Weed mats need to be thick enough to be able to prevent light from reaching the soil. Even the slightest sliver of light can start germination, which will cause weeds to grow.
Anti-insect screens protects plants by exclusion. Some nettings can also contain additives that help to increase their effectiveness against pests. Newer types of mesh netting can include optical additives such as aluminum strips for light reflection.
In recent years, numerous crops have been found to improve their productivity and fruit quality when grown under colored (photo-selective) shade nets.