Now that all the onions are indoors, the excitement of the growing season has subsided for a while. But in reality, cultivation requires attention year-round. In this article, onion expert Kees Jacobs discusses a few storage considerations and variety selection for 2026. He also discusses incidents with fusarium and new varieties for sand and clay.
"The onions generally arrived in the shed in excellent condition. I see many batches with a beautiful color and firm skin. And the yields are also excellent for most growers." Onion expert Kees Jacobs of Syngenta looks back on the 2025 growing season with satisfaction. However, he must also mention a small discordant note. "I'm hearing from the trade that more fusarium is being found than anticipated during the field period. It's being found in all onion regions, even in batches grown on soil where onions have never grown before. It appears to be a late infection. Optical sorters aren't yet removing the affected onions, the infections are so young. The cause isn't clear, but I wouldn't rule out the possibility that it's related to structural deterioration caused by heavy irrigation combined with the high average temperatures of last summer. Again, these are isolated incidents, but the trade is currently cutting more onions in half when assessing a batch than usual."
Using senses
Due to the relatively mild temperatures of the past few weeks, there haven't been many opportunities to cool the onions. Jacobs: "Most batches are now dry and therefore ready for cooling. We'll have a few colder nights this weekend and again at the end of October. But there's no extreme urgency to cool them. If you reach the target temperature around Sinterklaas, that's fine. You have to adapt to the season a bit."
Whether they're cooled or not, it's still important to keep a close eye on the crop, the onion expert continues. "Preferably several times a week, and use all your senses. What do they look like? Are they still rustling, or do they need a heater again? Or do you smell the pungent odor of bacterial rot?" Jacob's final storage tip concerns monitoring sprout dormancy. "Many onion plots unexpectedly declined rapidly at the end of the season. And then you're left wondering if there was sufficient growth after the MH spraying. Anyone who's unsure and wants to store the crop for a longer period, I advise to do a potting soil test starting in mid-November."
A potting soil test allows a grower to determine whether the MH spray has been effective and whether the onion has a good dormancy period. In mid-November, place about 50 onions in potting soil at a temperature of around 15 degrees Celsius and keep the soil moist. When the onions start to form roots after about three weeks, you, as a grower, know that long-term storage is not an option.
To sell or not to sell?
With the above-average yields that onion growers are achieving this year, the question arises as to what a smart sales strategy is. Jacobs has some ideas. "Exports are booming and are well ahead of previous years. With moderate prices of 13 to 14 cents, it's relatively easy for traders to find a market. And if you have 55 tons per hectare or more in storage, as a grower you already have a nice profit on the cost price. But it's anyone's guess what the future holds. If you have the option, I would create a pool myself by selling some regularly. Growers who have multiple cells or store in crates could consider this." Incidentally, Jacobs is concerned that there's currently hardly any price formation for red onions. He doesn't know if it's related, but according to Jacobs and many of his colleagues, the 35% increase in acreage reported by Statistics Netherlands (CBS) is far too high. "We haven't seen that reflected in the field."
News from the racial front
It won't be long before growers start thinking about their variety selection for 2026. Syngenta has some interesting news to share on that front. "We at Syngenta have recently been able to offer a few varieties specifically developed for sandy soil," says an enthusiastic Jacobs. "Starton stands out for its earliness. And Reflection is mid-early and scores very well on yield." With Revelation, Syngenta launched a new variety for clay soil last year, and it's showing surprisingly strong performance in practice. "This variety was originally selected for its excellent dormancy, but it also turns out to have a strong root system. With increasingly extreme weather, that's a distinct advantage," says Jacobs. Strong roots are also a characteristic of flagship product Promotion. "Not only does it last longer in drought conditions, but we're also seeing that Promotion is more resistant to fusarium and pinkroot in the field."
The seed availability of Syngenta's yellow varieties will not be a problem next year. The situation is different for the red variety Allurion: "It's been sold out for two years running, and we've been unable to build up stock in recent seasons due to weather conditions in the seed production regions. So, the availability of Allurion will be limited."
Next year
What the 2026 growing season will bring is still largely shrouded in mystery, but according to Jacobs, undisturbed growth is becoming increasingly important. "Next year, we'll no longer need Spiroteramat-based insecticides; this will make controlling thrips very difficult. But a well-growing crop is already a big win. Varieties with a strong root system will have an advantage. And for a smooth start, Syngenta will be adding new varieties next year." Promotion en Revelation A biostimulant applied to the onion seed, in addition to the usual disinfection with Maxim. Because the sooner the onion can get going, the sooner the vulnerable period will be over.