The stingless bee Trigona spinipes (Hymenoptera: Apidae) is at risk from a range of insecticides via direct ingestion and trophallactic exchanges

BACKGROUND

The stingless bee, Trigona spinipes, is an important pollinator of numerous native and cultivated plants. Trigona spinipes populations can be negatively impacted by insecticides commonly used for pest control in crops. However, this species has been neglected in toxicological studies. Here we observed the effects of seven insecticides on the survival of bees that had fed directly on insecticide-contaminated food sources or received insecticides via trophallactic exchanges between nestmates. The effects of insecticides on flight behavior were also determined for the compounds considered to be of low toxicity.

RESULTS

Imidacloprid, spinosad and malathion were categorized as highly toxic to T. spinipes, whereas lambda-cyhalothrin, methomyl and chlorfenapyr were of medium to low toxicity and interfered with two aspects of flight behavior evaluated here. Chlorantraniliprole was the only insecticide tested here that had no significant effect on T. spinipes survival, although it did interfere with one aspect of flight capacity. A single bee that had ingested malathion, spinosad or imidacloprid, could contaminate three, four and nineteen other bees, respectively via trophallaxis, resulting in the death of the recipients.

CONCLUSION

This is the first study to evaluate the ecotoxicology of a range of insecticides that not only negatively affected T. spinipes survival, but also interfered with flight capacity, a very important aspect of pollination behavior. The toxicity of the insecticides was observed following direct ingestion and also via trophallactic exchanges between nestmates, highlighting the possibility of lethal effects of these insecticides spreading throughout the colony, reducing the survival of non-foraging individuals. © 2023 Society of Chemical Industry.

Lethal and sublethal effects of insecticides used in the management of Plutella xylostella (Lepidoptera: Plutellidae) on the predator Cycloneda sanguinea L. (Coleoptera: Coccinellidae)

BACKGROUND

The application of synthetic insecticides is the main strategy used to reduce the damage caused by the diamondback moth Plutella xylostella in commercial Brassica crops. However, incorrect insecticide use can cause biological and ecological disturbances in agroecosystems. Cycloneda sanguinea is a generalist voracious predator and is distributed widely in cultivated and noncultivated ecosystems. This study investigated the efficiency of four insecticides for the control of P. xylostella and the lethal and sublethal effects of these insecticides on C. sanguinea.

RESULTS

Spinosad (92% mortality) and chlorfenapyr (76% mortality) were highly toxic to P. xylostela. However, chlorantraniliprole (10% mortality) and methomyl (no mortality) were ineffective against this pest. Chlorantraniliprole was the only insecticide that was highly toxic to C. sanguinea by contact (90% mortality), however, it was nontoxic following the ingestion of chlorantraniliprole-contaminated aphids. Interestingly, ingestion of prey contaminated with methomyl and chlorfenapyr was highly toxic (100% mortality) to C. sanguinea. Spinosad was nontoxic to C. sanguinea via exposure to contaminated surfaces and following ingestion of contaminated prey. However, direct contact of the insects with both methomyl and spinosad significantly affected C. sanguinea flight activity (vertical flight and free-fall flight), whereas chlorfenapyr impacted vertical flight only.

CONCLUSION

These findings showed that chlorantraniliprole was not only ineffective for the control of P. xylostela, but was also highly toxic to C. sanguinea. The results indicated that spinosad was efficient against P. xylostela and was of low toxicity to C. sanguinea; however, the deleterious effects of this insecticide on flight behavior could result in reduced predatory efficiency. © 2022 Society of Chemical Industry.