Direct and Indirect Effects of Ivermectin on Phytophagous, Frugivorous and Parasitoid Insects

Ivermectin, an anthelmintic used in livestock, is excreted in faeces and can therefore affect non-target organisms. While its effects on coprophagous insects have been well studied, recent research suggests that it can be taken up by plants, raising the possibility that it may affect a much wider range of invertebrates than previously known. Our study investigated the effects of ivermectin on insects from different feeding guilds. First, we tested its effects on the larvae of the noctuid moths <i>Spodoptera frugiperda</i> and <i>Helicoverpa armigera</i> (chewing herbivores) using an artificial diet. Secondly, we investigated the effects of its presence in the soil of pea plants <i>Pisum sativum</i> on the pea-feeding aphid <i>Acyrthosiphon pisum</i> (phloem-feeding herbivore). Thirdly, we tested ivermectin in an artificial diet for <i>Drosophila melanogaster</i> used as a host for the parasitoid <i>Pachycrepoideus vindemmiae</i>. Our results showed that ivermectin reduced pupal weight and survival in moth larvae, inhibited aphid colony establishment and reduced parasitoid emergence rates from ivermectin-exposed <i>Drosophila</i> pupae. These results highlight the potential of ivermectin to affect multiple trophic levels and emphasise the need for sustainable veterinary practices in the use of anthelmintics in free-ranging livestock and companion animals.