On the 11th of January 2022, the LNCN held their annual National Onion Day in the Netherlands, due to current circumstances this edition was held online this year, instead of in Dronten. The edition was divided into 3 parts, where different subjects were discussed. In the second part, attention was paid to fungus and weed control in onions, where expert Erno Bouma was present
Biggest challenges in onion cultivation in 2025
Online attendees could answer real-time questions, to join in the conversation. When chairman Mark Brandjes asked what the biggest challenge would be in onion cultivation in 2025, most people answered ‘fungus control’, with insect control in second place and weed control last.
Weed control in onions
Evert Hofman of Agrifirm joins this session to explain the possibilities in weed control. He indicates that there are currently many possibilities in terms of mechanical weed control. He indicates that by applying hybrid weed control (combination of chemical and mechanical), many chemical agents can be saved. He indicates that he does not believe in a solution without chemicals, but less is certainly a solution. The application of chemical agents should be well adjusted to the weather, for example, because of the degree of water solubility.
Controlling fungi without Mancozeb
Erno Bouma has been invited by the LNCN to share his vision on the possibilities of fungus control in onions without Mancozeb. Because of the disappearance of this agent, the choice of agents is even more limited and fungus control becomes a complicated factor. Erno indicates that he believes it can be done, but that it will be difficult. Erno says: “With the right choices and variation of agents, it is possible to protect the onions well. However, the help of a BOS-system (decision supportive system) makes it a lot easier.
“It’s easier to keep up-to-date, because a climatic sensor like the FieldMate always provides you with the conditions in the field.”
– Erno Bouma
Viewers’ question
One of the viewers wonders how accurate a BOS system is, especially when the weather station that provides the weather data is located far from the company. Mark Brandjes adds that he can imagine that the location of the weather station has a big effect on the outcome of the BOS system, so that it might as well spray regularly by calendar. Erno indicates that these are valid questions, but that this is easily solved with the inexpensive weather stations that are available on the market today. The FieldMate is one of these affordable solutions, which has the advantage that it has to be placed in the field. By receiving measurements from the field, you have a clear picture of the disease pressure in the field.
Spraying by calendar
After Erno Bouma’s explanation of the BOS-system, Mark Brandjes wonders if 10 to 13 sprays still doesn’t look a lot like calendar spraying. He wonders if this is because of the absence of Mancozeb, and whether a BOS system is of added value in this way.Erno disagrees: ” Spraying by calendar comes from the potato cultivation, where we used to spray every 7 days against one disease. The example mentioned in the onions concerns 10-13 sprayings throughout the season against multiple diseases. Erno also sees the BOS system as an added value, because when a downy mildew infection is detected in the field, the infection has already occurred 10 days earlier. By working with a climatic sensor in the crop, one can see in advance whether the conditions for an infection are favourable or not, so that it is possible to take preventative action.
Conclusion by Mark Brandjes
Mark Brandjes concludes at the end of this part that: “If you want to continue growing onions well in the future, and such a challenge exists, you need to invest. Either in a BOS system, or in mechanical weed control to be able to compete professionally in onion cultivation in the future.” To which Evert and Erno nodded in agreement.
