Choice of mesh size usually depends on three factors
1. They type of pest, or pests, you wish to control.
2. Your ability to manage any changes to orchard micro climate that may occur after netting the orchard (nets with smaller mesh sizes have a great impact on the orchard microclimate than nets with larges mesh sizes).
3. Financial factors: Nets with a small mesh size are more expensive than large mesh nets. In addition, they are heavier and some can hold hail (and therefore may need stronger, more expensive structures to support them).
Net with a 40mm mesh size will exclude larger birds (such as lorikeets, parrots, crows, ducks), but smaller species (such as silver-eyes) will only be excluded by nets with a mesh size of 15mm or less.
Net panel widths should coincide, if at all possible, with tree row widths or multiple of these. Panels are usually 10-15m wide but can be wider. Wider nets are generally favoured where available as they reduce installation costs because there is less joining, however very wide nets can be difficult to handle when erecting. With flat canopy designs, panel widths greater than 10m may require a support wire down the centre of the panel to reduce sag.