'Smooth finger grass remains the major challenge'

"Smooth-finger grass will remain leading for the time being in maize weed control. But morning bindweed, cranesbill and also potato storage are advancing a bit every year, so we have to be more and more aware of that." That is what contract worker Marcel Klein Rot from Buurse (Overijssel) says. Every year he sprays about 900 hectares of maize. Together with maize specialist Sander Uwland from Bayer, he looks back on the 2022 maize season – and also ahead of the 2023 season.

Marcel Klein Rot is an experienced man when it comes to weed control in maize. "I've been doing this work for about forty years, so I know most of the plots in the area," he says during a conversation at the kitchen table. Klein Rot sprays about 900 hectares of maize every year, which amounts to about four hundred different plots in Twente and the Achterhoek. He sprays most plots himself with a relatively new trailed Horsch LT 4 with GPS. But son Stef likes to help with a somewhat older CHD sprayer. "He then does the well-known, straight pieces. I do the more difficult plots," he explains the 'division of roles'.

According to Klein Rot, knowing the plot history – and therefore also the weed density – is crucial for targeted weed control (and choice of resources). "I have an overview of most plots in this area. And if new ones are added - such as this year the 150 hectares that I received from a colleague contractor who is retiring - I always check the condition of those plots beforehand and what kind of weeds to expect."

'Smooth finger grass is represented on almost every plot here'
The weed control went well last year, the contractor looks back. "We started on time, so we didn't have to rush anywhere. And luckily, after a dry start, a few showers came on time, so the resources worked well." Sander Uwland of Bayer also indicates that few 'accidents' have happened in the maize, although according to him there were quite a few germs (especially Meldes) that were clearly visible during the harvest.

When asked about the biggest challenge in weed control, both men 'obviously' put smooth-fingered grass forward. "Smoothfinger grass is represented on almost every plot here. Although it doesn't actually grow that big, it can form an extremely dense mat and it draws a lot of moisture and nutrients away from the maize. Many growers are not aware of this." , says Klein Rot. He therefore tries to persuade growers to opt for (additional) pre-emergence control with Frontier®, especially on plots with a lot of smooth-fingered grass. "That costs a few tens more per hectare, but you benefit a lot from it. You get a cleaner plot in return and in many cases a higher yield, although the latter is very difficult to prove..." According to Uwland, it would would help a lot if maize growers at the end of the season would not only look 'up' at the cobs, but also 'down' at the weed cover. "What about weeds then? Which species? And how massive are they? Make a note of that and discuss it with the contractor who comes to spray the following year. That makes sense anyway." Klein Rot also notices that growers see many 'dead threads' of smooth finger grass between the rows during the harvest. But the realization that about six weeks earlier these were a thick green mass and have already formed seed for next year, that is not always there. According to Uwland, that is also the creeping danger of this weed. "Growers often think: hardly any grass can grow under fully grown maize, so no smooth-finger grass either. But it does. A sown mat like that can remove so much moisture and nutrition that it just saves half a meter of maize."

Mix for sowing and undersowing
With regard to the choice of resources, Klein Rot is advised by three different suppliers. "Their basic advice is often the same, but on details - and then it often concerns additions - they usually differ slightly", is his experience.

Last season, the contract sprayer made one standard mix for undersowing (on approximately 40% of the plots) and one standard mix for re-sowing a catch crop (on approximately 60% of the plots) - with the option of additional pre-emergence spraying with Wing® P immediately after planting. sow. 

For undersowing, a broad mix was chosen last year with 0,15 l/ha Capreno + 0,5 l/ha Calaris® + 1,25 l/ha Laudis + 0,25 l/ha Milagro® + 1 l/ha Robbester . "We were able to get the plots clean with this, even if there was a bit more smooth finger grass," says Klein Rot. When asked by Uwland why Frontier Optima was left out of the mix, he replied that the risk of damage to the catch crop is too great for him. However, Uwland indicates that the addition of a soil herbicide can clear up a great deal of slippery grass and that – under normal circumstances – the risks of serious damage to the catch crop are small. "My advice would therefore be: clean up smooth-finger grass as best you can - and if necessary, opt for early maize varieties and reseed a catch crop to clean dirty plots."

Laudis as an alternative
Last year, 0,2 l/ha Capreno + 0,5 l/ha Calaris + 0,3 l/ha Milagro + 0,4 l/ha Frontier + 1 l/ha Robbester were chosen as the spray mix for re-sowing a catch crop. "We were also very satisfied with that; we did an excellent job of clearing up all the weeds that occurred," says Klein Rot. Uwland notes that since last year Calaris® may only be used once every three years – and then also in a lower dose (maximum 50%) than before. According to him, it will be very difficult to benefit from such a label. "In particular, the rapid effect against meldes, but certainly also the big plus on cranesbill and smooth-finger grass will be absolutely missed. So we will have to compensate for that as much as possible next season with adjusted doses or other means," he says. As an option, he pushes forward the combination of Laudis (1,75 l/ha), Monsoon Active (0,75 l/ha) and Frontier Optima (0,4 l/ha). In addition, (an increased dose of) Laudis ensures a very broad effect on weeds - and thus also compensates for the loss of Calaris. Monsoon Active mainly offers extra power on grasses and root weeds and Frontier Optima provides the necessary soil effect. "Our experience is that this mix works excellently on maize fields. Anyway, of course you hear that from a Bayer man," he laughs. 

'Preferably combinations with Capreno'
Klein Rot indicates that he has not yet made a choice of means for next season, although he indicates that he will no longer use Calaris for the sake of simplicity and the prevention of administrative errors. He also tends towards combinations with Capreno (with a slightly increased dosage), because these have also worked well in the past year. According to Uwland, this is also possible - with the same mix as last year, but without Calaris - especially if the experiences with this drug are simply good. 

Klein Rot likes to take all considerations during the conversation to the upcoming meeting with his advisors, but at the same time likes to steer his own course. "After forty years of spraying maize, I know quite well what resources should be used for a good result," he concludes.

^{Calaris® and Milagro® are registered trademarks of Syngenta
Frontier® Optima and Wing® P are registered trademarks of BASF}

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