Abstract
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.
Highlights
Bees are essential for plant propagation[1], but factors such as pathogens, habitat losses and intensive pesticide use are reducing their populations[2]
Bees are exposed to insecticides during the pollen and nectar harvesting through contact with the treated plant surface and the ingestion of sap from seeds coated with systemic insecticides[5,6] abamectin, acetamiprid, cartap-hydrochloride, chlorfenapyr, deltamethrin and thiamethoxam were toxic to Apis mellifera Linnaeus, 1758 (Hymenoptera: Apidae) workers by direct spraying; diet treated and contact with pulverized leaves[2]
Oregano and thyme oils were mainly toxic to A. mellifera and should be used with caution in pest control
Summary
Bees are essential for plant propagation[1], but factors such as pathogens, habitat losses and intensive pesticide use are reducing their populations[2]. Larvae mortality was high and adult mobility of Melipona quadrifasciata Lepeletier, 1836 (Hymenoptera: Apidae) low with diet treated with imidacloprid[7]. These insecticides act on arthropods, causing physiological and behavioral effects by directly interfering in the acetylcholine receptors[7]. The vulnerability of A. mellifera to pesticides has been studied[2,10] but the effect of these products on native stingless bees such as Trigona hyalinata (Lepeletier) (Hymenoptera: Apidae) is little understood. Leaf Leaf Leaf/Flower threat, besides being native and important in agrosystems[11] Behavioral mechanisms, such as escape after the detection of irritants or repellents, may reduce the contact of insects with toxic substances[7,12]. Plant substances may repel or are toxic to bees and natural enemies[19,20,21] and require toxicological evaluation
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