It is still early, and the main part of the seed onions still needs to be harvested, but an initial indication shows that the 2024 harvest year will not be a top one for the seed onions. Up until early August, many growers were expecting a decent yield. Ultimately, the lack of regrowth has resulted in average kilos. "False mildew is the biggest merchant," it sounds.
"We see that the early fields have died off quickly this summer, which ultimately costs yield significantly," summarizes advisor Paul Hooijman of Delphy. In his work area (Central Netherlands), this is largely due to the impact of false mildew, 'but that phenomenon is visible nationwide,' he knows from his colleagues. Kees Jacobs from seed supplier Syngenta also confirms this. "Roughly speaking, the further you farm from the coast, the higher the mildew pressure. You have less wind and more shelter around a field, which keeps the crop wet longer."
However, onion experts along the coast also see mildew wreaking havoc in the onion fields. "We know that with a long leaf wetness period, mildew becomes a problem earlier," says Arjan Bos of Hazera. "Precisely these fields are often sown early, causing mildew to occur early. Heavy showers before harvesting have also accelerated this process."
Large variation
At the end of August, the harvest of seed onions has started well in all parts of our country. The spread is large this season, partly depending on the sowing dates. Onions were sown in March, but also well into May. This results in the digging and loading taking place at widely different times. "Some late fields have not even started to die off yet," Jacobs observes. "This could be due to heavy weed control, causing the onions to stand still for a while at the end of May and beginning of June. Problems with soil structure and low nitrogen availability are also mentioned as reasons for disappointing growth.
Throughout the country, fields can be found that simply do not want to die off, as noted by Bart Schriever of De Groot en Slot earlier on Boerenbusiness. Whether mildew can also cause an unpleasant surprise in storage is still guesswork. "Fields that do not die off but are still dying off can, with a heavy rain shower, encounter bacteria," explains Jacobs. In addition to the mildew issue, which is more difficult to control due to the absence of the fungicide Mancozeb, the onion experts also see stemphylium causing premature leaf die-off. "You have to be on top of disease control," Bos sees. "That means starting in time and not stopping too early. Where that didn't go quite right, you see the consequences immediately."
Varying yields
It is still early to make definitive statements about the yields. Johnny Remijn, advisor for Delphy in Zeeuws-Vlaanderen, estimates 35 to 50 tons per hectare. "The yield variation is not only due to the sowing time," he explains. "Drought also plays a role. Many fields have therefore been irrigated at least once." Currently, harvesting on clay soil is also largely at a standstill because the ground is too hard. Growers are hoping for a rain shower. Arjan Bos also sees significant variation in the north of the country. "We see fields of 45 tons, but also outliers much higher. On average, the onions are finer this year, as the plant count is not everywhere as expected after losses this spring. Also, due to fewer growing days, the onions have not grown as large."
On the trial fields of Syngenta, Jacobs sees yields ranging between 50 and 60 tons gross. "This surprises me, considering the emergence and plant count," Jacobs explains. "Growers in East Brabant and North Limburg, who have already delivered their onions from the field, are expressing similar sentiments. Due to the very high temperatures, harvesting could no longer take place in this region from Wednesday onwards, to prevent sunburn." Locally, hail has also caused some damage at the end of August. In eastern Flevoland and around Emmen, harvested onions have sometimes even been hailed in the swath.
MH spraying
The rapid die-off not only impacts the yield but also raises concerns about quality among insiders. Particularly, doubts arise about the absorption of MH on fields that have died off early. After spraying with this sprout inhibitor, you need two weeks of active sap flow. "It is good to monitor questionable batches closely in storage," says Hooijman. "If no sprouting is visible in November, then it's fine. If not, these batches will not store well for long." Fusarium infection is less common in his work area this year than in recent years. "We know from experience that a late infection in August can cause a lot of trouble, but because the first half of the month had relatively moderate temperatures, this will hopefully not be too bad."
It is difficult to say what percentage of the seed onions has been harvested so far. It is estimated to be around 15% to 20% of the total area. Depending on the weather, growers hope to make significant progress this week. This makes the harvest feel slightly ahead compared to other years. "One is quickly bringing in their onions before the predicted thunderstorms, while another is waiting for the rain," notes Bos. "It is important to thoroughly inspect the batches. We regularly come across rotten onions. On fields with a poorer structure, fusarium is visible. An onion affected by fusarium also does not evaporate moisture, so proper drying in the shed is definitely required."
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