Abstract:
The tomato leafminer, Tuta absoluta is a destructive invasive pest of cultivated
tomato and other Solanaceae plants, with yield losses of 80-100%. Mirid
predators are key natural enemies of T. absoluta, but they also feed on host
plants in the absence of their prey. Management of T. absoluta is a challenge due
to its high biotic potential, resistance to many insecticides and the absence of
sufficiently adapted auxiliary fauna in its new dispersion zones. Olfaction plays an
important role in the tritrophic interaction between tomato, its herbivore pest T.
absoluta and its mirid predators, which can be influenced by non-host plant
odors. However, how non-host odours shape this interaction is poorly
understood. Previously, we had demonstrated belowground crop protection
properties of certain Asteraceae plants against the root-knot nematode
Meloidogyne incognita, pest of tomato and other Solanaceae plants.
Additionally, Asteraceae plants impact negatively on feeding behavior of
above-ground pests of Solanaceae plants, including the greenhouse whitefly
(Trialeurodes vaporariorum) and green peach aphid (Myzus persicae). Here, we
tested the hypothesis that foliar volatiles from some of these non-host
Asteraceae plants can influence the tomato-T. absoluta-mirid predator
tritrophic interaction. In olfactometer assays, T. absoluta females were
attracted to volatiles of the Solanaceae host plants tomato and giant
nightshade but avoided volatiles of the Asteraceae plants, blackjack and
marigold, and the positive control, wild tomato, when tested alone or in
combination with the host plants. Coupled gas chromatography-mass
spectrometry analysis showed that host and non-host plants varied in their
emission of volatiles, mainly monoterpenes and sesquiterpenes. Random forest
analysis combined with behavioral assays identified monoterpenes as the host
plant attractive blend to T. absoluta and its mirid predator, with sesquiterpenes
identified as the non-host plant repellent blend against T. absoluta. Contrastingly,
the mirid predator was indifferent to the non-host plant repellent sesquiterpenes. Our findings indicate that terpenes influence the tomato-T. absoluta-mirid
predator tritrophic interaction. Further, our results emphasize the importance
of studying crop protection from a holistic approach to identify companion crops
that serve multi-functional roles.
