence of one is not dependent on the other.

The damage they inflict is directly dependent on the size of the population present and their impact can be exacerbated by other organisms, such as bacteria and fungi, invading the root via the lesions caused by nematodes. For instance, there is a well-documented relationship between the density of PCN present in potato roots and the incidence of stolons infected with Rhizoctonia solani and the level of stolon pruning and stem canker.

In the case of potatoes, PCN-affected plants show early-stage damage through reduced vigour and stunted growth which leads to reduced light interception. Ultimately, this leads to lower yields through variations in dry matter and tuber size.

The extent of any impact is largely determined by the level of infestation. For G. rostochiensis, yield losses of up to about 20% and 70% have been observed for populations of 8 and 64 eggs per gram of soil respectively. Infestations of G. pallida cause similar symptoms to G. rostochiensis, but the impact is more serious with a quoted damage threshold as low as 1 to 2 eggs per gram of soil. 

The impact of free-living nematodes is harder to gauge because populations and infestation levels are more heavily influenced by soil type, environmental conditions, cropping history and the variety planted.

Tackling nematode populations is far from easy and no single action will deliver the 98% effective control needed to prevent a population increase. To succeed, a combination of measures including cultural and chemical controls is required.  Here we consider some of the measures available to growers and their contribution to control.  The steps that follow assume soils have been tested to identify species and population density with areas of infestation mapped.

Key steps:

Research indicates that once PCN has been detected it can remain viable in that soil for at least 40 years, but that spontaneous hatching even in the absence of potatoes means there is a natural rate of decline. This is reckoned to be at its greatest in the first 10 years. Consequently, the AHDB suggests rotations of at least 6.5 years as a necessary first step to successfully managing populations.  Rates of decline, however, vary depending on the species present and soil type while incorporating other methods of control may improve rates of decline, so management should be devised on a field specific basis.


Table 1: Estimated number of years to reduce infestation levels to an acceptable level


P (eggs per gram of soil)





 Decline rate

(% per annum)
















Reproduced from AHDB Potatoes 1240001 FINAL Report

We highly recommend:

  • Insecticides

    Velum Prime

    Velum Prime is a nematicide for use in potato and carrot crops. It is a liquid formulation and has no statutory harvest interval.

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