Pesticides as a cause of honeybee (Apis mellifera) mortality and their persistence in honey

Abstract

Recently, there has been a widespread decline in honeybee (Apis mellifera) colonies globally, disrupting ecological balance and reducing the pollination capacity of many entomophilous plants. One of the primary causes of bee family deaths is the increasing use of pesticides, particularly insecticides, in agricultural practice. This study aimed to identify the causes of bee family mortality in various regions of Ukraine during 2021–2022 and to determine the breakdown potential of different pesticide groups in honey. Pesticide residues in biological samples were analyzed using liquid chromatography-mass spectrometry (UPLC-MS/MS) and gas chromatography-mass spectrometry (GC-MS/MS). In the bodies of dead bees, residues of various pesticides from different chemical groups, as well as their mixtures, were detected. In most cases, the cause of bee poisoning was mixtures of pyrethroids and neonicotinoids: thiamethoxam, clothianidin, and lambda-cyhalothrin; imidacloprid, lambda-cyhalothrin, and thiamethoxam; as well as clothianidin and lambda-cyhalothrin. The primary pesticides found in honey were neonicotinoids (58.8%), triazoles (29.6%), strobilurins (6.5%), and benzimidazoles (5.1%). Most pesticide levels did not exceed the maximum allowable levels in honey. The neonicotinoids detected in honey included thiacloprid, acetamiprid, imidacloprid, clothianidin, and thiamethoxam. The triazoles detected included tebuconazole, cyproconazole, flutriafol, and epoxiconazole; strobilurins included picoxystrobin, pyraclostrobin, and azoxystrobin; and benzimidazoles included carbendazim and thiophanate-methyl. Residues of neonicotinoids, triazoles, benzimidazoles, and strobilurins in honey did not undergo degradation over 12 months of storage at 4 °C. Storing honey at 20 °C after 12 months increased the degradation of thiacloprid by 21.2%, acetamiprid by 20.7%, and flutriafol by 36.3%. Between the 9th and 12th months at 20 °C, picoxystrobin concentration decreased by 24.5–38.0%, and carbendazim concentration decreased by 80.0% to a complete breakdown of residues in honey. The degradation of thiophanate-methyl in honey at 20 °C reached 28.0% by the 6th month, 46.0% by the 9th month, and 55.4% by the 12th month. This persistence of most pesticides in honey poses a significant risk of toxic effects on bee families as well as on human health