Harmful chemical pesticides are by no means a thing of the past. And yet the transition from chemical to biological crop protection is going better than many critics believe, say board president Louise Fresco and researcher Jürgen Köhl.
Illustration Geert-Jan Bruins
The Royal Netherlands Society of Plant Pathology (KNPV) celebrated its 125th anniversary last week with a conference on the history and the future of crop protection. Good timing, as there has been a lot of criticism recently of chemical pesticides such as glyphosate and neonicotinoids. Wageningen UR president Louise Fresco’s talk at the conference was a bit of a pep talk. She declared science to be the key to a sustainable, resilient global food production system. Critics would have us believe that large-scale intensive agriculture with its chemical crop protection is problematic, she said, but in fact it has been a great success. Great strides have been made using traditional plant breeding to combat agricultural pests and diseases. Not so very long ago, one in five people worldwide suffered from hunger; that figure has gone down to 11 percent of the world population. There are now more obese than undernourished people, said Fresco, citing a recent article in The Lancet.
In fact, that article revealed that half of today’s world population has an unhealthy diet one way or another: eating too little, too much, or an unbalanced diet. Fresco: ‘The challenge today is to produce healthy, safe food for the future world population. To do that we need agriculture, and that agriculture is a complex ecosystem in which there is a continuous rat race between species we want and species we don’t want.’ In this context, new breeding techniques and integrated crop protection are going to ensure that we are less dependent on chemical pesticides, predicts Fresco. She talks of ecotechnology, based on a thorough knowledge of the natural enemies of pests, or of the soil life around plant roots, combined with modern breeding methods and precision agriculture.
Wageningen phytopathologist Jürgen Köhl is already working here on the EU project Biocomes. He and other European researchers as well as companies want to develop biological pesticides for major diseases and pests such as aphids, diamondback moths, whiteflies, bacterial wilt, Fusarium fungi and mildew. Sometimes these pests and plant diseases can be successfully dealt with in greenhouses, but not yet in the open air. This is because a pest’s natural enemies react more strongly than chemicals do to environmental conditions such as temperature, humidity and UV light.
Köhl and his project team are looking for an effective biological pesticide against mildew, a fungus that affects grains, apples and strawberries among other products. To this end he collected mildew colonies and isolated micro-organisms in them which have mildew on their menu. Köhl identified as many as 1200 ‘isolates’, as he calls them. Project staff evaluated their suitability: do they survive outdoors and above ground? Can they withstand UV light, low temperatures and drought? Nearly 200 of the 1200 candidates got through this screening.
From this group Köhl selected the most promising micro-organisms, which are now being bred on campus. They will be taken outdoors in May, when Köhl will find out whether they can survive out of doors and whether they can tackle mildew effectively. Meanwhile the participating company is looking into whether the candidates are suited to mass production and whether they stay in one piece between production and application in the field. If a natural enemy passes all these tests, we will have a promising biological pesticide for mildew.
But then comes the next test: the one for market access. A consultancy bureau with a knowledge of the registration process and legislation on biological crop protection is advising Köhl on which candidates are likely to get through the application procedures relatively easily. Using parasitic wasps to tackle aphids, for instance, requires a relatively straightforward risk analysis, but admission procedures for a fungus require a risk analysis on a par with that for chemicals.
The Bicomes project runs until the end of 2017, by which time Köhl hopes to have a biological treatment for mildew. European colleagues of his are working meanwhile on a ‘supernematode’ that can control the destructive maize stalk borer. In this case, the researchers are going to ‘upgrade’ the useful nematode through genetic breeding.
Besides this search for strong natural enemies of a pest, Köhl is interested in another form of biological crop protection in which the natural diversity in an ecosystem is used as a buffer against diseases and pests. ‘Through the new molecular techniques we are getting a clearer and clearer picture of the microbiome of the leaf or around the roots. If we can find out all the functions of the bacteria, fungi, viruses and nematodes in a community of this kind, it will open up all kinds of new possibilities. I expect that with this approach we can strengthen ecosystems’ resilience to pests.’ The knowledge will not result in a product, as in the case of biological crop protection, but in guidelines or a planting scheme, expects Köhl.
Breeding for resistance
Biological crop protection currently accounts for only 3.5 percent of the total; there are still no biological alternatives to the most widely used pesticides. But the bio-control companies are growing by an average of 16 percent per year, and are professionalizing fast, says the researcher. Many chemical companies have started investing in biological crop protection as well, by taking over producers of biological products for example.
Progress has also been made in breeding for resistance, says Fresco. ‘Great strides have already been taken using classic breeding techniques, such as building resistance to stripe rust into wheat varieties. But now that an aggressive strain of this fungus has turned up, resistance can easily be built in using the new Crispr-Cas technique, which alters the plant’s genome with great precision. I think this technique also paves the way for resistance breeding of crops which are of less economic value, such as cassava and bean species in Africa. This increases harvest security and reduces dependence on pesticides. Once again, science is the key to success, but then we do have to have a support base in society.’
Exhibition on plant diseases
The Forum library has created an exhibition about plant diseases to mark the 125th anniversary of the Royal Netherlands Society of Plant Pathology (KNPV). On display are unusual books by Hugo de Vries and Jan Ritzema Bos and unique drawings by artists such as Harmen Meurs, Ben van Londen and Suzon Beynon. The exhibition runs from 11 April to 7 October 2016 and is open Monday to Friday from 9.00 till 13.00 hours.