Mortality of the oriental fruit fly, Bactrocera dorsalis, during pupation in insect pest suppressive soils

The oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), is an important pest of various crops. Little is known about the role naturally present soil‐entomopathogens play in its mortality. Preimaginal mortality of B. dorsalis during pupation in soil was determined in 3‐dl plastic pots in the laboratory, simulating natural conditions. Eleven treatments included standard potting soil, sterilized sand, no pupation medium, standard soil amended one‐by‐one with beneficial soil organisms [the fungi Beauveria bassiana (Bals.‐Criv.) Vuill., Metarhizium robertsii JF Bisch, SA Rehner & Humber, Isaria fumosorosea Wize, and Glomus spp. (each one dose), and the nematode Steinernema feltiae (Filipjev) (three doses)], and standard soil amended with a consortium of beneficals. Preimaginal mortality varied widely from 32–36% (Glomus spp., untreated soil, and S. feltiae low dose) to 85% (no pupation medium). From all treatments with beneficials, amending standard potting soil with a high dose of S. feltiae caused the highest mortality (80%). A microbial consortium led to much higher mortality (77.5%) than any of its single components alone: S. feltiae medium dose (58%), B. bassiana (56%), and M. robertsii (50%). The two other microbial treatments (I. fumosorosea and Glomus spp.) did not significantly increase mortality compared to untreated soil during pupation. We conclude that mortality during pupation of B. dorsalis under field conditions is likely to be highly important to the population dynamics of the pest. Therefore, management of the soil in agricultural fields, including orchards, to favour microbial antagonists of insects can be a powerful tool in the management of this important pest.