Tips for a healthy start to the new season
Thorough cleaning and disinfection are key to getting the new growing season off to a successful start. Paying attention to detail during this process can make a significant difference. During crop changeover, hidden risks often lurk in areas that are easily overlooked. For instance, pathogens from diseased or infected plants could linger in the greenhouse structure or gutters. Thorough cleaning and disinfection are therefore crucial for eliminating any potential sources of infection and ensuring a healthy, productive start for the new crop.

First clean, then disinfect
In many Dutch greenhouses, all plant material and substrates are removed at the end of the growing cycle, but polythene and ground coverings are sometimes left in place ready for the next crop. Before beginning the disinfection process, it’s essential to remove all weeds from the greenhouse. If possible, remove weeds manually or mechanically rather than using herbicides. If herbicides are necessary, opt for a contact type that has no residual effects. 

We recommend thoroughly cleaning the greenhouse after removing all materials and before applying disinfectants. While some growers prefer to clean and disinfect simultaneously, this method may not result in all surfaces being completely cleaned. Disinfectants are less effective on dirty surfaces, which can harbour pathogens that could cause problems later on. Additionally, we suggest keeping the temperature in the greenhouse at at least 15°C during disinfection, as disinfectants work more effectively at higher temperatures.

Dripper tubes
When disinfecting dripper tubes, which are often left in place during cleaning, there are several key points to consider. One method that is used for drippers hanging along the gutters with the pegs facing downwards is to fill them with disinfectant in situ. However, some growers prefer a different method: they remove the pegs with the tubes from the main dripping line and immerse them in a large tank filled with an acid solution. This way, all the tubes are disinfected at once and any limescale buildup on the stakes is dissolved. However, this approach does not fully remove organic contaminants. If soiling is still visible, it may be necessary to treat the hoses with a peroxide solution. 

Our experts emphasise that it’s important to pay particular attention to the interior of both the drippers and the supply pipes. “Always flush the pipes with disinfectant multiple times until the water runs clear. At the start of a new crop cycle, skipping this step can result in dirty water being used in the first irrigation. This can cause problems, so it’s crucial to devote sufficient time and attention to this task.”

Potential source of disease
Our experts stress the importance of keeping an eye on the area around the greenhouse. “Weeds often grow outside the greenhouse, and it’s not unusual to see old plant material piled up nearby. These decomposing materials can easily be blown into the greenhouse, potentially introducing pathogens.”

Our specialists also highlight the need to check drain reservoirs and other water storage areas. “Over time, a layer of sludge can form at the bottom of reservoirs, containing organic and other contaminants. These could be drawn into the irrigation system, posing a risk to the plants. To prevent this, it’s essential to thoroughly clean the bottom of the reservoir once a year. Crop changeover is an ideal time for this as the crop isn’t being watered then.” Regularly emptying and cleaning reservoirs has the added benefit of maintaining better oxygen levels in the water, supporting overall system health.

Strict hygiene practices after cleaning
Once the greenhouse has been thoroughly cleaned, it’s crucial to follow strict hygiene protocols: “Any equipment or materials brought into the greenhouse must be clean and disinfected. In fact, we recommend restricting access to the greenhouse until the new plants are in place. Additionally, all cultivation tools, such as harvesting carts and other equipment, must be cleaned and disinfected before being returned to a greenhouse that has just been cleaned and decontaminated.”

Hygiene tips for crop changeover: a quick guide

• Remove weeds from the greenhouse before cleaning. 
• Begin by cleaning with water and a brush or high-pressure washer, then disinfect.
• Block the gutter drainage points during disinfection to prevent disinfectant from entering the reservoir.
• For best results, make sure the ambient temperature is at least 15°C during disinfection.
• Thoroughly flush the dripper pipes and supply lines until the water runs completely clear.
• Inspect the area around the greenhouse for pathogens, such as decaying plant material, and remove any potential sources of contamination.
• Remove sludge from the bottom of drain reservoirs once a year to prevent any buildup of harmful contaminants.
• After decontaminating the greenhouse, make sure only clean and disinfected materials are brought back inside to prevent the reintroduction of any potential contaminants. This includes all tools, equipment and supplies.