1. Res., Dept. of Agroenvironmental Sci. and Technol., Univ. of Bologna, v. Filippo Re, 6, 40126 Bologna, Italy. E-mail: fventura@agrsci. unibo.it
2. Farm Advisor, Univ. of California Cooperative Extension, Ventura County, Ventura, CA 92250. E-mail: bafaber@ucdavis.edu
3. Farm Advisor, Univ. of California Cooperative Extension, Imperial County, 1050 E. Holton Rd., Holtville, CA. E-mail: kmbali@ucdavis.edu
4. Extension Biometeorologist, Univ. of California, One Shields Ave., Dept. of Land, Air, and Water Resour., Davis, CA 95616. E-mail: rlsnyder @ucdavis.edu
5. Full Prof., Dipartimento di Economia e Sistemi Arborei, Univ. of Sassari, V. E. De Nicola 1, 07100 Sassari, Italy. E-mail: spano@ssmain. uniss.it