Herbivore-induced plant volatiles allow detection of Trichoplusia ni (Lepidoptera: Noctuidae) infestation on greenhouse tomato plants

Monitoring of insect populations is an important component of integrated pest management and typically is based on the presence and number of insects in various development stages. Yet, plants respond to insect herbivory and release herbivore induced plant volatiles (HIPVs) which could be exploited in monitoring systems. Our objective was to investigate whether the information associated with HIPVs has potential to become part of advanced technologies for monitoring pest insect populations. In a laboratory experiment, we determined that tomato plants, Lycopersicon esculentum Mill cv. Clarence, each infested with 20 caterpillars of the cabbage looper, Trichoplusia ni (Hübner), emit HIIPVs of which we selected (Z)-3-hexenyl acetate, (E)- β-ocimene and β-caryophyllene as chemicals indicative of herbivory. Using an ultra-fast portable gas chromatograph (zNose) in a research greenhouse and in a commercial greenhouse, we could (i) reveal differential emissions of these three indicator chemicals from plants with or without herbivory, (ii) detect herbivory within 6 h of its onset, (iii) track changes in indicator chemical emissions over time, and (iv) study the effect of environmental and crop maintenance related factors on the emission of indicator chemicals. HIPVs appear promising as reliable indicators of plants health but further studies are needed to fully understand the potential of this concept.