Grafton-Cardwell, E.E., Ouyang, Y., Striggow, R.A., & Vehrs, S.L.C. 2001 Armored scale insecticide resistance challenges San Joaquin Valley citrus growers.. California Agriculture 55(5): 20-25.

Notes: Organophosphate and carbamate insecticides have been used to treat citrus pest problems for more than 40 years. From 1990 to 1998, we documented California red scale [Aonidiella aurantii] and yellow scale [A. citrina] resistance to these insecticides. Armoured scale resistance is found on an estimated 40% of 163000 acres of citrus in the San Joaquin Valley. Citrus growers have responded by either increasing their use of natural enemies, especially the parasitoid wasp Aphytis melinus, or by applying newly registered insect growth regulator or neonicotinoid insecticides. While the California red scale problem is, for the moment, greatly reduced, outbreaks reduced, outbreaks of cottony cushion scale are occurring because the new insecticides are highly toxic to the predatory vedalia beetle.