Release, establishment and spread of the natural enemy Fopius arisanus (Hymenoptera: Braconidae) for control of the invasive oriental fruit fly Bactrocera dorsalis (Diptera: Tephritidae) in Benin, West Africa

Abstract

The opiine parasitoid Fopius arisanus is a biological control agent of frugiverous tephritid fruit flies, particularly those within the Bactrocera dorsalis complex. Over a 4-year period from 2009 to 2012, F. arisanus was released in various agro-ecological zones (Forest Savanna Mosaic [FSM], Southern Guinea Savanna [SGS], Northern Guinea Savanna [NGS] and Sudan Savanna [SS]) in Benin, in orchards of various host plants including mango, bush mango, guava, citrus and tropical almond. In the FSM zone, and specifically in bush mango plantations, we released and assessed parasitoid population phenology, establishment and spread to determine its impact on B. dorsalis populations. Two release methods were used, either as B. dorsalis parasitized pupae, or as adult parasitoids. Approximately 258,000 parasitized B. dorsalis pupae (from which 134,160 parasitoids emerged and any emerging fruit flies were trapped and not released), and 272,000 adults were released across all orchard release sites. The frequency of recoveries of F. arisanus was higher on bush mango (1-11 times) than all other fruit; the average annual percent parasitism ranged from 0.01 to 21.04. This resulted in reduction of B. dorsalis population on this crop by 33-65 % over the study period. The highest percent parasitism was about 46.53 %. In addition to the recoveries from the release sites, Fopius arisanus was consistently recovered in bush mango at 17 other locations surrounding the orchard release sites, and it continues to spread. The extent of spread was 8 km SE, 6 km W, and 8 km N of the orchard release sites in 2012. The present study is the first case study in West Africa that demonstrates the establishment, persistence and spread of F. arisanus.