Toxicity of Cinnamomum spp. essential oil to Tuta absoluta and to predatory mirid

The South American tomato pinworm Tuta absoluta (Meyrick, 1971) (Lepidoptera: Gelechiidae) causes economic losses in solanaceous crops. Chemical pesticides are the main management methods used against this pest, which causes the emergence of resistances in pest populations. Therefore, it is crucial to identify and develop new molecules showing toxicity to T. absoluta while being less harmful to the environment, to beneficial organisms and to human health. The objective of this study was to evaluate the lethal and sublethal effects of three essential oils (EOs) of Cinnamomum spp. (Lauraceae) against T. absoluta. We evaluated the effects of the EOs during the life cycle of the pest using an age-stage, two-sex life table. We assessed leaf consumption by T. absoluta treated with EOs or the main compounds found in EOs, cinnamaldehyde and linalool. Additionally, we investigated the toxicity of the EOs to the predator Macrolophus basicornis (Stal, 1860) (Hemiptera: Miridae). Our findings indicate that EOs significantly decreased the duration of all life cycle stages of T. absoluta in 5 days, as well as fecundity by 55%, oviposition period by 2 days and viability of second generation eggs by 50%. Cinnamaldehyde and linalool resulted in 83.3% and 86.7% mortality, respectively, of T. absoluta larvae, showing that these major EO compound significantly contribute to EO insecticidal activity. However, all three EOs caused between 43 and 53% of mortality to M. basicornis. Although Cinnamomum essential oils show great insecticidal potential for T. absoluta, they may not be compatible with other IPM tools such as the use of biocontrol agents when used at the LD50 for T. absoluta.

Automated summary

This study evaluated the lethal and sublethal effects of Cinnamomum essential oils on Tuta absoluta and found that the essential oils significantly decreased the duration of the pest's life cycle stages and fecundity, as well as showed high toxicity to the larvae. However, the essential oils also caused significant mortality to the predatory insect Macrolophus basicornis, indicating potential incompatibilities with other integrated pest management tools.