"Strawberry cultivation has to become more sustainable"

The Dutch strawberry sector must change direction, because the cultivation of strawberries still relies far too much on conventional means. By increasing the plant resistance, the dependence on those resources may decrease. "The supermarket chains are increasingly demanding higher standards regarding the number of used active ingredients and the residue. The consumer is entitled to a completely reliable and safe product. That is what we have to work on. The possibilities and opportunities are there," according to Dutch strawberry grower Michiel Penninx.

Together with his colleague Rob van Enckevort, he took the initiative to see if strawberry cultivation could become more sustainable. To this end, the two set up a working group in which they themselves and five suppliers work together.

A necessity, because sustainability is not yet a priority among the growers, Penninx explains. "Of course, a number of growers use predator bugs and biostimulants, but there is no real progress. Often this is because of a lack of knowledge. In recent years the guidance of growers who want to become more sustainable has not been very strong."

The problem is complex, according to Penninx. Predator bugs are widely used, but regularly in combination with conventional means that are damaging to the predators and beneficial micro-organisms, making them less effective.

At the moment, according to Penninx, the strawberry cultivation still has sufficient conventional means. However, it is expected that the package of resources will shrink, while insect pests become increasingly resistant to the active substances. "Many commonly used fungicides, however, kill the useful micro-organisms in the soil or substrate, according to research by Koppert Biological Systems. In short, the way of conventional agents simply is ending."

In addition to the pest insects, there are soil pathogens and fungal diseases. Penninx: "I myself started to evaporate sulfur against mildew in 2011. But two years later I already stopped with it. Not only because the sulfur is potentially harmful to the employees, the substance also impedes the proper functioning of predatory mites. The perspective is very limited."

According to Michiel Penninx and Rob van Enckevort, who has two companies in America (Limburg) and one company in Kronenberg (Limburg), growers have to deal with insect pathogens, fungi and soil pathogens in a coherent way. "It has to be done quickly," he says, "otherwise we will run out of options. And then we should not be surprised if we, by growers or suppliers who start to mess up, have to deal with fipronil-like affairs with enormous damage to our image as a result."

The dark scenario that Penninx outlines is fed by the international competitive relationships. Competing countries such as Spain, Morocco and Egypt know very well how to produce quality strawberries.

"In the field of biological crop protection and cultivation sustainability, these producers have sometimes already taken a lead on the Netherlands," says Mark van der Werf. He is a consultant at Koppert for NatuGro, a package of products that brings resilience and nutrient intake to a higher level. "The competitive relationships also make it necessary for Dutch strawberry growers to quickly make their production more sustainable."

According to Van der Werf, plant resistance has a key role when it comes to making strawberry cultivation more sustainable. "But good resistance is the result of several factors that have to be aligned rather precisely with each other. Often that knowledge is available, but this knowledge is still too fragmented. This explains why the guidance so far was not good enough and why the cohesion between all kinds of measures is sometimes still hard to find."

In view of the above, the working group, or think tank, will bring together knowledge from different disciplines in order to work on a stronger crop. The five most important factors for a resilient crop are the climate, soil, fertilization, water and crop protection.

These fields of knowledge are all represented in the working group. The other members (in addition to Penninx, Enckevort and Van der Werf) are Jan Simons (advisor at substrate supplier Bas van Buuren), Toon Melis (advisor at horticulture advisory group Hortinova), Maikel van de Ven (advisor at research center NovaCropControl) and Bart Joosten (advisor at Mertens). Together they also look at Next Generation Growing and how that can promote plant health.

Meanwhile, the working group has met three times. The first goal is to reduce the use of fungicides against mildew and other crop diseases much further, if possible to zero. This must be done by means of a greater plant resistance. According to Michiel Penninx, that should be possible. "Mildew is currently our biggest challenge. Just because there are still enough fungicides against mildew on the market, which are also still abundantly used, mildew is the biggest obstacle to a more sustainable strawberry cultivation."

The working group now wants to exchange information during one year, compile knowledge and increase the insights. Perhaps also crop trials might be commissioned to research institutes. Mark van der Werf: "In a year's time we will see what progress has been made - what have we learned? - and what the priorities should be then."

Furthermore, other growers are welcome, says Michiel Penninx. "More growers in the group also means more practical experience and more exchange of experience. We can only benefit from a collective.”

Penninx does not doubt that the insights that the group is developing will find a way to practice. "After all, all relevant disciplines of the business sector are represented in our working group. The representatives of these companies will ensure that the latest knowledge will reach their customers quickly."

Penninx is convinced that there are sufficient possibilities to make strawberry cultivation more sustainable. "The range of predators and biostimulants has become very broad. For many problems there is already a sustainable solution. Now we have to go and learn how to optimally use all these products in combination with each other."

In his opinion, cultivation does not necessarily have to be completely organic or ecological. "Well integrated is also progress," he says, "even in that case the share of chemistry decreases. That is progress and that will be received well by society. Look at the rapid growth in the demand for and sale of organic products, in the Netherlands and elsewhere in Europe. The demand for sustainable strawberries is already there. But are we going to meet it or leave it to other countries?"