Fusarium has appeared in varying degrees this year, both in the polders and in Zeeland, and indeed in all growing regions, according to reports from the trade. Generally, the infection only emerged later in the growing season. It's not a particularly Fusarium-infested year, but a surprising number of reports of infected onion batches are still being received.
Rumors in the trade suggest the fusarium problem is remarkably widespread this season. Several samples were tested nationwide, and fusarium was found everywhere, even on virgin soil where onions had never grown before. The conditions of the recent period were favorable for the development of the fungus. Fusarium thrives in warm, moist conditions and can spread rapidly at soil temperatures between 17 and 25 degrees Celsius. In the north, where more rainfall has fallen and the soil has remained moist for longer, the problem is therefore more pronounced.
Fusarium strikes
Although the fungus is widespread, this doesn't mean every plot is equally affected. It wasn't visible at all growth stages in the plots. Often, the onions appeared healthy at harvest, but for the past week or two, we've seen fusarium clearly emerge in some batches. Market reports indicate that the degree of infection varies considerably: in some cases, only a few onions are affected, while in others, more than ten percent of the batch is affected. One trader says he's even seen batches where more than twenty percent is now infected, though he calls these exceptional situations. "You can still dry out a few percent," he explains, "but with ten percent or more, you have to ventilate so much that you're causing the good onions to wear out too quickly." Fusarium doesn't spread from onion to onion in storage. Everything that's already infected remains in that onion. However, the fungus, initially latent in some onions, can later become visible and cause damage.
According to an industry sales expert, the fusarium problem cannot originate from the seed. "Fusarium is not transmitted through seed. Moreover, the seed used for onion cultivation is routinely coated with a fungicide, making it virtually impossible for the fungus to enter the fields that way." He explains that the source of the infection is in the soil. "Fusarium can survive in the soil for years as resting spores, even if onions are temporarily not being grown. As soon as conditions are favorable, for example, sufficient moisture and a soil temperature between 17 and 25 degrees Celsius, the fungus can suddenly become active and attack the onions. So it's primarily a matter of environmental factors and crop health, not the seed."
Tight supply boosts prices
The trade is also taking the fusarium virus into account. Many requests are coming in for good quality onions, it is said. Lots with high tare weight are difficult to process without electronic sorting. Because the trade is well aware of the problems, they are being more cautious about buying and selling. Partly because of this, but also in general, the market is becoming tighter. Buyers are having to offer higher prices to replenish their stocks. In a rising market, this means that the selling prices of sorted onions will also have to increase to maintain margins.