Insect nets to reduce pesticide use

June 20, 2022
Insect pests are a major issue for farmers, especially those who want to obtain organic certification. For example, in Canada, due to the dozens of pest species that damage crops, the supply of local organic apples is very limited despite growing demand. Apple and produce growers following conventional practices use products that are harmful to the environment to deal with pests. Instead, insect netting can be used to protect their crops.

Use of insect nets
Insect nets can be used in greenhouses as well as in open fields, where they also protect crops from high winds, hail and heavy rain. Nets can be installed directly on crops, but produce growers prefer to use metal or PVC hoops to keep the netting off the plants, allowing for better air flow.

How to choose your insect net
Several factors must be taken into account when choosing the right insect net. First of all, you need to identify the most problematic insects in order to determine the mesh size. The mesh size of the net should be less than the width of the thorax of the smallest pest that you want to block. For example, for carrot or cabbage flies, you will need a mesh of less than 0.8 mm.

The porosity of insect nets is also an essential factor for healthy plants. The more porous the net, the more it allows air to pass through, allowing leaves to dry out more quickly, reducing the risk of disease and avoiding sudden rises in temperature.

Light is the third factor to consider. Nets can let in from 64% to 92% of the light, depending on the materials used. A decrease in light levels can be beneficial for some plants, but detrimental for those that require maximum light.

Lastly, you need to plan the rotation of the crops to prevent larger species from being trapped under the nets. And make sure there are no gaps in the netting, because several species of pests are very good at finding their way in!
The profitability of insect nets
Insect nets have an average lifespan of 5 years if handled and maintained with care.
Organic apple growers in Eastern Canada see a 50% yield loss when they don’t use them. Nets lead to higher crop yields and better fruit quality, making organic production viable and competitive. A study by the Quebec Ministry of Agriculture, Fisheries and Food as part of the Prime-Vert program, which aims to increase the adoption of environmentally friendly practices in agriculture, showed that a gain of one bushel per tree could be enough to cover the additional cost to apple producers of using multi-row nets.

The same goes for produce growers. A report from March 2014 written by Christine Villeneuve, a horticulture advisor with the Quebec Ministry of Agriculture, Fisheries and Food, indicates that it only takes $375 in additional annual revenue for an 80 m tunnel or greenhouse to recover the cost of the materials and labour to install insect nets. This report also includes a table showing the required mesh size for each type of pest. It can be downloaded here.

Sources:
Les filets anti-insectes ou comment garder les insectes à distance de vos legumes (Insect nets or how to keep insects away from your vegetables). Christine Villeneuve, horticulture advisor at the Quebec Ministry of Agriculture, Fisheries and Food. March 2014.  It can be downloaded here.

Évaluation de filets monoparcelle pour la protection des pommiers contre les insectes ravageurs sans utilisation d'insecticides (Assessment of multi-row nets for protecting apple trees against insect pests without the use of insecticides). Mirella Aoun, agr., Ph.D. for the Quebec Ministry of Agriculture, Fisheries and Food as part of the Prime-Vert program. February 2016.  It can be downloaded here.

Filets d’exclusion pour la production biologique de pommes dans l’Est (Exclusion nets for organic apple production in the East). Gérald Chouinard et al. Dalhousie University. February 2017.  It can be downloaded here.


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