"The climate in the greenhouse is exactly what I had hoped for," states René de Bakker when asked about his first experiences with insect netting. In March, the Dutch chrysanthemum grower had SchermNed's insect mesh filter installed at one of his three locations. In mid-July, the grower was already seeing what he wanted to see: "On the hot days we did have, it didn't get hotter in the greenhouse with mesh than in the one without."
Maintaining ventilation capacity
Two years back, Gebr. Nederpel started thinking about investing in insect netting. "We looked at harmonica netting, as you see a lot in vegetable greenhouses. However, we thought it was a disadvantage that the temperature in the greenhouse would then be a bit higher. In our opinion, we would miss ventilation capacity anyway."
After coming into contact with SchermNed, the choice fell on their insect mesh filter. At that time, the growers had also heard experiences from colleagues, including those of a nursery, and a company that wanted to keep moths out. "Both companies were very positive. Their crops are different, but they have the same problems. We could make good use of their experiences."
Keeping lice and thrips out
In the pot chrysanthemum greenhouse, lice and thrips out are the two main pest problems. "There are increasingly fewer products that can be used, so you have to look at how you can keep these little critters out," René concludes soberly.
In terms of mesh size, the choice fell on 0.27 x 0.77 millimeters. "The standard size," indicates Carl Stougie, sales manager at SchermNed. "It is the size that many growers can work with." Insect netting is not yet widely used in pot chrysanthemum greenhouses. Nevertheless, here, the entire greenhouse was screened off. Carl: "That gives a better indication than when you start testing in one or a few departments."
The pot chrysanthemum grower uses the insect mesh filter to keep out aphids and most of the thrips. "If thrips fly in with their wings open, they won't enter our greenhouse. If you want to keep all thrips out, it's better to keep the windows closed," he laughs.
Rainy spring
SchermNed installed the insect mesh filter. The installation required opening the energy screen of the greenhouse. As soon as the outdoor climate allowed, the installers could get to work.
It has been a bit quieter than other years in terms of pest pressure due to the rainy spring and the continued absence of prolonged summer weather in mid-July. With the large amounts of rain and dark weather, it was more humid than normal, though. Neverthless, after several months, René is pleased to conclude that the insect netting is doing what it is supposed to do.
More importantly, he's also happy with the greenhouse climate. "I am very happy with the air movement under the netting, and that we have air exchange. We noticed that, and I also see it reflected in the data of the climate computer." He does feel that moisture lingers a little easier in the greenhouse. It helps that already invested in dehumidification systems. Without those dehumidifiers, however, would he also have dared to choose insect netting? "Yes," says René confidently. "But the fact that we already had dehumidifiers makes it easier."
Poinsettias
One of Gebr Nederpel's three sites has now been netted off, with the help of a piece of subsidy. In about three years' time, René hopes to have netting installed at all locations. Because the location with mesh is next to one without, René can make good comparisons. "A few weeks back it did get really hot for a while. Then the temperature rose in both greenhouses, but it didn't get hotter in the greenhouse with an insect mesh filter. It is just as cool as in the greenhouse without mesh."
Next winter, Gebr. Nederpel will also grow poinsettias again. During the winter, the grower, who likes to maintain a temperature of 18 degrees Celsius in his greenhouse, does not air much. In terms of insect pressure, he expects to make a big step when it comes to whiteflies. That is a challenge in poinsettias. "Currently, white fly pressure is low, and I expect that insect netting also helps to keep the pressure down much easier. That way, we may also be able to save costs on biological control."
For more information:
SchermNed B.V.
+31 (0)174 62 22 14
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www.schermned.nl