Essential oils from Varronia curassavica (Cordiaceae) accessions and their compounds (E)-caryophyllene and α-humulene as an alternative to control Dorymyrmex thoracius (Formicidae: Dolichoderinae).

The process of urbanization of natural environments has dramatically increased the incidence of pest insects. To control these organisms in urban environments, the last decades have been marked by an increase in the use of synthetic insecticides. However, the intensive and indiscriminate use of synthetic insecticides has provoked a series of environmental problems and human health. In this way, the concern and the searching for environmentally safer alternatives for the control of urban pests is increasing. In the present study we evaluated the lethal and sublethal effects of essential oils (EOs) of six accessions of Varronia curassavica (Jacq.) (Cordiaceae) and their constituents (E)-caryophyllene and α-humulene on the ant Dorymyrmex thoracicus Gallardo, 1916 (Formicidae: Dolichoderinae), a species commonly found in urban environments and which can cause damage to human health. Bioassays of fumigation toxicity and locomotor activity in partially treated arenas were performed. The lethal concentrations to kill 50% of the D. thoracicus population ranged from 0.69 to 2.48 µL/L for EOs and from 3.75 to 1.49 µL/L for the (E)-caryophyllene and α-humulene compounds. The survival of the ants exposed to LC95 of the treatments was reduced over time, ranging from 4.2 to 35.6 h to kill 50% of the D. thoracicus population. In general, EOs of V. curassavica caused repellency and affected the locomotor activity of the ants. Our results indicate that EOs of V. curassavica are a promising source for the control of the urban ant D. thoracicus.

Apis mellifera (Insecta: Hymenoptera) in the target of neonicotinoids: A one-way ticket? Bioinsecticides can be an alternative.

The recent decline of Apis mellifera populations around the world has been subject of intense research due to ecological and economic damages resulting from the loss of pollination services. The intensive use of insecticides from the neonicotinoids group is among the possible causal factors of this decline, including also sub-lethal effects. However, the use of synthetic insecticides has been increased on a global scale in the recent decades. In order to evaluate an alternative to the use of neonicotinoids, this work investigated the effects of a bioinsecticide and its major compound on A. mellifera (Apidae: Hymenoptera), one of the main pollinators of crop plants. For this, bees were exposed, by contact and ingestion, to the essential oil of Cymbopogon martinii (Poaceae: Poales), to geraniol (major compound) and the insecticide imidacloprid to evaluate the toxicity and behavioral effects as well as the locomotion changes and immune responses of bees treated with these compounds. In general, toxicity was greater through ingestion and the insecticide imidacloprid was more toxic to A. mellifera compared to the essential oil and its major compound. The individual and collective behaviors (i.e. trophallaxis, grooming, avoidance) as well as the immune responses of bees were not significantly affected by bioinsecticides. However, the locomotion response and flight orientation of the bees were significantly altered by insecticide when administered by ingestion. Our results highlight the potential of C. martinii essential oil and its major compound as a possible alternative to mitigate the harmful effects of neonicotinoids on bees.