Honey, which must comply with EU standard norms, must be reliable regarding food safety and sustainable colony health. High pesticide concentrations can cause high mortality in bees, loss of colonies, and honey production unsuitable for food safety. For this reason, pesticides in food have become a severe health and safety checkpoint worldwide, and demands for detecting chemicals that may pose an environmental risk have increased in recent years.
Pollination, usually performed by various bees, is an important ecosystem service for the world's flowering plants and croplands.
Honeybees, Apis mellifera L., provide pollination services to more than a hundred different crops worldwide. During blooming sessions, migratory beekeepers visit sunflower fields with more than two million pollinator colonies to get sunflower honey. The importance of sunflower honey in the global honey trade is different; its flavor is not strong dominantly. Therefore it blends well with other honey types, and it is one of the most suitable and economic honey for commercial blending. Sunflower honey is preferred to produce honey wine made from non-dominant aromatic honey, as in Spain and France.
Sunflower (Helianthus annuus), the world's fourth most used edible oil source, was produced at approximately 19.5 million tons/liter in 2020-2021, but the 2021-2022 price still increased by 50 percent. Global sunflower seed yield is affected negatively due to increased parasitic pests and decreased pollinators. Neonicotinoid pesticides have been used as an alternative to increasing oilseed yield by reducing parasite populations. Commercial beekeepers move millions of honeybee colonies to sunflower fields to get sunflower honey during the blooming sessions. The neonicotinoids contaminate the colonies via sunflower nectar and pollen during bee foraging. So, sunflower oil production related to pollinators' activity differs among countries. (Nderitu et al.;, 2008). Successful results have been obtained in analyzing multiple residues of antibiotics and pesticides in honey using liquid chromatography-mass spectrometry (LC-MS/MS). Previous studies published about the confirmation method and validation of the residues of neonicotinoids in honey are summarised below.
When sunflower and corn were planted on soils containing 2–18 µg kg-1 still imidacloprid due to previous treatments, imidacloprid was not detected in pollen and nectar (Schmuck et al. 2001).
In Austria, acetonitrile extraction and dispersive solid-phase extraction (QuEChERS type) were used in Tanner and Czerwenka's analytical method to detect neonicotinoid residues in honey. Residues of acetamiprid, thiacloprid, and thiamethoxam were detected in Austrian honey samples; however, no sample exceeded the maximum residue limits. Flower honey samples contained more neonicotinoid residues than forest honey samples (Tanner and Czerwenka 2011).
Ligor et al. developed a method using QuEChERS extraction and UHPLC/UV to determine neonicotinoid residues in honey samples. The method was applied to honey collected from Poland and other countries, including Turkey. In 19 honey samples, neonicotinoid residues were detected above the LOQ[.1] . No neonicotinoid residues were detected in the Turkish sample (Ligor et al. 2020).
Residue analyzes were carried out in honey bees sampled from sunflower grown from seeds treated with thiamethoxam or clothianidin. Residue concentrations in bee bread and adult bee samples were in the range of 0.10–2.89 ng g-1 and 0.05–0.12 ng g-1 (clothianidin); they were detected at the levels of 0.10–0.37 ng g-1 and 0.01–0.05 ng g-1 (thiamethoxam), respectively (Hernando et al. 2018).
A 3-year field study was conducted in France from 2002 to 2005 to examine pesticide residues found in colonies and honeybee (Apis mellifera L.) colony health by Chauzat et al. No pesticide residues were detected in 12.7% of the sampling periods. It was reported that no statistical relationship was found between colony mortality and pesticide residues (Chauzat et al. 2009). Imidacloprid and 6-chloronicotinic acid residues were frequently detected in pollen, honey and honeybee samples.
Mrzlikar et al. developed a reliable analytical method using two extraction techniques (SPE, QuEChERS) and LC-MS/MS (SRM) for five neonicotinoids in 51 honey samples collected between 2014 and 2016. Despite being banned in the country in 2011, residues of acetamiprid and thiacloprid were detected in low contamination (Mrzlikar et al. 2019).
An average of 8.2 ng g-1 clothianidin and 17.2 ng g-1 thiamethoxam were detected in 68% and 75% of honey samples, respectively, from hives located 30 km from Saskatchewan City in Canada. Moreover, clothianidin was found in > 50% of bee and pollen samples. Imidacloprid was detected in ~30% of honey samples (Codling et al. 2016).
The pollen, nectar, and leaves were collected to measure the residual levels of neonicotinoids using different application doses during flowering in a cotton crop especially treated with imidacloprid and thiamethoxam. Imidacloprid residues were detected between 1.61 and 64.58 ngg-1 in pollen samples and up to 1.769 ngg-1 in nectar samples. Thiamethoxam residues reached 14,521 ngg-1 in pollen samples and 4,285 ngg-1 in nectar samples. The study results provide insight into the transfer of both components to planting areas by seed treatment and the potential exposure of bees and other pollinators to systemic insecticides (Jiang et al. 2018).
A study conducted in North America from 2007 to 2008 examined the effects of pesticides on the health of bee colonies. 1% of 208 wax samples, 17.7% of 350 pollen samples and 0.0% of 140 honey samples were detected as having imidacloprid residues (Mullin et al. 2010).
Residues of neonicotinoids were investigated in honey, pollen and bee samples sampled in Greece between 2011 and 2013, while any residue did not detect in the honey samples. But 0.7–14.7 ngg clothianidin in bee samples in 2011, 6.1–69.04 ngg in pollen samples, and 2.7–39.9 ngg was detected in 2012 bee samples and 308.3–1273 ngg clothianidin in pollen samples (Kasiotis et al. 2014).
The neonicotinoid products restricted in European Union were not found in honey samples sampled in Tekirdağ on the European side of Turkey.