MA-chitosan nanogel loaded with Cuminum cyminum essential oil for efficient management of two stored product beetle pests

Abstract

Natural essential oils have received increased attention as alternatives to synthetic pesticides for pest management of foodstuffs. Recently, microencapsulation and other controlled release techniques are used to increase insecticidal efficiency and persistence of essential oils with slow and controlled release. In this study, the possibility of improving the insecticidal activity of plant essential oils was investigated for effective management of two stored product beetle pests. Self-assembly technique was used to prepare nanogels of myristic acid-chitosan loaded by essential oil extracted from cumin, Cuminum cyminum L. Fumigant toxicity of C. cyminum oil and oil-loaded nanogels (OLNs) were investigated at 4, 7, 10, 13, and 16 µL/L air against the granary weevil Sitophilus granarius L. and 8, 11, 14, 17, and 20 µL/L air for confused flour beetle Tribolium confusum Jacquelin du Val. Experiments were conducted at 27 ± 1 °C and 55 ± 5 % relative humidity in continuous darkness. Insecticidal bioassay revealed that OLNs were more toxic than C. cyminum oil against tested beetle pests. The persistence of the oil and OLNs was also evaluated against two tested species. Results indicated that C. cyminum oil completely lost its insecticidal activity after 12 days, whereas at the same period, the OLNs lost about 60 % of its activity when applied against S. granarius and 15% for T. confusum. Therefore, it could be concluded that encapsulation improved the persistence of the oil.