Insect screen systems improve greenhouse climate in tomato cultivation

SchermNed, a family business based in the Westland region of the Netherlands, has installed insect netting in greenhouses for many years. Even so, results from the field can still surprise the specialists, as has been the case in tomato cultivation, where a growing number of growers are installing the company's insect netting filter systems.

At growers such as Wim Peters Kwekerijen, greenhouse climate remains stable even during summer conditions. For a long time, concerns about reduced ventilation capacity kept growers from installing netting at all, says Jack van der Voort of SchermNed. "Our research shows a maximum temperature increase of just one degree Celsius. Tomato growers have no trouble with that at all. In practice, we're now even seeing that the temperature build-up is often much lower than that." Van der Voort points to measurements taken at Wim Peters Kwekerijen, a tomato grower that switched its entire 30-hectare production area to the insect netting filter system in phases. The grower opted for greenhouses with frameless roof vents fitted with SchermNed's system, which has a mesh size of 0.77 x 0.77 mm. "Across our 30 hectares of tomato greenhouses, we were surprised by the minimal impact, just 0.3 degrees, after phasing in the SchermNed insect netting filter system," says Wim Peters.

Insectengaas bij Wim Peters Kwekerijen

Air and Light

About a decade ago, SchermNed commissioned research into the system's effect on greenhouse climate and air exchange. Dutch research organization TNO compared the system with a greenhouse without insect netting filter and one fitted with accordion-style screens. "Ours came out on top," says Van der Voort, who notes that SchermNed supplies all four of the most common netting systems on the market. Following the encouraging results from tomato growers, Van der Voort revisited that earlier research. It confirmed what SchermNed had long known, but what remains little known among many tomato growers. "Our insect filter system is being installed more and more often, but plenty of growers still aren't familiar with it."

The system was originally developed by Van der Voort's father. Since then, it has been further refined and, according to the Naaldwijk-based screening and insect-netting specialist, can now be applied in greenhouses worldwide. "The shape and volume of the insect netting largely determine the climate effect," Van der Voort explains. Growers use the system to keep unwanted insects out of the greenhouse in an affordable and environmentally friendly way, while retaining beneficial insects inside and maintaining an optimal climate. The insect filter system can be installed in new greenhouse builds as well as retrofitted into existing structures. "One advantage is that it doesn't require any changes to the ventilation mechanics, since our system doesn't put additional load on them," says Van der Voort. Because the insect netting filter is fitted on the inside of the vent, growers can continue ventilating during rain or frost in winter months when they need to remove excess humidity, a particular advantage in illuminated crops such as tomatoes, Van der Voort notes from experience in the field. "Many growers want to test our system in practice first. Once they do, we often see them stick with the insect netting filter system as they scale up."