Exploitation of new attractants for fruit fly pests of economic importance

Abstract

The fruit fly tribe Dacini (Tephritidae: Diptera) comprises more than 700 species including many fruit pests of economic importance, particularly in the two genera, Bactrocera and Zeugodacus. Males of many dacine species show strong affinity either to methyl eugenol (ME) or cue-lure (CL). However, there are over a hundred species that show no affinity to these lures. We have been seeking new attractants for these ‘nonresponding’ species particularly of endemic agricultural importance based on the following three criteria, (1) by observing their mating sequences, (2) their natural interactions with plants and (3) by analyzing specific chemicals the wild male flies accumulate in their secretory organ (rectal gland) associated with pheromone production. Orchid flowers of many Bulbophyllum species attract fruit fly males by emitting specific volatiles for pollination, in the rain forests of Southeast Asia. Several species produce either ME or raspberry ketone (RK), and some species use zingerone (ZN) to attract both ME-sensitive and RK-sensitive males. ZN was found as a specific male attractant for B. jarvisi. A specific attractant for the solanaceous fruit fly, B. latifrons, was characterized as 3-hydroxy-α-ionone from a specific variety of eggplants. Several 3-oxygenated α-ionone analogs were developed as monitoring agents for B. latifrons in Okinawa, Japan. Furthermore, wild Bactrocera males that have fed on attractants from certain plant sources selectively accumulate/biotransform compounds in the rectal gland possibly for sex pheromone to attract females. A sesquiterpene, β-caryophyllene, was identified from the rectal gland in wild B. correcta males. β-Caryophyllene was found to be more attractive than ME to males, and thus, potentially serves as a new monitoring agent for B. correcta. These exemplify the importance of a multidisciplinary study including behavioral, physiological, biochemical and chemoecological aspects to develop new fruit fly attractants.