Tomato plant defence activation by Nesidiocoris tenuis and persistence of its effects against Tuta absoluta

Nesidiocoris tenuis (Reuter) (Hemiptera Miridae) is an omnivorous predator widely used in the control of tomato pests. This zoophytophagous mirid is capable of inducing plant defences in tomato due to its phytophagous behaviour with significant adverse effects on mites and whiteflies. However, the effects of plant defence induced by N. tenuis on Tuta absoluta (Meyrick) (Lepidoptera Gelechiidae) have not been searched in detail. In this study, the density threshold of N. tenuis nymphs per plant for induction of defence on T. absoluta was searched by placing 3, 6 or 10 nymphs on each of the top and bottom leaf of young tomato plants for 4 days. The results showed that oviposition by T. absoluta females was significantly reduced on the plants punctured by the highest predator density in comparison to control plants. Further experiments showed that plants punctuated with the highest predator density were more repellent to T. absoluta for either period of 7 or 14 days after the removal of predators, compared to control plants. The systemic nature of the induced defences was also confirmed in all periods post treatment. The results offer valuable information in critical aspects of plant defence effects induced by N. tenuis on T. absoluta such as the number of predators required per plant, their systemic nature and the persistence of the effects induced.