Tuta absoluta-induced plant volatiles: attractiveness towards the generalist predator Macrolophus pygmaeus

Abstract

One of the most damaging insect pests to tomato crops is the tomato leafminer, Tuta absoluta. Current control methods are not efficient at regulating this pest below the economic threshold, leading to the development of new strategies based on its natural enemies. In this study, we evaluated the ability of Macrolophus pygmaeus to discriminate T. absoluta-infested plants versus non-infested tomato plants. We subsequently collected volatile organic chemicals released by tomato plants under different levels of infestation, and identified the associated herbivore-induced plant volatiles (HIPVs). Behavioural assays were conducted in a double-choice olfactometer and flight tunnel. In both systems, M. pygmaeus was significantly attracted towards infested plants. Because distance attraction is likely to be mediated, at least partially, by volatile organic compounds, HIPVs were collected from healthy and infested plants using a dynamic volatile collection system. Volatile chemical profiles vary with the level of infestation; specifically, twice as many chemicals were identified under infestation by 20 T. absoluta larvae compared to healthy plants. A total of 35 compounds were identified, with β-phellandrene, 2-carene, β-caryophyllene, α-pinene and α-phellandrene representing 76–86 % of the total blend. The release of monoterpenes was strongly influenced by the level of caterpillar infestation, while the amount of sesquiterpenes did not vary significantly. We hypothesise that certain HIPVs, most likely monoterpenes, are involved in prey location by M. pygmaeus and have potential to manipulate the natural enemies of T. absoluta to enhance the control of this crop pest.