Rain makes the difference in weed pressure in onions

Weeds require extra attention from the participants of the Boerenbusiness Crop tour onions. Not everywhere there was a lot of rain last week and that is why soil herbicides sometimes work less effectively. That calls for additional measures to keep the weeds under control.

Rain has a big influence on the effectiveness of soil herbicides, says Jacky Dieleman, grower in Philippine (Zeeland). "We haven't had much rain here. As a result, the soil products don't work optimally. Enough weeds are coming through. This week we want to use a contact product for the second time."

His colleague from Zeeland, Klaasjan Boer, a grower in Kortgene, had a total of 18 millimeters of rain at the end of last week. "The soil products are doing their job. Because some of the seed on some plots was initially dry, we have not sprayed Wing P yet. Everything has germinated in the meantime," he explains. "This morning we carried out a contact spraying for the third time. We will repeat that at the end of the week. After that I expect the second batch of onions to come up, but then we will be largely clean."

Wary of Roundup via spot sprayer
Hubert Linders from Nederweert (Limburg) also shares his experience: "Ten days ago we applied soil herbicides. Yesterday we applied the first contact spray. For the time being we do not need a spot sprayer." The use of a spot sprayer to apply a broad spectrum herbicide (such as Roundup) is becoming increasingly popular for controlling weeds such as ground-keeping weeds.

Reinder Hogenhout from Kimswerd (Friesland) notes: "The first potato growth is starting to appear above, so I expect to use the spot sprayer next week." An important consideration when using Roundup is the possible collateral damage to the onions. Wilbert Lindhout, Commercial Promoter at Groot en Slot, is quite concerned about this: "I remain wary of Roundup. There is no vapour effect under a hood, but you want to be sure that the onions are not affected." Reinder responds to this matter-of-factly: he indicates that he achieved great results last year with the spot sprayer in combination with Roundup against potato growth. "With the spot sprayer, fewer onions are killed than when you manually tap the potato growth with a selector", according to Reinder. "Due to the high dosage of Roundup, you quickly have damage both above and below ground with a selector."

Different approaches in practice
Arjan Jakobs from Wezup (Drenthe) has also used various methods: "In the cradle stage I tackled the weeds thoroughly with a contact spray, then with soil herbicide at the first pipe." This week the second contact spray is planned to clear up some dog parsley. "Soil herbicides did their job, we had a total of about 50 millimeters of rain after sowing. That helped a lot," he adds. Jacobs wants to use the spot sprayer at the end of May to tackle the stubborn weeds. Jan Berend Biesheuvel from Zeewolde (Flevoland) has also applied soil herbicides twice and carried out a spraying with Roundup just before emergence.

Mechanical weed control is also used by some growers. Reinder Hogenhout did a round with the weeder last weekend, which requires precision. 

The onions on Arjen Jacobs' plot from Wezup already form beautiful rows.

The onion plot of David de Wit from Lepelstraat

The onions on the plot of land of Jan Berend Biesheuvel from Zeewolde also grow in a straight line.

The onions of Peter Holster from Marknesse

Weed control on the onion plot of Reinder Hogenhout from Kimswerd

The onions from Aeres Farms Dronten are just coming up.

© DCA Market Intelligence. This market information is subject to copyright. It is not permitted to reproduce, distribute, disseminate or make the content available to third parties for compensation, in any form, without the express written permission of DCA Market Intelligence.