Abstract:
Bactrocera dorsalis (Hendel) is a major pest of fruits and vegetables
worldwide with documented losses of up to 100%. Various management
techniques including the use of parasitoids, such as Fopius arisanus (Sonan)
and Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae)
within the context of the Integrated Pest Management (IPM) approach
have been deployed for its control. The effectiveness of parasitoids is
well understood, but knowledge of the semiochemicals that mediate their
behavior, as well as that of the host fruit fly to tree-attached mangoes, is
lacking. Here, we first compared the attractiveness of the above-mentioned
fruit fly and its parasitoids to volatiles of different treatments (non-infested
physiologically mature unripe and ripe mangoes, mangoes newly exposed to
ovipositing B. dorsalis, and mangoes on day 7 and day 9 post-oviposition)
of tree-attached Kent, Apple, and Haden mango varieties relative to control
(clean air). The fruit fly was significantly more attracted to the mango volatiles
(up to 93% of responsive insects) compared to the control (clean air).
Fopius arisanus was significantly more attracted to mangoes with ovipositing
fruit flies (68–76%) while D. longicaudata was significantly more attracted
to day 9 post-oviposited mangoes (64–72%) compared to the control.
Secondly, we elucidated the headspace volatile profiles of the non-infested
and infested tree-attached mangoes using gas chromatography linked to
mass spectrometry (GC-MS). The volatiles revealed various types of organic
compounds with qualitative and quantitative differences. The majority of
the compounds were esters making 33.8% of the total number, followed by sesquiterpenes-16.4%, and monoterpenes-15.4% among others. Most
compounds had higher release rates in headspace volatiles of fruit fly-infested
mangoes. Lastly, we harvested the infested mangoes and incubated them for
puparia recovery. The number of puparia recovered varied according to the
mango variety with Apple mango registering 81.7% of the total, while none was
recovered from Kent. These results represent the first report of the changes
in the headspace components of non-infested and infested tree-attached
mangoes and the associated differential responses of the mentioned insects.
A follow-up study can reveal whether there is a convergence in olfactomes
which is significant when developing baits that selectively attract the fruit fly
and not its natural enemies and fill the knowledge gap from an evolutionary
ecological perspective.
