Nematodes are a cosmopolitan group of organisms found in all environments from the tropics to the polar caps.
The majority of nematodes are microscopic (less than 1 mm), although some parasitic nematodes, of whales for example, can be several meters in length.
Nematodes have had a long association with human society as parasites, not only of people but also of domesticated plants and animals.
More recently their beneficial effects have been appreciated as regulators of pests and diseases, and they play a functional role as important components of ecosystem services in aiding the cycling of nutrients.
- Globally, plant-parasitic nematodes are estimated to cause around £70 billion worth of damage annually (Fig. 1).
- In the UK, potato cyst nematodes Globodera species, cause annual losses of around £50 million.
- Plant-parasitic nematodes can be controlled by the use of synthetic nematicides but these are highly toxic to humans and the environment.
- Their toxicity has led to legislation in Europe, the USA and elsewhere to prohibit their use; alternative control methods are being sought.
Research into controlling nematodes
Research by Dr Keith Davies at the University of Hertfordshire focuses on developing environmentally benign methods to control these economically important pests.
Research in the 1960s established that certain soils are suppressive to plant-parasitic nematodes and these soils have developed a microbial flora that is high in fungi and bacteria that are parasitic on nematodes.
Fig. 2 (above): The head of a root-knot nematode juvenile with endospores of the bacterial hyperparasite Pasteuria penetrans.
Investigations are on-going to understand these nematode suppressive soils and to develop novel control strategies as an alternative to nematicides.
Research focuses on:
- Integrating molecular knowledge of nematode microbe interactions so that strategies can be developed that can control the biodiverse nematode populations that occur in field soils.
- Using knowledge of innate immunity in the model nematode Caenorhabditis elegans to gain insights into microbial pathogenesis and to exploit weaknesses in the nematodes susceptibility to pathogens.
- Exploiting what appears to be natural promiscuity of some bacterial parasites like Pasteuria (Mohan et al.,2011, FEMS Microbiology Ecology 79: 675–684) to maintain a broad host range.