Abstract
Simple SummaryThe maize weevil (Sitophilus zeamais Motsch) is a major pest in stored grain, responsible for significant economic losses and having a negative impact on food security. Due to the harmful effects of traditional chemical controls, it has become necessary to find new insecticides that are both effective and safe. In this sense, plant-derived products such as essential oils (EOs) appear to be appropriate alternatives. Therefore, laboratory assays were carried out to determine the chemical compositions, as well as the bioactivities, of various EOs extracted from aromatic plants on the maize weevil. The results showed that the tested EOs were toxic by contact and/or fumigance, and many of them had a strong repellent effect. Samples of 14 EOs and 17 of their main constituents (monoterpenes) had high fumigant toxicity against S. zeamais adults and might constitute a viable control method of this pest.Chemical control of the maize weevil (Sitophilus zeamais) has been ineffective and presents serious collateral damage. Among plant-derived insecticides, essential oils (EOs) are suitable candidates to control this stored products pest. In this work, the insecticidal activities of 45 natural EOs against S. zeamais adults were screened, and the most promising ones (24 EOs) were characterized by GC–MS. The repellent and toxic effects (contact and fumigant) of these 24 EOs were determined, and by a cluster analysis they were classified into two groups considering its fumigant activity and contact toxicity. For the EOs with the highest fumigant potential (14 oils) and their main active constituents (17 compounds), lethal concentrations were determined. The most active EOs were those obtained from L. stoechas and L. alba, with LC50 values of 303.4 and 254.1 µL/L air and characterized by a high content of monoterpenes. Regarding the major compounds, the oxygenated monoterpenes R-(+)-pulegone (LC50 = 0.580 mg/L air), S-(-)-pulegone (LC50 = 0.971 mg/L air) and R-(-)-carvone (LC50 = 1.423 mg/L air) were the most active, as few variations in their concentrations significantly increased insect mortality.
Highlights
Cereal production is essential to guaranteeing food security because cereals constitute between 50–60% of the human diet and are an excellent source of macro and micronutrients [1]
The essential oils (EOs) that exhibited the highest mortality rates (>90%) were those extracted from R. officinalis, L. stoechas, S. viminea, M. septentrionalis, Eucalyptus sp., and L
Potential toxic contact activity on S. zeamais has been reported for the essential oil of L. alba, an effect attributed to its high limonene content [32]
Summary
Cereal production is essential to guaranteeing food security because cereals constitute between 50–60% of the human diet and are an excellent source of macro and micronutrients [1] An advantage of these products is their possibility for being stored for long periods of time without losing their nutritional value; they are available all throughout the year [2]. In storing grain in bulk in warehouses or silos it is difficult to prevent and control insect infestations [10] In this sense, insecticides with fumigant action are the most effective method for controlling pests in stored products, because due to their high volatility they can spread throughout the air space of the silo and reach areas that would not otherwise be accessible [12]. Commercial pesticides are usually not very selective, and many are toxic to the environment and harmful to health [13,14]
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