Classical biological control of the pink hibiscus mealybug, Maconellicoccus hirsutus (Green), in southern California

A cooperative classical biological control project against the pink hibiscus mealybug, Maconellicoccus hirsutus (Green), infestation in the low-desert region of California was initiated in the fall of 1999. Subsequently, the parasitoids Anagyrus kamali Moursi (Encyrtidae), Gyranusoidea indica Shafee, Alam & Agarwal (Encyrtidae) and Allotropa sp. nr. mecrida (Walker) (Platygastridae) were reared and released for permanent establishment. Population densities of mealybug and percent parasitism were monitored at a number of mulberry tree and carob tree sites for five consecutive years. The population density of M. hirsutus within the first year was reduced by approximately 95%. Over the entire 5-year period of the project, the average regional population density of the mealybug exhibited a continued decline. Anagyrus kamali was the predominant parasitoid, often parasitizing in excess of 50% of the mid-to-late stage M. hirsutus in the first 2 years following the parasitoid’s release. Although Gyranusoidea indica was rarely found from spring through early fall, it did represent 40% of the parasitoid species composition during winter. By 2005, the platygastrid parasitoid, Allotropa sp. nr. mecrida did not appear to be established following numerous releases in 2003 and 2004. Hyperparasitism of A. kamali by resident species (Marietta sp. & Chartocerus sp.) was frequently over 35% during 2000. However, hyperparasitism was considerably lower during each successive year, coincident with declining densities of both mealybug and the primary parasitoid host. Field collections of two other species of mealybugs common in Imperial Valley demonstrated that they are not being utilized as alternate non-target hosts by the newly introduced parasitoids.