Lately, a persistent soil fungus has gained ground in the Dutch greenhouses: Fusarium. This disease is found in many open-field crops, and has already caused a lot of damage in Italy, Japan and the United States.
Renting extra
The greenhouses from Carlo de Jongh’s Slacollectief have been safe from fusarium so far. Carlo tries to keep the disease away by preventing contamination where possible: “First, we have the barrel washed at the nursery, before lettuce plants are grown in it. We also ensure that no goods from affected growers come here.” The grower does acknowledge that the lettuce sector now has quite a problem with fusarium: “Growers need to rent extra greenhouses to be able to meet the contract cultivation.”
Throwing away harvest
Ees de Winter of VOF de Winter is also no stranger to the fungus disease. “Several growers have already stopped growing greenhouse lettuce in the summer months. In the long run, this could lead to a shortage of lettuce,” Ees says. “Fusarium is a worldwide problem in many arable, vegetable and flower crops. Fusarium in lettuce was mainly predominant in Portugal, Italy and the United States at first. Because of our more moderate temperatures, we thought the Netherlands would be able to dodge the bullet. But unfortunately that’s not the case. Some growers had to throw away nearly their entire harvest. We are working hard on finding a solution.”
Economic suicide
According to Ruud van Amersfoort of Horti-Consult Int., the Netherlands is only really starting to feel the problems with fusarium now: Eight companies in the Netherlands have been seriously infected by the fungus. At half of these companies, growing butterhead lettuce is economic suicide. The acreage involved is about 8,5 hectares. The consultant says a few of them have stopped growing butterhead lettuce in summer, trying to balance out the production plan with other crops. “There is one grower, for instance, who has swapped 3 hectares with a radish grower’s land. That’s because the radish isn’t affected by the disease. Of the remaining 4 companies, steaming has taken place at a third of them already, a second will steam about 3,000 m², and another grower is having his entire company (3 ha) steamed, which means he will be out of action for 7 weeks.”
Prevention
For now, prevention seems to be the only method: “With 70% of the acreage affected, the grower has to switch to a different crop. The greenhouse then becomes so heavily affected that steaming probably isn’t a solution anymore. With a much lower degree of infection, steaming will suffice though. And the work will have to be done very hygienically. So spraying off tillage and planting machine first at the yard, before allowing them onto the recently disinfected soil. That also applies to all the materials in the greenhouse, by the way, like plant breeding trays, shoes and harvesting trousers. Keep everything separate for clean departments,” Ruud says.
Overcropping
Incidentally, Ruud sees a decline in head lettuce in retail: “I’ve seen less and less butterhead lettuce on shelves in particular in the last five years. On a tight market, large quantities of butterhead lettuce have been grown below the cost price for years. This applies to the entire horticultural sector, by the way. The lettuce sector needs to ask itself if they haven’t overcropped their land in recent years. This, as well as that monoculture, facilitates diseases. It’s the same with people who’ve been cropped up inside for too long. Ultimately it becomes a hotbed for illnesses.”
Carlo de Jongh: c.de.jongh1@casema.nl
Ees de Winter: ees@vofdewinter.nl