Biological Control of Plant Parasitic Nematodes

Plant parasitic nematodes are a leading biotic cause of yield loss in crops, costing world agriculture an estimated US $125 billion annually. These small (0.25-3mm), unsegmented worms can affect crops in a variety of ways: altering normal root cell division, modifying plant cells for nutrient transfer, transmitting viruses and creating wounds that permit the entrance of other plant pathogens. Yet despite their enormous impact on important crop plants through-out the world, there are no effective, environmentally safe management strategies to treat or prevent plants from nematode infection. However, recent results from the EU-funded EcoTrain Project indicate that natural forms of control could provide a long-term solution to the problem.

Current nematode management strategies are largely dependent upon highly toxic pesticides (nematicides), which are harmful to the physical environment and reduce soil biodiversity by eliminating a variety non-target species.

By investigating the regulation of plant parasitic nematodes in the wild, scientists found that naturally occurring soil-dwelling predators could effectively control various nematode species.

The scientists took various micro-organisms, non-parasitic nematodes and microarthropods (such as mites) from the soil in a coastal dune grass (Ammophila arenaria) system, and examined the effect of different combinations on eight different species of parasitic nematode. Their results indicated that the most effective and sustainable method of biological control could be to treat crops with nematode suppressing soils, which contain a variety of soil-dwelling organisms found in wild plant populations. Their results also suggest that ‘conserving soil biodiversity is crucial in order to enhance the reliability of biological crop protection against soil-borne pests and diseases’.

These findings will undoubtedly be followed up with further investigations and more extensive field experiments. Especially in light of the European Parliaments approval of the Plant Protection Products regulation, which aims to phase out many chemical pesticides in Europe and promote of safer alternatives.

However, as parasitologist Tom Powers pointed out in 1992, the difficulty with this method of control appears to be the ability to transform it ‘into management system that can be manipulated by the growers’. After over 50 years of research, there are still no biological controls that are routinely used against plant parasitic nematodes.

Original Article: Piskiewicz, A.M., Duyts, H., van der Putten, W.H. (2008). Multiple species-specific controls of root-feeding nematodes in natural soils. Soil Biology and Biochemistry. 40: 2729-2735.

The EcoTrain Project is funded by the EU's Research Training Network (RTN) Program.

Additional information:
Tom Powers (1992) Biological control of plant parasitic nematodes: Progress, problems and prospects: by G.R. Stirling, CAB International, 1991. Parasitology Today. 8: 320

European Parliament Plant Protection Products Regulations

UK Government Ready to Reignite GM Debate

The UK Government is ready to explore once more the use of GM technology in crops, hoping that this will offer a solution to the current world food crisis. Phil Woolas, the UK's Environment Minister, has reportedly held private talks with the Agricultural Biotechnology Council, an umbrella group to promote the role of biotechnology in agriculture.

In an interview with the Independent newspaper yesterday, Mr Woolas said: "There is a growing question of whether GM crops can help the developing world out of the current food price crisis. It is a question that we as a nation need to ask ourselves." Prime Minister Gordon Brown yesterday called on leaders at an EU summit to consider relaxing rules on the import of GM animal feed, as a way of lowering food costs for the poorest countries.

The only GM food crops currently available commercially are those which have been grown to be herbicide or insect resistant. There are very legitimate concerns that extensive growth of such crops will severely impact on the biodiversity of the countryside; as broad-spectrum herbicides such as Monsanto's 'Roundup' indiscriminately affect wildlife. However, GM technology could offer benefits to developing countries if the focus was on research into higher yields, drought and disease resistance. Downing Street has commented that "GM crops are to be considered on a case-by-case basis, based solely on the science".

Does GM offer a solution to hunger and poverty in the developing world as food prices rise and food shortages threaten?
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Improving Current Agricultural Practices

A new study in the Journal of Environmental Health Management identifies new farming practices that could eliminate non-target effects of pesticides by 2010.

Fungal pests are a particular problem in the Netherlands due to climatic conditions. Pesticide usage in the Netherlands has declined since 1991, however current practices still result in spray-drift, that is the spreading of pesticides onto non-target plants, fungi and insects.

Using modeling techniques, the researchers were able to measure the impact spray drift had on non-target species in three different scenarios; the recent past (1999), the present (2005) and the near future (2010). The study showed that by introducing non-crop borders around agricultural fields, pesticide impacts on non-target species could be cut to zero. The paper has strong policy implications, given that current best practice techniques result in negative impacts on 41 per cent of areas next to treated fields, despite the use of low-drift nozzles and unsprayed borders.

A European policy framework directive for sustainable pesticide use is currently being developed as is a new Thematic Strategy on the Sustainable Use of Pesticides.

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