Sublethal effects of plant essential oils toward the zoophytophagous mirid Nesidiocoris tenuis

Zoophytophagous hemipteran predators provide relevant biological control services and their applications are consolidated in greenhouse pest management. The use of plant essential oils (EOs) for sustainable crop protection is being currently promoted. However, further knowledge of the potential side effects of EOs on predatory mirids (Hemiptera: Miridae) is required. Here, we evaluated the non-target impact of four EOs (anise, fennel, garlic and lavender) on the generalist predator Nesidiocoris tenuis (Reuter) in the laboratory. The baseline toxicity of EOs was firstly assessed on N. tenuis adults following topical contact exposure. Then, the predator reproduction and orientation behavior was tested following the exposure to three estimated EO lethal concentrations (LC1, LC10 and LC30). Garlic EO had the lowest estimated LCs (e.g., LC30 1.34 mg mL−1), being thus the most toxic compound among the tested EOs. The estimated LC30s for lavender, anise and fennel EOs were 2.75, 4.55 and 5.17 mg mL−1, respectively. The fertility and the orientation behavior of N. tenuis females was negatively affected by all the EOs at the highest tested concentration. Nevertheless, anise EO at LC1 and LC10 caused no sublethal effects on N. tenuis. Our findings suggest that careful attention should be given when EOs are used in combination with N. tenuis in pest management programs.