Chemical synthetic pesticides are needed to produce high quality fruits. However, the use of pesticides is put more and more into question in Switzerland. Therefore, there is a need for alternative measures to protect orchards from pest insects and fungal diseases. One possible solution to reduce the amount of applied insecticides are side nets to exclude pest insects. To investigate the influence of these nets on pest insects and the microclimate, Agroscope started in 2012 a long-term research project with the varieties Opal and Milwa-Diwa. Out of 16, eight tree rows are only covered with a hail net, whereas the other half is additionally enclosed with a fine-meshed side net from full bloom until harvest. Since 2016, the effects of the side net on pest and beneficial insects, fruit growth, the photosynthetic activity, the amount of fruits harvested, the fruit quality and the microclimate are measured.
First results indicate that side nets successfully protect apple orchards from pest insects without influencing temperature or fruit quality at harvest. However, undesirable side effects may occur as a consequence of increased humidity and reduced wind speed in plots with side nets. If leafs and fruits remain wet for a longer time, fungal infections may increase. This would require additional applications of fungicides compared to plots without side nets. In 2017, therefore, we will also measure if fungal infections are increased in plots with side nets than in those without.
In 2018, a new model orchard with the varieties Gala and Bonita was planted. In addition to side nets to exclude pest insects, we will also install a rain cover to reduce fungal infections and thereafter hopefully apply not only fewer insecticides but also fewer fungicides.