Non-target effects of essential oil-based biopesticides for crop protection: Impact on natural enemies, pollinators, and soil invertebrates

The control of arthropod pests of agricultural importance is increasingly difficult due to the quick development of resistance in the targeted pest populations coupled to their massive non-target lethal and sublethal effects. This fostered the progressive banning of active ingredients at international and national levels, making pest management challenging. Reliable and environmentally sustainable pest control tools are required. Botanicals, with special reference to plant essential oils (EOs), can represent a broad source of active ingredients to develop effective insecticides and acaricides for agricultural purposes. In this context, our review analyzed the literature currently available about the lethal and sublethal activity of EOs on non-target terrestrial invertebrates in agricultural settings, including biological control agents (predators and parasitoids), pollinators and soil nontarget species. Even if EO-based insecticides and acaricides are generally considered safer from a non-target point of view, a number of detrimental effects have been noted on biological control agents, including negative effects on respiration rate, reduced predatory ability and reduced parasitization rates, among others. Examples of sublethal effects experienced by pollinators exposed to EO-based pesticides are the reduction in the movement speed and distance travelled, while the toxicity of EO-based products on soil invertebrates is limited. Of note, the modes of action leading to EO toxicity on non-target species are scarcely studied. Further research on long-term non-target effects of EO-based pesticides in the field is still needed.