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