Potential source of ecofriendly insecticides: Essential oil induces avoidance and cause lower impairment on the activity of a stingless bee than organosynthetic insecticides, in laboratory.

The negative effect of insecticides on bees has been reported as one of the factors associated with the decline in population of these pollinators. Thus, the aim of this study was to evaluate the response of the stingless bee Nannotrigona aff. testaceicornis (Lepeletier, 1836) to a promising source of new insecticide molecules obtained from Lippia sidoides (rosemary pepper) essential oil (EO) and its major compounds (thymol, ρ-cymene, and (E)-caryophyllene), comparing them to commercial insecticides (organosynthetic: imidacloprid, deltamethrin and semisynthetic: spinetoram). For this, stingless bees were exposed by contact with these compounds to evaluate the lethal and sublethal (locomotion and flight orientation) toxicity. The L. sidoides EO and its major compounds have low lethal toxicity to forager worker bees (N. aff. testaceicornis). The organosynthetics imidacloprid (LD50 =0.00146 µgbee-1) and deltamethrin (LD50 =0.0096 µg bee-1) were about 209,589 and 31,875 times more toxic, respectively, than the least toxic natural compound, (E)-caryophyllene (LD50 =306 µgbee-1). Locomotion ability and flight orientation were little affected by spinetoram and by L. sidoides EO and its major compounds, however, were greatly reduced by the imidacloprid and deltamethrin insecticides. Besides shows low lethal and sublethal toxicity, the bioinsecticides were also avoided by the forager bees. Individuals treated with the L. sidoides EO and thymol were avoided by the untreated bees. Therefore, the natural products studied here were promising due to their recognized effectiveness against pest insects and greater safety to bees N. aff. testaceicornis.

Sub-lethal effects of essential oil of Lippia sidoides on drywood termite Cryptotermes brevis (Blattodea: Termitoidea).

The drywood termite Cryptotermes brevis (Walker, 1853) (Kalotermitidae) is one of the most important wood structural pest in the world. Substances from the secondary metabolism of plants (e.g., essential oils) have been considered an environmentally safer form of control for urban pests, such as termites. In the present study, we analyzed the lethal and sub-lethal effects of essential oil of Lippia sidoides and its major components on C. brevis pseudergates in two routes of exposure (contact and fumigation). The essential oil of L. sidoides and thymol were more toxic to C. brevis pseudergates when applied by contact (LD50 = 9.33 and 8.20µgmg-1, respectively) and by fumigation (LC50 = 9.10 and 23.6µLL-1, respectively). In general, treatments changed the individual and collective behaviors of C. brevis pseudergates, as well as the displacement and walking speed. The essential oil of L. sidoides and its major components showed a high potential to control C. brevis pseudergates, due to the bioactivity in the two routes of exposure and the sub-lethal effects on the behavior and walking, important activities for the cohesion of C. brevis colonies.