Selectivity of the botanical compounds to the pollinators Apis mellifera and Trigona hyalinata (Hymenoptera: Apidae).

The toxicity of essential oils that can be used in insect pest management to pollinators needs further studies. Apis mellifera Linnaeus and Trigona hyalinata (Lepeletier) (Hymenoptera: Apidae) foragers were exposed by three pathways to ginger, mint, oregano and thyme essential oils to provide their LC50, LD50 and LC90, LD90. Oregano and thyme were more toxic through contact and topically for A. mellifera while the toxicity of mint and ginger was lower. Trigona hyalinata was more tolerant to the essential oils than A. mellifera. In the walking test, the area was treated (totally or partially) with sub-doses (LC50) obtained via contact. The area fully treated with oregano reduced the distance traveled and the movement speed increased the number of stops by A. mellifera. Similar results were observed for T. hyalinata with oregano and thyme oils. Apis mellifera showed irritability remaining shorter time in the area partially treated with ginger, mint and thyme essential oils while T. hyalinata had similar behavior with ginger and thyme. Essential oils did not repel A. mellifera or T. hyalinata, but those of ginger, mint and thyme reduced the time spent by A. mellifera in areas treated with sublethal doses. Oregano and thyme essential oils reduced the survival, mainly, of A. mellifera, while ginger and mint were selective for both pollinators.

Bioactivity of the Cymbopogon citratus (Poaceae) essential oil and its terpenoid constituents on the predatory bug, Podisus nigrispinus (Heteroptera: Pentatomidae).

Podisus nigrispinus Dallas (Heteroptera: Pentatomidae), released in biological control programs, is a predator of Lepidopteran and Coleopteran species. Lemongrass essential oil and its constituents can be toxic to this natural enemy. The major constituents of lemongrass essential oil are neral (31.5%), citral (26.1%), and geranyl acetate (2.27%). Six concentrations of lemongrass essential oil and of its citral and geranyl acetate constituents were applied to the thorax of P. nigrispinus nymphs and adults. The walking and respiratory behavior of the P. nigrispinus third-instar nymphs, treated with citral and geranyl acetate at the LD50 and LD90 doses, were analyzed with video and respirometer. The lemongrass essential oil toxicity increased from first- to fifth-instar P. nigrispinus nymphs. The P. nigrispinus respiration rates (µL de CO2 h-1/insect) with citral and geranyl acetate in the LD50 and LD90 differed. Nymphs exposed to the lemongrass essential oil and its constituents on treated surfaces presented irritability or were repelled. Podisus nigrispinus adults were tolerant to the lemongrass essential oil and its constituents, geranyl acetate and citral. The altered respiratory activity with geranyl acetate and the fact that they were irritated and repelled by citral suggest caution with regard to the use of the lemongrass essential oil and its constituents in integrated pest management incorporating this predator, in order to avoid diminishing its efficiency against the pests.