Beating fungi without chemicals - how Vromans does it with Serenade |
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Fully green: Vromans switches to Serenade for fungal control
Keeping fungi under control using a fully green strategy? It's possible, as Vromans Nurseries in Biest-Houtakker (N-Br.) demonstrates. In recent years, the company has extensively tested the biological product Serenade—and it's paid off. This past winter, shrub and conifer cuttings were treated exclusively with Serenade. "The results have been so positive that we're now making a full switch to Serenade," says operations manager and partner Geert-Jan van der Heijden.
| Geert-Jan van der Heijden (right) is operations manager and partner at Vromans Nurseries BV in Biest-Houtakker (N-Br.). The company specializes in shrubs and conifers, growing over 300 varieties (as cuttings, in pots, and in open field). Vromans Nurseries covers approximately 100 hectares: 3 ha under glass, 16 ha container fields, and 85 ha open ground cultivation. The company employs about 40 permanent staff year-round. Iwan van der Steen (left) is a technical-commercial advisor for nurseries at Kiemkracht. |
"Right now, it's a bit of a messy period. The cutting section is full, we're starting a new round of potting, and planting out cuttings in the field has begun. Everything is overlapping, which takes some extra attention," says Van der Heijden. Despite the hustle, he takes time to review crop protection strategies with regular advisor Iwan van der Steen from Kiemkracht. "Fortunately, we've had a reasonably good spring so far, with a faster start to the growing season. Sales also started on time, so we've been able to spread out the work nicely," he says, referring to the dreadful late 'horror spring' of 2024.
Van der Steen also notes that this year has been much more manageable than last season, although the relatively dark winter with few hours of sunlight has led to higher fungal pressure in the cuttings. "We're seeing that now in the rooting process—it's lagging slightly compared to previous years."
Preventive measures
The company first tries to prevent fungal infections (from, among others, Pythium and Botrytis) through preventive (cultivation) measures. Van der Heijden gives several examples, such as early morning venting of cuttings under plastic. "By briefly rolling up the plastic in the morning, we've seen a significant drop in fungal issues." Another method is growing in double trays (one inside another), creating 1.5 cm of "air space" beneath the roots. "This makes the plants less susceptible to infections like Pythium and Phytophthora," the manager explains.
Drainage design on the container fields also supports preventive disease management. The fields are built in a roof shape (a slight slope), so excess rainwater drains to both sides toward concrete paths. "After heavy rainfall, the paths may briefly flood, but water is directed via pipes to a retention pond for reuse. This way, plants don't sit in water, fungi get fewer opportunities, and we also prevent runoff into surface waters," says Van der Heijden.
The company also tries to use crop protection products preventively and sustainably. But this is a "very tough" and sometimes "impossible" challenge, both men acknowledge. Van der Steen notes the loss of key (chemical) tools for controlling dieback in conifers. "It's especially difficult to manage this disease in Juniperus species during summer." Mite control (in outdoor crops) has also become harder due to the loss of certain products.
Van der Heijden knows all too well that this can lead to reducing or even discontinuing certain crops. "Not long ago we were growing over a million boxwoods. Now, due to box tree moth and Cylindrocladium, we're down to about 90,000. That's partly due to declining consumer interest, but also because we simply can't control the pests and diseases anymore."
Experience with green products
While Van der Heijden is concerned about the loss of important chemical tools, he also sees an exciting challenge in testing and using green (biological) alternatives. He says he's been working with plant strengtheners, biostimulants, and biological products for at least 25 years. "I haven't counted, but I think we've tested at least 30 green products here. Only four or five actually lived up to their claims—the rest didn't deliver."
One product that did meet expectations is Serenade. Van der Heijden has been using it for at least ten years. "We started in the greenhouse with a trial on Osmanthus, an evergreen shrub. This crop is quite dense and has high fungal pressure in winter. We compared Serenade's fungicidal effect to a conventional chemical schedule. Since there was no difference in plant health between the two approaches, we continued using Serenade in propagation."
Full switch to Serenade
Now, ten years later, Serenade is used in nearly all shrub and conifer cuttings on the nursery. This past winter (mid-November to mid-February), the company used Serenade exclusively as a preventive measure against fungi—with no additional chemicals.
Van der Heijden explains that the product is applied both to the soil (for Pythium, among others) and as a foliar spray (for mildew, leaf spot, Botrytis, etc.). "We start with a soil application and water it in. A few weeks later—depending on crop development—we move to foliar applications. With one product, we can control all key fungal diseases."
Advisor Van der Steen says this fully "green" approach reflects strong confidence in Serenade, although he emphasizes that the product must always be applied preventively and consistently every week. "The key is to keep the crop healthy. Once disease sets in, Serenade won't help anymore and you'll need to resort to chemicals." According to Van der Heijden, that's only happened once in recent years—during a stretch of prolonged wet weather. "We might still hit a bump now and then, but the results with Serenade are so positive that we're now fully committing to a green strategy," he concludes.
This article was originally published on April 3, 2025 on the Boom In Business website.
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