Nematode Interactions Unit

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The Diversity of Soil Nematodes

Yield benefits from applying nematicides to potatoes (right); uninfected plants on left

Why study nematodes?

Nematodes are the most abundant multi-cellular organisms on earth and have colonised most habitats. They are microscopic and those in soil move between pores in water films on the surface of soil particles. Nematodes are used as reliable indicators of soil contamination and perturbation, because of their large numbers and easily recognised feeding habits, which enable their positions in food webs to be readily assessed. In general, the proportion of bacterial feeding nematodes in the community is larger in disturbed habitats than in those that are more stable.

Most nematological research at Rothamsted concerns plant parasitic nematodes that include some of the most intractable pests to manage in crop protection. Some pest species multiply to densities of several 100 eggs per gram soil on a susceptible crop.

Developing male and female root knot nematodes within a gall

Despite their abundance, these nematodes are often overlooked because of their microscopic size, their concealment in soil and the lack of characteristic symptoms in parasitized plants; such plants are stunted, chlorotic and often wilt because their root growth is reduced due to nematode invasion and/or feeding. Research is concentrated on cyst nematodes, especially those attacking potatoes and cereals within the UK, and root-knot nematodes that are problems on a wide range of crops worldwide. These two groups account for more than US$ 75 billion yield losses despite the use of control measures.

In developed agricultural systems nematode management has relied on the use of crop rotation, resistant cultivars and nematicides that include some of the most toxic compounds used in pest control. These products are often applied in relatively large quantities (10 Kg.ha-1active ingredient) and many are based on compounds that are 30-40 years old. There is a need to develop alternative methods of nematode pest management, which are the focus of research within the Nematode Interactions Unit at Rothamsted.