Pollination bags, sometimes called crossing bags, isolation bags or exclusion bags, are containers made of various different materials for the purpose of controlling pollination for plants. Characteristics of pollination Bags Pollination bags are designed to fit well over the inflorescence or individual flowers of a plant type. The size, shape and strength of bag should ensure that there is no contact with flowers to avoid development of diseases and physical hindrances in seed development. The size of bag will vary with the size of inflorescence to be covered. Pollination bags may be 2D or 3D. The 3D bags have a gusset for expansion to avoid contact between the plant and the bag. Sometimes pollination bags may have a window to allow examination of inflorescence without removing the bag. Bags with a flap over the window, when provided, protects from strong sunlight. Most pollination bags are produced by general paper bag manufacturers which have branched out into providing pollination bag supplies. Such bags may not suit to the needs of plant breeders of different crops. Some companies such as PBS International UK, Del Star (Delnet) Technologies (Delnet bags) and Focus Packaging manufacture customized bags of different qualities for individual needs. Modifications in bags have been made that allow pollen collection without opening the bag in order minimise contamination. These bags have provision on one side that allows attachment of a plastic tube in which pollen can be collected after shaking the bag. Bags for female flowers sometimes have nozzles for introducing the pollen without any need for them to open. Plant breeders have often faced a problem of opening of bags at the seams. Glued seams do not hold long under variable weather conditions frequented with rains. Pollination tents are also used for controlled pollination. Design of pollination bags Good pollination bags are those which have most of the following properties: Enough strength against abrasions and tearing by wind, rain storms and birds in the open field or water spray in the glasshouse. Highly effective barrier to pollen grains with pores smaller than the size of pollen. Allow sunlight penetration for continuation of photosynthetic activity within the bag. However, the material should be UV stable. Moisture and air should be able to pass through the bag. There should be enough aeration that should not let temperature rise drastically. Rainwater should not collect in the bag and rain should not deteriorate the