Fruit producers rely on nets for better harvests

By Christine RoTechnology of Business Reporter

2 hours ago

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Nets are being used more and more on fruit farms

It’s an elegantly simple solution to an age-old problem: to protect plants from danger, keep them covered.

Nets are commonly used to keep pests out in vegetable production, especially in high-value areas such as seed.

But in fruit production, the use of nets is still being researched and tested, according to Mirella Aoun, an agronomist and researcher at Bishop’s University in Quebec, Canada, who has been studying agricultural nets for over a decade.

Prof Aoun explains that fruit growers originally put nets over trees, mainly to protect them from hail damage. Now they are experimenting with nets that can protect against insects.

The mesh size of insect protection nets depends on the local conditions, including the type of insect.

Of course, that could exclude the insects farmers really want — pollinators like bees.

One option is to deploy the nets after the pollination period. Another is to open the nets during the day while hives are brought in.

Tree nets are particularly well established in French and Italian apple orchards, where nets draped over rows of apple trees restrict movement and oviposition of codling moths. This has helped farmers get rid of stubborn pests and reduce the use of expensive and polluting chemical pesticides.

There are benefits for fruit lovers too. “If you know you have less pesticide residues from crops that are under exclusion nets, that’s good news for consumers,” says Prof Aoun.

Networks are also seen as a means of countering the effects of climate change. Warmer conditions have seen resurgences in some species of insects and diseases.

Some regions are experiencing more intense droughts and heavy rainfall, and nets can help with that.

Depending on the location, type of netting and how it is used, a netting system can shield solar radiation that leads to heat stress and inhibits photosynthesis in trees.

But introducing a net could mean a wetter environment around the tree – not helpful for plants prone to fungal diseases in wetter climates like the northeastern US and Canada.

However, some researchers are working on hydrophobic webs, where a treatment with a botanical pesticide renders the webs essentially water-repellent.

Image source, American University of Beirut

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Nets mean less use of pesticides, says Mirella Aoun

Photoselective (colored) meshes can also influence the incidence of light. Dark, opaque meshes reduce light intensity but not light quality.

Pearl-colored nets are better at diffusing the light, allowing it to reach more parts of the vegetation. Meanwhile, blue, red and yellow meshes filter specific wavelengths of the sun and can thus stimulate specific responses in plants related to fruit quality.

According to Prof. Aoun, fine-tuning net usage often leads to an increase in high-profile fruit. As her research in the Mediterranean has shown, trees covered in colored shade netting can produce larger and more vividly colored fruit.

Networks are not always the solution. They may not be suitable for smaller, more varied orchards. They are also not required for all climate conditions.

Also, the netting used for fruit trees is usually made of polyethylene, which isn’t ideal for a world trying to break free from plastic dependency.

One of the companies working on nets without plastic is Texinov, a French technical textiles company. Texinov is researching different types of biodegradable nets, such as those made from flax.

It has already introduced a biodegradable polylactic acid (PLA) mesh made from fermented corn. Industrial composting is required to break down this type of net, which according to sales manager Adrien Etienne is around 10% more expensive than traditional nets.

Mr. Etienne says that the biodegradable nets are currently more popular in Europe than in North America. This may be related to European policies aimed at reducing the use of insecticides. “I think the nets are becoming more popular because insecticides are less popular,” says Etienne, for example with French cherry growers.

The initial cost has been an obstacle for some farmers. “Of course, nets are a bit expensive compared to insecticides,” admits Etienne.

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The mesh must be carefully calibrated to local insects

The cheapest Texinov net sells for around €0.50 (44 pence) per square meter for private use in France, according to Mr Etienne. This type of net lasts only one to two seasons, whereas the heavy climate protection nets can last much longer. Durability depends on factors such as sun exposure. “The sun makes the nets more and more brittle,” says Mr. Etienne.

Overall, Prof Aoun says prices are falling as products become more diverse and accessible. “In general, the positive effect of the network outweighs the negative side,” she summarizes.

Jean-Marc Rochon runs the Pépinière Rochon apple nursery in Québec and keeps tabs on the progress of netting.

“In my view, this technology is more in the development and improvement phase than in large-scale application,” he says.

For Mr. Rochon to use netting on his apple trees, the cost of the netting wouldn’t be the only factor. “I see it more as an opportunity to rethink how we operate,” he explains.

In order for his nursery to be profitable, the network had to be reliable and not cause work overload. It should also be usable on large orchard sections.

Of course, it will take technological refinements and communication to convince more fruit growers that nets would be useful.

But Prof Aoun believes: “As we increasingly approach climate challenges and unpredictable weather, protective cultivation with netting is the way to go.”