Toxicity and repellent activity of a carlina oxide nanoemulsion toward the South American tomato pinworm, Tuta absoluta

Abstract

Plant essential oil (EO)-based insecticides represent a promising tool for IPM, though their formulation is limited by poor physio-chemical properties. EO encapsulation into stable formulations, like nano emulsions (NEs), could boost EO e cacy and stability. Carlina acaulis roots contain an EO recently studied for its excellent insecticidal activities, and chie y composed by carlina oxide (>97%). Herein, we developed two carlina oxide NEs (0.25% and 0.5% w/w) through ultrasounds exposure and characterized them by dynamic light scattering. The NE insecticidal and repellent activities were investigated against T. absoluta eggs and larvae, and adults, respectively. 0.25% and 0.5% NEs showed a monomodal size distribution with a Z-average size of 113.87±1.32 nm and 127.27±0.47 nm, respectively. The polydispersity indexes measured at 0.15±0.01 and 0.16±0.01 indicate a low grade of polydispersity. The 0.25% NE showed signi cant contact toxicity on T. absoluta eggs, with a maximum egg hatching inhibition of 85.7% 11 days post-treatment. The highest larvicidal effect was observed in translaminar toxicity tests, with complete mortality after 24 h. The NE did not achieve signi cant oviposition deterrence. Overall, the tested NE showed promising effectiveness as ovicide and larvicide on T. absoluta, highlighting the need of further research shedding light on its modes of action, as well as to evaluate lethal and sublethal effects on tomato biological control agents and pollinators. Key MessageNanoemulsion (NE) can boost the stability and the e cacy of insecticidal essential oils.Here we developed carlina oxide NEs for insecticidal applications against Tuta absoluta. 0.25% (w/w) carlina oxide NE was stable for 3 months and slightly phytotoxic to tomato.The NE was toxic towards T. absoluta eggs and larvae.No oviposition deterrence effects were detected on adults.