Millerandage

Its most common cause is cold, rainy or otherwise bad weather during the flowering stage of the vines though other factors, such as boron deficiency or fanleaf degeneration, may also play a role.

For other varieties, such as Pinot noir or the Mendoza clone of Chardonnay, wine quality could be improved due to the reduced overall berry size and higher skin to juice ratio.

While this is most often attributed to bad weather, other factors such as nutritional deficiencies (particularly of the mineral boron which is needed to synthesis the growth hormone auxin and facilitate the movement of sugars in the vine) or viral infections can play a role.

Since grapevines are hermaphroditic (containing both male and female parts) and usually rely on self-pollination, the presence of wind to circulate pollen or insects usually doesn't influence the success or failure of the pollination stage.

In some areas, such as the New World wine regions of Australia, California and New Zealand, the presence of millerandage in the a vineyard can be seen as a positive quality for a vintage due to the reduced average berry-size.