Insights from Frank Janssen, R&D Manager at Grodan
Since 2022, a limited number of high-tech greenhouse pepper growers worldwide have faced a rapid and severe form of wilting that posed a threat to crop production. This has left growers searching for answers.
In response, Grodan funded rigorous, independent research, collaborating with a wide range of industry partners to analyse all potential contributing factors. Findings to date currently point to a specific isolate of the pathogenic fungus Fusarium as the cause. Today in the Netherlands and Belgium the isolate it is referred to as Fusarium oxysporum radicis capsici (FORC). In Canada it is referred to as Fusarium Oxysporum Species Complex (FOSC). It is highly pathogenic and specific to peppers. Initial scientific reports also show that wilting caused by the Fusarium isolate can occur in both stone wool and organic substrates.
In the following Q&A, we ask Grodan’s R&D Manager, Frank Janssen, to discuss ongoing research efforts that Grodan is conducting, and what growers can do while we work together towards more definitive solutions.
What does the science say so far?
“Following the initial outbreaks in pepper crops exhibiting sudden and severe wilting in Europe independent scientific studies were commissioned in the Netherlands (Glastuinbouw Nederland / Normec Groen Agro Control) and in Belgium (Proefstation voor de Groenteteelt in Sint-Katelijne Waver). These studies identified and named the Fusarium isolate Fusarium oxysporum radices capsici (FORC) as the pathogen responsible” says Janssen. “Simultaneously outbreaks of pepper crops wilting with the same symptom expression also appeared in Canada. There researchers at Agriculture and AgriFood Canada identified and named the cause due to Fusarium Oxysporum Species Complex (FOSC).” adds Janssen.
How is Grodan contributing to scientific research into pepper wilting?
”We’re taking a two-pronged approach to address the knowledge gaps through research”, Janssen goes on to add.
“Firstly, we have initiated several scientific studies which are being managed by independent organisations such as the Wageningen University Research (WUR) and Botany BV in the Netherlands. We are also conducting trials at Vineland Innovation & Research Centre in Canada. These trials are focused on understanding potential infection pathways for the Fusarium isolates and also their level of resistance to current available plant protection products”. In these trials Grodan defines the research questions and experienced plant scientists design, execute and report the trials outcomes. So far, we have found that infection and symptom expression can be obtained in both stone wool and organic substrates”. Janssen goes on to say that “observations indicate that it’s easier to infect young plants in propagation or shortly after planting rather than older established plants. However, these are mere observations”, he emphasises.
“Secondly, we’re also participating in a number of consortia trials where we are investigating broader research questions together with other suppliers of substrates, seeds and greenhouse systems, as well as laboratories, government bodies and advisors”. Janssen goes on to add, “One consortium includes around a dozen commercial pepper growers who have suffered pepper wilting first hand, giving us the opportunity to closely analyse all aspects of their operation including their irrigation and substrate systems”.
Conducting research is nothing new for Grodan. As part of innovating new products and driving the substrate industry forwards, Janssen has personally been involved in countless trials for many different crops. “In my 19 years at Grodan I always select competent partners and set up a team of specialists with the right expertise”. Importantly I always leverage our extensive research network to bring in relevant knowledge from previous trials” he says. Going on to add: “The seriousness of this issue is why we’re simultaneously running trials in Europe and Canada leveraging a vast network of research specialists because it’s important to remember that these symptoms previously described by growers and researchers are not confined to only one growing region”.
Frank adds, "We also work closely with our customers, ensuring that the insights we gather directly support our ongoing research. When growers have questions or seek deeper collaboration, they know they can always reach out to their trusted Grodan contact person for tailored support."
What are the results and initial conclusions from this far-reaching research program so far?
“So far all of the available scientific evidence points to FORC or FOSC as a primary factor in pepper wilting in Europe and Canada respectively. In the research conducted with WUR, using the FORC isolate from Belgium and in Vineland Innovation & Research Centre using the FOSC isolate from Canada, we’ve seen that inoculation causes pepper wilting both in plants on stone wool and on organic substrates”.
“Moreover, our research observations suggests that it is easier to obtain symptom expression following artificial inoculation in young plants (inoculated in propagation) compared to older plants (inoculated after second setting)” comments Janssen.
”We’re also focused on investigating which factors may aid the infection pathway. One such investigation is the role that root quality plays. Here we’re investigating the impact that dosing different concentrations of disinfectants such as peroxide are having on root quality as well as the pathogenicity of the fusarium isolates. For example, at a certain (lower) concentration of peroxide we could see (under the microscope) root damage, but the pathogenicity of Fusarium is unaffected. In this case we would expect to see wilting. On the other hand, at higher concentrations, we could see root damage but also control over the Fusarium isolates. In this case we would expect to see no wilting due to Fusarium or observe wilting in response to increased environmental stress and plants may recover afterwards”. This suggests that while peroxide can suppress the pathogen at higher doses, the associated root damage must be managed carefully.
Our message to pepper growers
“Due to the complex nature of pepper wilting, there are currently no clearcut solutions about the preventive measures growers need to take and ensure no pepper wilting. As always, we recommend that growers maintain excellent hygiene during propagation and cultivation and take opportunities to thoroughly clean the greenhouse during crop rotation.”, states Janssen.
Frank concludes by stressing, “by collaborating with scientific experts to conduct multiple international studies into various possible factors involved in pepper wilting, we commit to supporting pepper growers worldwide by providing evidence-based insights to guide their decision-making. We will continue to share our research findings and fine-tune our advice to growers accordingly”.
