Nematodes: pest or bio-pesticide?

Nematodes are the most abundant multicellular organisms on earth, so it hardly comes by surprise that some of those organisms are harmful and others beneficial for crops. During the 33th symposium of the European Society of Nematologists (ESN), more than 400 nematologists were gathered at the University of Ghent to discuss different nematode-related topics, including their function in crop-protection, which will also be addressed during the IUPAC 2019 congress on crop protection.  

Nematodes are easily overlooked, because most are very small. However, they have various important functions in the agricultural environment. Most of them are harmless or even beneficial, but others are harmful and can be the cause of severe harvest losses.

According to Tina Kyndt, professor at Ghent University and member of the ESN 2018 organizing committee, nematodes and protection against nematodes is studied more and more and some nematodes are even used themselves in crop protection. “This might explain why this was a record edition of the symposium”, explains prof. Kyndt. “Ghent University and ILVO (Flanders Research Institute for Agriculture, Fisheries and Food) are also both well known for their expertise in nematology, which made this congress even more interesting to attend.”.

Nematodes as pest in agriculture

A number of nematodes such as potato cysts, beet cysts, root-lesion and root-knot nematodes are well known to be the cause of harvest losses. The past few years, trouble with plant-parasitic nematodes has increased in some parts of the world, like Europe, due to prohibition of soil disinfestation products and a more intensive crop rotation.

Researchers of Ghent University and ILVO are trying to identify the problems and are working towards a number of possible solutions. One common mistake is the use of the wrong cover crop. Some plant-parasitic nematode species are very selective towards host plants while others have a wide host range. To reduce the number of undesired nematodes, it is important that potential host plants do not follow each other in the crop rotation system. At ILVO, Wim Wesemael, member of the IUPAC2019 CCPC scientific committee and member of the ESN 2018 organizing committee, is conducting research on the influence of crop rotation on harmful nematode populations in the soil. “The increased use of cover crops and warmer temperatures in autumn and winter allow some plant-parasitic nematodes to complete an extra generation per year. Farmers need knowledgeable advice in their selection and use of cover crops to avoid further population build ups”, says Wesemael. 

Application of nematodes as bio-pesticide

Not all nematodes are off course herbivorous. Some of them are found to be entomopathogenic, which means they will feed on insects. In this way, nematodes can help in crop protection by the elimination of certain pests. “The choice of the species of entomopathogenic nematodes should be made with care, because one nematode species will only feed on a small amount of insect species, but this also has the advantage that no non-targeted organisms will be killed”, says Kyndt.

A vision on nematode control

Since more and more conventional products against nematodes are prohibited due to environmental and health issues, only a few chemical products remain to protect crops against nematodes. Therefore, there is a direct need for alternatives.

At Ghent University, prof. Tina Kyndt is researching the potential of plant- and waste stream extracts to induce resistance in plants against nematodes. “The concept is to treat plant leaves with compounds that can turn on the plant defense response. When the plant is attacked by nematodes, the defense system is already active, comparable to a vaccination”, explains prof. Kyndt.  

“This vaccination is a promising technique and has the potential to become more generally used and increase the farmer’s toolbox. Especially, as the pressure on chemical crop protection is increasing due to public opinion.”, concludes prof. Kyndt. That is why this topic will also be addressed during the IUPAC 2019 congress on crop protection chemistry.