Among botanical extracts used as insecticides, essential oils (EOs) are promising alternatives to chemical insecticides. EOs are synthesized by plants, and they play a key role in plant signaling processes including also attractiveness toward pollinators and beneficial insects. Plant species producing essential oils (over 17,000 species) are called aromatic plants and are distributed worldwide. Our review aims to evaluate research studies published in the last 15 years concerning the use of EOs in stored product protection. More than 50% of the retrieved manuscripts have been published by authors from Eastern countries (Iran, China, India, and Pakistan), investigating different aspects related to insect pest management (exposure route, effect on the target pest, and mode of action). Coleoptera was the most studied insect order (85.41%) followed by Lepidoptera (11.49%), whereas few studies targeted new emerging pests (e.g., Psocoptera). Almost all the trials were carried out under laboratory conditions, while no experiments were conducted under real operating conditions. Future research studies concerning the use of EOs as insecticides should focus on the development of insecticide formulations which could be successfully applied to different production realities.

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The repeated use of conventional synthetic pesticides in crop protection leads to resistance development by pests along with a negative impact on the environment, particularly non-target arthropods. Plant-derived active compounds, such as essential oils (EOs), play a key role in sustainably controlling pests. The lethal and sublethal activity of citrus peel EOs as emulsions and included in polyethylene glycol (PEG) nanoparticles (EO-NPs) was determined against the invasive tomato pest Tuta absoluta. Their effects on the plants were also assessed. The results showed an overall good insecticidal activity of the compounds tested, with a higher mortality through contact on eggs and larvae by EO emulsions and through ingestion on larvae by EO-NPs. The nanoformulation also significantly reduced the visible toxic effects on the plants. The data collected suggest that these natural compounds, especially when nanoformulated, could be successfully used in integrated pest management programs for T. absoluta.

We studied the acute toxicity and the sublethal effects, on reproduction and host-killing activity, of four widely used insecticides on the generalist parasitoid Bracon nigricans (Hymenoptera: Braconidae), a natural enemy of the invasive tomato pest, Tuta absoluta (Lepidoptera: Gelechiidae). Laboratory bioassays were conducted applying maximum insecticide label rates at three constant temperatures, 25, 35 and 40°C, considered as regular, high and very high, respectively. Data on female survival and offspring production were used to calculate population growth indexes as a measure of population recovery after pesticide exposure. Spinetoram caused 80% mortality at 25°C and 100% at higher temperatures, while spinosad caused 100% mortality under all temperature regimes. Cyantraniliprole was slightly toxic to B. nigricans adults in terms of acute toxicity at the three temperatures, while it did not cause any sublethal effects in egg-laying and host-killing activities. The interaction between the two tested factors (insecticide and temperature) significantly influenced the number of eggs laid by the parasitoid, which was the lowest in the case of females exposed to chlorantraniliprole at 35°C. Furthermore, significantly lower B. nigricans demographic growth indexes were estimated for all the insecticides under all temperature conditions, with the exception of chlorantraniliprole at 25°C. Our findings highlight an interaction between high temperatures and insecticide exposure, which suggests a need for including natural stressors, such as temperature, in pesticide risk assessments procedures.

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Synthetic chemicals are extensively used to limit the substantial crop damage induced by two closely related scale insects, the vine mealybug Planococcus ficus (Signoret) and the citrus mealybug Planococcus citri Risso (Hemiptera: Pseudococcidae). Both organisms are economically important pests occurring in vineyards and/or in citrus orchards worldwide. Synthetic chemicals can be either incorporated in pesticides aimed at directly controlling these pests or used as semiochemicals (i.e., sex pheromones) for monitoring, mass trapping, mating disruption, and/or for kairomonal attraction to enhance parasitoid performances. Growing evidence of both an alarming bee decline and destruction of auxiliary fauna driven by pesticides have stimulated an urgent need for in-depth research clarifying the adverse side effects of pesticides on beneficial arthropods. We have reviewed the current knowledge on mealybug pest control based on insecticides and semiochemicals. We highlight the following major advances: (1) How the active substances of insecticides (four organophosphates, imidacloprid, buprofezin, and spirotetramat) affect target and non-target organisms, (2) in which contexts and how a semiochemical-based strategy could be applied to deal with serious mealybug infestations, and (3) the implications of the appropriate exploitation of these synthetic chemicals for sustainable development. Using selective insecticides with novel modes of action and long-lasting efficacy in combination with eco-friendly semiochemical-based tools is a promising strategy for developing sustainable integrated pest management programs. This would help to maintain biodiversity dynamics and vital ecosystem services, thereby sustaining crop yields.

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