Vehrs, S.L.C., & Grafton-Cardwell, E.E. 1994 Chlorpyrifos effect on armored scale (Homoptera: Diaspididae) populations in San Joaquin Valley citrus.. Journal of Economic Entomology 87(4): 1046-1057.

Notes: Abstract: Portions of three citrus orchards infested with California red scale, Aonidiella aurantii and yellow scale (A. citrina) were sprayed either with a commercial rate of chlorpyrifos or left unsprayed; the three orchards included a chlorpyrifos-susceptible A. aurantii population, chlorpyrifos-resistant A. aurantii population, and a chlorpyrifos-resistant A. citrina population.