Vegetable news: WPK checks greenhouses step by step for optimally clean cultivation

Source: Groentennieuws

“Tholen – Department by department, plant grower WPK is enclosing its greenhouses in Made. In this way, the plant grower wants to keep diseases and pests at bay. With the air vents slightly ajar, a white fly or louse usually wants to blow in. With insect screen filters under the ventilation windows, Wim in ‘t Groen has much less trouble with this in Made.

Exactly as was the intention when WPK, the company of owner Erik van der Arend, approached SchermNed in 2020. “We were initially looking for a solution for growing cucumber and pepper plants,” says Wim. He is manager of cultivation in Made. “We gained customers from the United Kingdom. They are very strict there with whitefly checks. That was a reason for us to ensure a clean cultivation. With mesh we mainly want to keep aphids, tobacco and greenhouse whiteflies out.”

There are no moving parts with an insect screen filter from SchermNed. The whole thing is attached to the rod with an aluminum strip.

Gauze popular

Immediately in 2020, a first department of approximately 3,500 square meters was screened off with mesh filters. The choice fell on insect mesh with a mesh size of 0.27×0.77 millimeters. Carl Stougie, sales manager at SchermNed: “This is 90% of the cases in which the choice falls in greenhouse horticulture.”

One summer, a test was carried out by fencing off a department. WPK used measuring boxes and data loggers to look at what the installation of mesh did to the greenhouse climate and pest pressure. In recent years, installation of mesh in greenhouse horticulture has taken off. Before that time, growers were often somewhat reserved. Growers were unfamiliar with what installation of mesh would do to the greenhouse climate. “We are now seeing growers installing insect mesh in more and more crops,” says Carl. “In gerberas and cucumbers we see that as soon as the first growers opted for mesh, more growers followed.”

Good test

Wim now knows from his own experience that the insect mesh filters under his ventilation windows in greenhouses with a leg height of 4.5 meters have little effect on the greenhouse climate. “We started measuring in the first department and were able to make a good comparison with the other departments. When we superimposed the graphs, we saw no differences in temperature and absolute and relative moisture content.”
Last hot summer was an extra good test for WPK. “There was one week with very high temperatures and little wind. Then the climate felt a little less good,” says Wim. “It was extreme, but still no reason not to install mesh.”

In terms of pest pressure, WPK sees a lot of difference between departments that are meshed and those that are not, even if they are only separated by a rolling facade that goes up occasionally. “We scout much less whitefly in the sections with mesh. This makes it clear to us that a lot of this involves flying in through the air windows. There appears to be much less horizontal movement in the greenhouse.”

The mesh filter is adjusted depending on the size of the window.

Install yourself

Before WPK opted for the installation of mesh, they looked at other growers. “We went to production growers with cucumbers and peppers who work with the same type of mesh. We also see the results they saw.”

The choice for insect mesh filters was simple. Carl: “This is the best option for existing greenhouses. You also have concertina mesh, but you see that a lot in new-build greenhouses. You can fit it in well there. In existing greenhouses you have varying glass sizes that you have to take into account.”

Carl Stougie and Wim in ‘t Groen. WPK works with two screens. Light has also been considered when installing the insect screen. Carl: “The light reduction is limited and no more than with glass, about 15%. In addition, without gas, if you open the door, the sun has free rein and local combustion can occur. A mesh filter under the glass can help.”

After the test in 2020, another department followed in 2021. There are now six and the seventh department is coming. At WPK they do the installation themselves with their own people. Carl: “It’s not rocket science either. We provide a manual and instructions.” Wim: “We have good people and we also keep a close eye on how the installation is done.” You can also clean the mesh yourself. Wim: “For this we spray the dirt onto the greenhouse roof from the inside. The deck washer then does the rest.”

Carl knows that the first tomato growers among the production growers have now also started working with insect netting. “We delivered the first windows here at the end of last year.” Wim also knows a tomato grower who now works with insect netting. “He saw it with us and is now growing with mesh on ten hectares.”

WPK itself does not yet use it in tomato cultivation. “Tomatoes are grown slightly cooler, so you need enough air exchange. For us, with the good results we are now seeing, it is also worth considering in tomato cultivation in the long term.”

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