Polymer-based encapsulation of peppermint oil () nanoemulsion and its effects on life and some physiological activities of honeybees (Hymenoptera

Background
Nanotechnology is thought to be a promising way to create more reliable and effective products in many fields, that is, biological pest-control methods. Biopesticides based on plant extracts, for example, essential oils, are often a complementary or alternative treatment option. The honeybee is expected to be exposed for many applied pesticides. In this work, preparation and characterization of peppermint oil nanoformulation was carried out. The effects of prepared formulation were studied on adult workers of honeybee by oral and contact methods, in addition to evaluating some physiological parameters.
Objective
Honeybees are beneficial and economically important insects and have a major role in crop production because they are considered insect pollinators, representing 80% of insect pollinators, in addition to economic bee products such as honey, pollen, royal jelly, wax, propolis, and venom. Therefore, it is sensitive and is greatly affected by environmental changes, especially the pesticides used on those crops. Recently, nanoproducts appeared in fertilizers and pesticides and used them without knowing their effect on other living organisms in the surrounding environment, the most important of which are beneficial insects such as worker honeybees. The aim of the research was whether nanoparticles had a harmful effect on bees in terms of death rate and enzymatic activity.
Materials and methods
Four different concentrations of menthol extract and nanomenthol extract (1250, 2500, 3750, and 5000 ppm) were studied on the life of adult workers of honeybee by oral and contact methods (LC and LC). In addition, the effect of these treatments on physiological effects through chemical analysis was done to determine amylase enzyme, protein, and lipid contents.
Results and conclusion
Encapsulation of peppermint oil nanoemulsion using sodium alginate by cross-linking with calcium chloride was done successfully. Transmission electron microscopy images showed that nanocapsules exhibited a nearly spherical shape. Gas chromatography/mass spectrometry indicated no change in oil constituents after the loading process. Encapsulation efficiency and loaded-capacity percentages were evaluated. Mortality percentages for workers treated with peppermint nanoemulsion and crude emulsion were calculated and compared with control. The highest mortality occurred in nanoemulsion than crude oil, and increased at 5000 ppm for both treatments. LC value of nanoemulsion in oral treatment was 2629.85 ppm, but in contact treatment was 4246.84 ppm. While LC value of crude extract in oral treatment was 5471.13 ppm and in contact treatment was 11 895.65 ppm. Estimated amylase, total protein, and lipid contents in adult honeybees were significantly affected by different treatments. Nanopreparations are more toxic on honeybee workers than their crude materials. Both preparations (nano and bulk materials) have biochemical and physiological effects on honeybee works when exposed to them either by oral or contact treatments.