Using cover crops for nematode control
“The wide-ranging benefits of cover crops are well documented, examples include their ability to improve soil health, increase organic matter and reduce surface erosion. Promisingly, we have the potential to exploit these benefits further, by utilising cover crops for pest control, specifically nematode suppression. What makes this truly exciting is it optimises something that farmers are already doing, to address multiple issues at once in an efficient manner.
To use them in this context, it’s important to understand how they actually suppress nematodes. Given the wide range of species and cultivars available for use as cover crops, it’s no wonder that some have beneficial effects against nematode species through very different methods.
Firstly, certain cover crops are simply a poor host for nematodes, starving them of food and thus making it an unappealing environment for their survival. A good example of this is black oats, used for root lesion nematode control.
In contrast to this, others are highly attractive to nematodes, but stop them from completing their lifecycle by preventing the development of adult females. These are known as trap crops, such as oilseed radish for beet cyst nematode reduction, or solanaceous species for potato cyst nematode (PCN) suppression. In some cases, these are extremely efficacious, achieving up to 90% control of the pest.
Legumes and brassicas
Other cover crops, naturally suppress nematodes by secreting compounds from their roots into the soil. For instance, leguminous plants such as lucerne release a type of secondary metabolite known as saponins, which can damage the membranes of nematodes.
Finally, we have a technique called biofumigation. This describes the process of growing brassica cover crops such as oilseed radish and Indian mustard that are naturally high in glucosinolate compounds. These plants are then crushed and incorporated into the soil, where a reaction takes place that releases toxic compounds, highly effective at PCN control.
Not without caution
As well as much positivity around the use of cover crops, it’s important to provide a balanced argument and address potential concerns. Some types of cover crops indeed have the potential to be a host for other unwanted pests and diseases. Being aware of field history and having access to available site data will help to mitigate this risk and provide insight when selecting the type of cover crop. Best4soil is a useful website for understanding cover crops and crop rotation in relation to nematodes and soil borne pathogens.
Studies have also taken place that look at the effect of biofumigation on non-target, beneficials. The work has shown that although they do have an effect, it is brief, and recovery is quick.
The ultimate outcome for all this work would be to identify viable cover crops with multi-faceted benefits, including a potential end market, whether that be as a food crop or animal feed. This could mean growers could look after their soil health, manage pests, and use it as a profitable product, all in one. That would truly maximise efficiency and be a huge win for applied research.”
Look out for part two of this series, where Dr Back explores methods to make cover crops even more effective at nematode suppression.
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Please note, the opinions expressed in this article are the author’s own and do not necessarily reflect the views or opinions of CHAP.