Author: Joseph Morse and Richard Stouthamer

Armored scales present on California avocados are under excellent biological control and rarely build to economic levels. This study is the first to determine which species of parasitoids attack these scales and the results are somewhat different than what we expected. The dominant parasitoids in California are 5 species of unidentified and poorly studied Signiphora wasps. These account in aggregate for ca. 68% of all collected parasitoids. Fortunately, the world’s authority on signiphorid wasps, Dr. John Woolley (Texas A&M), has collaborated on this project and helped us identify these species.

Our survey for armored scales in California has so far failed to find that any of the exotic species of Mexican scales have established in California. If such a population establishes, it is difficult to know how quickly it will be detected.

A detailed study has been completed, comparing how well Aphytis melinus attacks Acutaspis albopicta (one of the major armored scales entering CA on MX avocados) in comparison to California red scale. This wasp is produced in insectaries in CA and is sold to citrus growers at a cost of ca. $0.90 per thousand wasps. Manuscripts are being prepared reporting on results of both milestones of this project.