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Alternate resources and use the BOS system
"Continue to alternate and combine resources this season to maintain maximum control over phytophthora. And use a BOS system. This provides a well-founded indication of when and with what the control of disease has the greatest chance of success." This is according to Mark Ermers, product manager at Cebeco Agro and also a member of the Taskforce Phytophthora.
At the end of March, Bayer spoke to him. "We have had two horrible years. We must not let ourselves be surprised again."
To start with, a brief look back: how did phytophthora get so out of hand in recent years?
"First of all, this has to do with the weather conditions. These were – certainly in 2024 – quite favourable for the fungus. But we also made mistakes in controlling the disease, mainly due to the emergence of new phytophthora strains. This has not always been tackled nationally with the right resources and the right strategy."
How about that?
"For that we have to go back to the end of 2022. At that time we received signals from Denmark that the active substance mandipropamid (including in Revus*) had a strongly reduced effect on the new phytophthora strain EU-43. This was reason for us to change the usual block spraying with Revus in the advisory scheme for the 2023 season to other products and more variety in resources. A large part of our growers acted on this in time, but a large number of growers nationwide have continued on the old path - with block spraying - as a result of which not all phytophthora strains have been adequately controlled.
In 2023, there was also far too little attention paid to controlling phytophthora in the tuber, which resulted in many spores entering the soil. We saw the consequences of this in the spring of 2024. In combination with the wet weather, this resulted in a huge number of infection peaks. Fortunately, we still had reasonably sunny weather in August, which meant that we just avoided getting into trouble with the availability of resources. Furthermore, the message from the Taskforce – alternating and combining resources – was fortunately very well received last season. As a result, in my opinion, we escaped an outright disaster."
What is the starting situation regarding phytophthora this year?
"The starting situation regarding tuber phytophthora is better than last year anyway. So we are starting a little less restless in any case. As mentioned, alternating and combining agents worked well last season and it is now important to maintain this and refine it even further. An important tool for this is the colour scheme, in which each active ingredient group has its own colour. By using agents from a different group or 'colour' each time you spray, the risk of resistance breakthrough towards the agent package is significantly reduced.
I find the use of a BOS system just as important (decision support system). This not only provides you with substantiated advice for phytophthora spraying, but also sends you into the field at the best possible time to spray. Growers who use a BOS save an average of three sprayings per year, meaning that this system actually pays for itself in one year. I fully understand the criticism that BOSs sometimes advise to spray again after three or four days – which can sometimes be very difficult in terms of time. But you can also turn it around: take the BOS advice to heart and adjust the logistics to it as much as possible. This not only means that you spray at the best possible time, but you also spray more sustainably with a minimum of resources. The latter is also becoming increasingly important in the context of social discussions on crop protection."
Finally, a word about the resources: do we still have enough? And are they strong and diverse enough to keep phytophthora under control?
"We currently have six FRAC groups with preventive mechanisms of action and two with curative mechanisms of action (see also figure). If we can maintain this – with the associated resources – then we should be able to keep phytophthora well under control for the time being. As said: the most important thing is diversity in mechanisms of action, because that way we can also continue to tackle the diversity of the fungus well."
"An important tool in this context is InFinito. This is indispensable in every schedule because of its unique active group – fluopicolide. It works both preventively and curatively and the dosage is also very flexible. That makes it an all-round, multifunctional agent. Infinito can be used in the middle, but also at the end of the schedule, in both ware potatoes and seed potatoes. As far as I'm concerned, Infinito will also be in every rotation schedule next season."
Action plan/colour scheme for the use of phytophthora resources
*Revus is a registered trademark of Syngenta.
