We net the vineyard for protection reasons. It is the same concept, if you net or protect fruit trees with sun-ripened ready fruit. Birds of all kinds (even domestic chickens), and wildlife such as raccoons, coyotes, can feast on a vineyard and in some cases quickly eat your entire crop for the year. We have heard of vineyard owners who had their unprotected vineyard crop eaten in a weekend. Please note, netting is a good practice and economical for backyard vineyards. Commercial wine regions that have acres and acres of vineyards are not usually netted.
Netting is a simple way to protect your harvest. The optimum net size is the entire length of a grapevine row plus two feet extra per end post to cover end posts. Nets are rolled out along side the grapevine row. Thrown over the row of grapevines, and clipped at both end posts and and at each grapevine above the drip irrigation with wooden clothespins. A netting source in California is Jim's Supply .
Right before harvest, we have our enthusiastic friends and family remove the clothes pins, and roll up the netting for the next year. Please share if you use netting to protect a crop from wildlife.