Insect pests are a real headache for farmers, particularly those wishing 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. Conventionally managed orchards, meanwhile, must rely on products that are harmful to the environment, and vegetable growers face numerous pests unless they use insect-proof netting to protect their crops.
Use of anti-insect nets
Insect nets can be used in greenhouses as well as in open fields, where they also protect crops against strong winds, hail and heavy rain. The nets can be laid directly on the crops, but vegetable growers prefer to use metal or PVC hoops to keep the net away from the plants, which allows better air circulation.
How to choose your insect netting
Several factors must be taken into account when choosing the insect net that suits your needs. First, identify the most problematic insects to determine the mesh size. The mesh opening must be smaller than the width of the thorax of the smallest pest you want to keep out. For example, for carrot or cabbage flies, you will need a mesh smaller than 0.8 mm.
The porosity of anti-insect netting is also a key factor in ensuring healthy plants. The more porous the netting, the more air it lets through, drying out plant leaves more quickly, reducing the risk of disease and avoiding sudden temperature rises.
Light transmission is the third factor to consider. Depending on the materials used, the nets let through 64% to 92% of the light. Less light can benefit some vegetables but can be harmful when maximum light is required.
Finally, crop rotation must be carefully planned to prevent larger species from becoming trapped under the nets, and nets must be installed in a very airtight manner, as many pest species have a knack for finding loopholes to squeeze through.
The cost-effectiveness of anti-insect nets
Insect nets have an average lifespan of 5 years if they are handled and maintained with care.
Organic apple growers in Eastern Canada see yield losses of around 50% when they do not use netting. Nets help achieve higher crop yields and better fruit quality, making organic operations competitive and viable. A study by Quebec’s Ministry of Agriculture, Fisheries and Food (MAPAQ) under the Prime-Vert program, which aims to increase the adoption of agri-environmental practices, showed that a gain of one bushel per tree unit could be enough to cover the extra cost of using single-plot nets for apple growers.
The same goes for vegetable growers. A March 2014 report by Christine Villeneuve, vegetable horticulture advisor at Quebec’s Ministry of Agriculture, Fisheries and Food, indicates that an additional annual income of only $375 per 80 m tunnel or greenhouse is enough to recover the cost of materials and labour for installing insect nets.
This report also includes a table showing the mesh size required for each type of pest.
Sources:
Anti-insect netting or how to keep insects away from your vegetables
Christine Villeneuve, vegetable horticulture advisor at Quebec’s Ministry of Agriculture, Fisheries and Food.
March 2014
EVALUATION OF SINGLE-PLOT NETS FOR THE PROTECTION OF APPLE TREES AGAINST INSECT PESTS WITHOUT THE USE OF INSECTICIDES.
Mirella Aoun, agr., Ph.D., for Quebec’s Ministry of Agriculture, Fisheries and Food under the Prime-Vert program
February 2016
It can be downloaded here.
Exclusion nets for organic apple production in Eastern Canada
Gérald Chouinard et al.
Dalhousie University
February 2017
It can be downloaded here.
