Covered growing is winning terrain

Within fifteen to twenty years, indoor cultivation will have gained a permanent foothold in the cultivation of hard fruit, expects FruitSecurity Holland. According to the company, the reasons for this are the advance of exotic insects and the impoverishment of the pesticide package. A condition is that the market is willing to pay a premium.

By: Ank van Lier, freelance journalist, fruitteelt@nfofruit.nl

In recent years there have already been experiments with growing apples and pears under plastic roof systems, to protect the fruit from precipitation and thus prevent mould. Experiments with this are being conducted at Proeftuin Randwijk, among other places. Gerben van Veldhuizen of FruitSecurity Holland expects the cultivation of hard fruit under plastic covers to take off. "The impoverishment of the pesticide package is forcing growers to look for other ways to combat moulds. Foil covers, which prevent the fruit from getting wet, can be an effective tool. A condition, however, is that the plot is only covered at the top; the sides must remain open. Otherwise, there is a good chance that problems will arise with other types of diseases and pests." At the moment, according to Van Veldhuizen, covers made of woven film are mainly used, because the necessary experience has already been gained with them in cherry cultivation. "The advantage is also that woven film is incredibly strong. Tunnel film or blown film stretches under the influence of heat, which reduces the tension. This type of film is also more easily damaged. According to Van Veldhuizen, automated covers that can be slid open and closed are the best option for cultivation. "After all, with them you can grab the maximum amount of light and thus achieve optimum production. However, such a system is also more expensive - how much more expensive is difficult to say - than a fixed foil covering, which costs about five euros per m2. The grower will have to recoup this investment somewhere. A higher yield price is really the only option, especially since society wants fruit growers to work more sustainably. And you can make a lot of demands, but there has to be something in return. The main challenge we face as a sector is to hold this discussion and to achieve a better price. And the outcome of this discussion will also determine whether or not foil tapping will continue in hard fruit."

Packing with hail nets

In addition to film covers, Van Veldhuizen expects hail nets to play a more prominent role in the cultivation of top fruit. He already sees that, in Austria and Italy among others, more and more apple and pear plots are being 'wrapped' with hail nets. "This has everything to do with the advance of exotic insects, such as the brown-marbled shield bug. To protect apples and pears against this, growers completely pack their orchards with hail nets, both on the top and the sides. And from a cultivation point of view, this is also perfectly possible, since hail nets have an open structure and there is sufficient ventilation." According to Van Veldhuizen, the market will probably play a less decisive role in the advance of hail nets, because the investment is more limited than with foil covers. "For 1,500 to 2,500 euros, you have a plot completely 'netted'. Also the fact that several club varieties require an investment in hail nets and include it in the payout price will contribute to a further expansion of this." For a combination of rainfly and insect netting, such as is used in cherry cultivation, Van Veldhuizen sees few opportunities in hard fruit cultivation. "It would be too tight, which would limit ventilation too much. Moreover, in the cultivation of hard fruit there are still few insects that are so small that hail nets do not provide sufficient protection." FruitSecurity anticipates that in the future, ever higher technical requirements will be set for both hail nets and film covers. "Due to climate change and more extreme precipitation, we will have to build the shelters in a different way. The anchoring and the structure need to be balanced and able to offer sufficient resistance, even during a heavy downpour." According to Van Veldhuizen, this does not mean that the systems will necessarily become more expensive. "By widening the anchor distance, for example, you can already make the system a lot stronger.And such adjustments will be necessary anyway, since insurance companies are also setting increasingly higher requirements for both hail nets and film covers."

`COVERED HARD FRUIT CULTIVATION HAS YET TO PROVE ITSELF'

"Placing film covers over hard fruit plots is a good idea in principle," responds WUR researcher Rien van de Maas. "It is not for nothing that we are testing a system with a 'cabrio hood' at Proeftuin Randwijk. This foil cover remains open in dry weather and can be closed when it rains. Van der Maas also expects that covers that open and close automatically will offer the best prospects. "With a roof, you solve many disease problems, but the chance of mildew and apple aphid increases. However, we think these problems will be less with automated canopies." The researcher emphasizes that the covered cultivation of hard fruits still has to prove itself. "How does the production develop in the longer term? Do other problems perhaps crop up? We still need to get a clear picture of all these issues. The required investment is also an issue. As Van Veldhuizen points out, these costs will probably have to be paid by the market. But we are also investigating whether this method of cultivation can be financed in other ways."