Larvicidal Action of Cannabidiol Oil and Neem Oil against Three Stored Product Insect Pests: Effect on Survival Time and in Progeny

SIMPLE SUMMARY: Each year, agricultural produce suffers significant loss and quality deterioration upon infestation by stored product insects. Synthetic insecticides represent a ready-to-go, effective pest control solution, albeit with several environmental and health risks. In this light and within the framework of integrated pest management research, the present study focuses on the potential insecticidal effect of two essential oils, neem oil and CBD, against 4th instar larvae of the harmful Tribolium confusum, Oryzaephilus surinamensis and Plodia interpunctella, on wheat, rice and corn seeds. CBD, especially, has been under-researched in this regard. Treatment efficacy was expressed as larval mortality in relation to dosage, time exposure intervals and product. In comparison with the control, the results showed clear dose-dependent pesticidal activity for both oils, expressed as significant larval mortality at high dose application, as high as 100% at the highest dose (90 mg/mL). Moreover, the overall survival time of the tested larvae was also considerably shorter than that of control larvae, while the treatments also produced considerably fewer offspring in the tested insects. Our results reinforce the prospect of incorporating botanical insecticides in Integrated Pest Management programs. ABSTRACT: Stored product pests can be detrimental to agricultural produce. As much as chemical pesticides are effective control agents, they involve several environmental and health risks. Within the framework of studies on alternative pest management methods, interest has focused on a plethora of plants whose extracts have demonstrated promising action as insecticides. Azadirachta indica and the derived neem oil have been extensively tested against many harmful insect species. In contrast, Cannabis sativa L. and its main compound, CBD, a highly concentrated cannabinoid, have not been investigated much. The present study examined the potential insecticidal activity of CBD and neem oils against 4th instar larvae of Tribolium confusum, Oryzaephilus surinamensis and Plodia interpunctella on wheat, rice and corn seeds. Treatment efficacy was expressed in terms of larval mortality. Mortality was observed in relation to dosage, time exposure intervals and product types. The results showed clear pesticidal activity for both oils, which at high doses induced significant mortality. The treatments produced significantly fewer offspring in the insect species tested than the control. The efficacy of treatment in progeny suppression was, as expected, dose dependent.