Pest control can happen naturally, says EU


Source: European Commission, Environment DG

Pesticides commonly used to control root-feeding nematodes are harmful to the environment and reduce soil biodiversity. By studying natural plant populations, researchers have observed that soil microorganisms and other naturally occurring predators, can effectively control nematode species. These natural forms of control could be adapted as biocides and potentially play a major role in sustainable agriculture.

Plant pathogenic nematodes are small, worm-like creatures that can attack almost all major crop species. They cause large yield losses in European potato and sugar-beet crops1. Nematode control relies heavily on the use of highly toxic pesticides, called nematicides, of which European farmers apply up to 10,000 tonnes each year1. This practice is harmful for the environment and can reduce biodiversity by destroying beneficial organisms that live in the soil.

Currently it would be difficult to produce crops sustainably without the use of nematicides. However, biological control mechanisms that employ naturally occurring fungi, bacteria, and other microorganisms to fight crop pests such as nematodes, could be an alternative.

Research shows that the effects of root-feeding nematodes on wild plant populations can be significantly lower than effects on cultivated crops. The study, conducted under the EU-funded EcoTrain project2, investigated the use of microorganisms and other soil-dwelling species that live in the root zone soil of a coastal dune grass (Ammophila arenaria) as a control of nematode pests. They tested a range of treatments on eight different species of nematode. The treatments were: microorganisms, a mixture of other nematodes and microarthropods (small insects such as mites).

They found that each nematode species responded differently to the treatments. For example, microorganisms were able to suppress one nematode species by 87 per cent. However, suppression of other species was lower. Adding a mixture of other nematodes effectively suppressed two of the test nematode species, whereas microarthropods only suppressed one nematode species.

The researchers concluded that nematode control was species-specific and varied between ectoparasitic nematodes, which feed on plant tissues from outside the plant, and endoparasitic nematodes, which feed inside the plant tissues. This suggests that biological control measures based on the use of one beneficial species would not be an effective way to control nematodes and prevent crop losses.

In the wild, the absence of pesticides allows beneficial species to thrive. A more appropriate approach to nematode control could be to treat crop soils with a mixture of organisms that mimic the diverse soil environment of wild plant populations.

Continued investigation of nematode control in nature could reveal the diverse mixtures of species needed to enhance effectiveness of nematode control in agriculture. In the meantime, conserving soil biodiversity is crucial in order to protect crops against soil-borne pests and diseases. On 13 January 2009, European Parliament approved a new Plant Protection Products regulation, which will see the phasing out of many harmful chemical pesticides in Europe and promotion of safer alternatives. This will heighten the need to find new non-chemical methods of pest control.

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