'Spraying against Cercospora alone is not enough'

"If we want to keep Cercospora under control in the coming years, we will have to do more than just spray against it," says Henk Maalderink, arable farming specialist at Agriant and agricultural field service employee at Cosun Beet Company.

In addition to a more 'cercospora-oriented' choice of varieties, he advocates a broader use of the BAS app. "Because with that you always get reliable and targeted spraying advice." For the important first spraying, he recommends using the strongest agent. At the moment, that is Propulse.

"Yes, the problems with cercospora are still increasing here in the eastern Netherlands. And yes, every year there are plots that completely fail as a result of the disease." Henk Maalderink does not beat around the bush: cercospora is and remains a 'headache disease' on the eastern sandy soils. The fact that many growers are now spraying it four and sometimes even five times to keep the fungus under control does not change that - unfortunately. "We will really have to do more to keep the disease under control in the coming years. Spraying against it alone is simply not enough."

Construction plan and variety selection
A first, systematic option to suppress cercospora is a broader construction plan. "As far as I'm concerned, that is at least 1-in-4 and preferably even broader. The longer it takes for the beet cultivation to return to the same plot, the more breakdown of cercospora spores", says Maalderink. Due to the obligation of rest crops within the CAP, he already sees a slight trend towards a broader rotation.

A second way to keep cercospora under control is through the choice of varieties. Maalderink explicitly advocates the use of varieties with a high score for leaf health. "In this area, that should be at least an 8, but preferably a 9, the so-called CR+ varieties." To illustrate, he shows a photo of two frequently sown varieties - one with an 8 and one with a 9 for leaf health - next to each other. Both varieties have been treated exactly the same, but the difference is visible on the line: the variety with a 9 is much greener than the variety with an 8. "In practice, we see that the CR+ varieties are healthier and therefore yield more sugar. So it is worth growing such a variety in any case."

According to him, sowing varieties with a 7 or less is asking for trouble. "Unless you are certain that you want to harvest the beets in September, that is really not recommended. Cercospora tolerance should be at the top of the list when choosing varieties, especially on the eastern sandy soil."

Beet heap not on beet land
The location where the beets are laid after harvest can also be an important source of infection, Maalderink knows. "In this area, most beets are dumped on headlands and then loaded with a beet mouse. A few years later, beets are sometimes grown there again and you can see from the line where the beets have been lying; that is very often where you see the first cercospora infections." According to the advisor, this can easily be prevented by dumping beets on a fixed location or on a plot where there are no beets in the rotation. Finally, he also recommends properly incorporating beet leaves. "This measure also ensures that you do not carry any spores with you to the next growing season."

'Use a BAS app'
When spraying against cercospora comes up, Maalderink first mentions the Beet Advice System (BAS). "With this tool, you as a grower get very reliable and targeted spraying advice against leaf diseases at the right time," he says. In his working area - which includes approximately 2.000 hectares of beets - roughly a quarter of the plots are currently 'covered' with the BAS system. "That could be a lot more in my opinion. At the moment, a lot of action is still based on feeling. I don't want to say that this is bad, but we see every year that you make a more targeted, and therefore better choice with the BAS app," he says.

The timing of the first spraying is particularly essential. The advisor knows that whoever picks the optimum moment will immediately deal a heavy blow to Cercospora and can best keep the disease under control. But a BAS stake in the crop can also be useful late in the season. "A few years ago, we still advised not to spray after mid-September, but that advice is now outdated. Just look at last season, when the disease pressure continued well into the autumn. With the BAS app, you can keep your finger on the pulse until the end of the crop."

Getting Started with Propulse
As far as the choice of agents against cercospora is concerned, Maalderink believes the following rule applies: always start with the strongest agent and then alternate with other triazoles. "At the moment, Propel the most powerful agent against cercospora. Our advice is to start with that, possibly with the addition of a copper-containing foliar fertilizer for reinforcement. Because Propulse can be applied twice per season, the third spraying can also be carried out with it."

Although Maalderink indicates that a new, strong agent like Propulse is extremely welcome in the 'toolbox', he emphasizes again that spraying against cercospora is no longer sufficient. "We will have to seize all possible measures in the coming years to keep the disease under control."

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