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Keywords:

  • essential oil;
  • fumigant toxicity;
  • nanogel;
  • persistence;
  • stored product insects

Abstract

Myristic acid–chitosan (MA-chitosan) nanogels were synthesized with the technique of self-assembly and loaded with Carum copticum (L.) essential oil. Scanning electron microscopy (SEM) study indicated nanogels with smooth surfaces and near spherical appearance, and according to transmission electron microscopy (TEM) image, core–shell stricter of nanogels was reported. Subsequently, fumigant toxicity of C. copticum oil and oil-loaded nanogels was assessed against Sitophilus granarius (L.) and Tribolium confusum Jacquelin du Val. Adults were exposed to different concentrations of the oil and oil-loaded nanogels at 27 ± 1°C and 55 ± 5% r.h. in continuous darkness. The mortality was counted after 3, 6, 10, 24 and 48 h of exposure. Mortality increased with increasing concentration levels. Fumigant toxicity of oil-loaded nanogels was significantly more than the oil even after 48 h. According to the findings, oil-loaded nanogels were 8.9- and 3.7-fold more toxic than the oil against S. granarius and T. confusum, respectively. The persistence of oil and oil-loaded nanogels was also investigated over period of time. Oil-loaded nanogels lost the insecticidal effectiveness after 21 days post-application for S. granarius and 33 days in the case of T. confusum, while the efficacy of oil decreased in the early days of application. Chemical composition of C. copticum essential oil was measured, and six components were identified. Thymol, ρ-cymene and γ-terpinolene were the major components of the oil. The essential oil-loaded nanogels may have potential to be used as an alternative to synthetic insecticides for stored products protection. However, more research is necessary to improve the findings.