The competitive population interactions between Aphytis maculicornis and Coccophagoides utilis were analyzed in order to determine their roles in controlling olive scale, Parlatoria oleae, in California olive groves. There is strong evidence that the two parasites working together give better control of olive scale than does A. maculicornis working alone. Conclusions are based on observations of parasite populations at selected groves over a period of five years.

K-values for various factors affecting olive scale mortality were developed in order to measure and assess the controlling effects of these two parasites on olive scale from generation to generation.