Essential oils from plant resources as potent insecticides and repellents: Current status and future perspectives

The extensive use of chemical pesticides on crop plants is harmful to mankind as well as to insect predators. Their long-term usage contaminates water, soil, and the food chain with the accumulation of toxic residues. Plant-based essential oils with a broad spectrum of antifungal, larvicidal, ovicidal, and pesticidal activities are now being preferred as an alternative and sustainable source to safeguard crop plants. Evidence now exists that essential oils alter the nervous and locomotor activities of insects. They target specific and may affect the various systems of the insect pests. This may generally do no or less harm to mammals including humans when compared to chemical insect pests, therefore they can be deployed as relatively safer molecules to reign in the devastating pests and reduce economic losses. They are cost-effective, available throughout the year, non-persistent in the environment, and vertebrate or non-target toxicity is minimal in comparison with chemical pesticides. This brief review focuses on the current status of essential oils used as potent pesticides, stored-product insect pest reduction, insect repellents, and fungicides. This also suggests the way forward to design superior strategies such as the technique of nano-encapsulation to ameliorate the stability and stave off their volatilization.