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Conviso has become a mature system
"Conviso has developed into a mature weed control system for sugar beets in recent years. Growers see the benefits and want to continue using it," says Lisette Staal, sugar beet account manager at KWS.
Bayer spoke with her about her experiences with Conviso and its future prospects. She expects the system to continue to grow in the coming years.
First of all: how big is the Conviso cultivation in the Netherlands now?
Last season, we sold around 8.500 units (packs), representing over 8.500 hectares. That's about 10% of the beet acreage. This share is expected to rise further in the coming season, reaching 10.000 units. We sold around 4.700 units of the Smart Liesa variety in the early order alone. That's considerably more than last year. So, growth is far from over.
Which areas offer growth opportunities for Conviso cultivation?
"We're mainly talking about the Veenkoloniën and the Eastern Sandy Area, especially Limburg. In these areas, weed pressure is relatively high, and growers often struggle with weeds that are difficult to control. These areas also have a considerable number of larger beet growers. For them, the Conviso system offers convenience; with two sprayings, you can control the weeds, and the timing of the spraying is also less critical than with conventional weed control systems. We've also seen growth in Zeeuws-Vlaanderen in recent years, where Conviso is primarily used to control things like dog's parsley."
To what extent have beet growers mastered the Conviso system?where lie the risks, pitfalls and misunderstandings?
Determining the first spray date remains a key issue. The beet growth stage is not the determining factor – as with the traditional system – but the stage of the host weed, which in practice is usually goosefoot. The rule of thumb is that this weed should be in the 2- to 4-leaf stage at the time of the first spray. This is when you can expect the best results. The second spray can then follow about ten to fourteen days later, during which time you should take into account the effectiveness of the first spray and the status of any germinating weeds. This can sometimes mean that it's better to spray a few days later. This is usually not a problem; Conviso One has a soil action time of between ten and twenty days after application, which is longer than that of conventional herbicides.
"It is also important that a mixing partner – usually Betanal Tandem – and oil is always added to Conviso One. This is to prevent weed resistance to ALS inhibitors."
We also emphasize that growers remove all existing bolters. If you leave them standing—and they form seed—they're virtually impossible to remove in subsequent crops (where ALS inhibitors are also frequently used).
We also remind growers to carefully distinguish between regular and Conviso seed. Those using both systems on their farm should thoroughly clean the seed hoppers of the seeder and the sprayer tank between uses. We also recommend a buffer strip of several meters between regular and Conviso beets. This prevents a few rows of regular beets from being washed away in the event of a slight drift.
Are two sprays of Conviso One always sufficient?
Yes, in principle. Although there are a few weeds on which the product is less effective. Veronica species in particular, including speedwell, are not sufficiently controlled. And emerging orach is also not always sufficiently controlled. For these weeds, adding 0,5 l/ha of Betanal Tandem + oil (phenmedipham & ethofumesate) is necessary. A pre-emergence spray can also be applied.
Furthermore, there is a very limited area where some resistance to ALS inhibitors has developed over time. This often concerns chamomile, goosefoot, or groundsel. The growers in question usually know where these areas are and in that case, they do not opt for Conviso cultivation.
From Conviso One It's known that active ingredients can remain in the soil for extended periods, potentially causing damage to subsequent crops. What are the latest insights in this area, and how can growers prevent damage?
It's crucial to perform proper tillage after growing Conviso beets. This means plowing deep enough so that the topsoil is no longer present. This is sufficient for growing potatoes. However, there is still a risk for fine-seeded crops like onions and carrots, and for tulip bulbs; therefore, we advise against growing these crops immediately after Conviso beets.
Which varieties will KWS have available for Conviso cultivation next year?
For the coming season, we have the well-known Smart Liesa KWS variety available in the rhizoctonia segment. Due to weather conditions at our production site in Italy, there is little or no seed available for two other varieties – Smart Blomma KWS and Smart Jutta KWS. This is a real shame, as both varieties score highly on the Recommended Variety List for financial yield (99 and 97) and resistance to rhizoctonia. We hope to be able to supply these varieties in abundance in the 2027 growing season. Smart Jutta KWS, in particular, is a real asset. This variety possesses triple resistance: to rhizomania (supplemental), rhizoctonia, and beet cyst nematode. This represents a significant step forward for us.
Until now, under Cosun's direction, a "No, unless" policy has been implemented regarding the Conviso system. As a result, Conviso cultivation has grown in a regulated manner. What are your thoughts on this?
As a company, we ideally want to move full speed ahead with our SMART varieties. The "No, unless" policy has certainly put a brake on that. But we also see advantages to such regulated growth. In recent years, for example, we've been able to provide the right support to advisors and growers, particularly regarding the aforementioned risks of the system. This has not only led to better and more comprehensive advice regarding Conviso, but has also protected us from mistakes that are sometimes made in countries with faster growth.
Finally, what does the future hold for the Conviso system?
As mentioned, we expect further growth. In the Netherlands, this could easily reach a quarter of the acreage or even more, given the high level of interest among growers. The benefits of Conviso cultivation are clearly visible in practice. In that respect, we don't need to push anything; the growth will more or less happen naturally.
