Pheromone traps put out at the end of February help determine when the male California red scales begin to fly.  Each  orchard is slightly different, depending on orientation, density of trees and location in the valley (Kern is quite a bit warmer than Madera).  We trap for scales in Tulare County, and call around for biofixes in the other counties.  Our web page shows county-wide biofixes of March 18 for Kern, March 25 for Tulare, and likely April 1 for Fresno and Madera. http://ucanr.edu/sites/KACCitrusEntomology/Home/California_Red_Scale/Degree_Days_885/

This is a great site to bookmark and follow to see when 1st and 2nd generation crawlers are emerging.  The 1st generation crawlers emerge 550 degree days after the biofix of the first male flight.  The newly settled crawlers are the easiest group of scales to control with insecticides.  For more information on monitoring and management of scales see the UC IPM guidelines http://www.ipm.ucdavis.edu/PMG/r107301111.html and the Citrograph article "The Proper Monitoring and Management of Californai Red Scale" http://www.citrusresearch.org/citromarapr2012.