David Owens, Extension Entomologist, owensd@udel.edu
Between April 14 and 21, we captured our first San Jose Scale in an apple orchard near Bridgeville using pheromone traps but have not captured any since. Typically, male scales emerge around petal fall, and crawlers are active in June. Where we have our traps, the apples have not yet reached the petal fall stage. During the growing season, the crawler stage is the best time to hit scales if you are going to use an insecticide, based on scouting and recent history or blemishes on last year’s fruit. You can scout for crawlers starting around 300 degree days (base 51 °F) after male emergence by using a piece of black electrical tape wrapped around a limb with the sticky side up. Around 380 degree days, crawlers should begin to appear, and around 600 – 700 degree days crawlers will be at their peak. University of Kentucky has a good San Jose Scale fact sheet with the information above: https://entomology.ca.uky.edu/ef204. If we intercept more scales in our traps, I will post that information here.