**1. Introduction**

Honey bees contribute more than 90% of the global pollination of more than approximately 85% of the total cross-pollinated plant species in the world, the blessing of being able to hover around and pollinate this much diverse array of floral plant species comes with a curse to these bees, of being in unremitting contact with a wide array of stresses like, parasites, predators, diseases, chemical, etc. present in the environment [1–3]. As being the most successful and commercially exploited pollinators in agro-ecosystems not just for their pollination duties but for commercially valuable by-products such as, honey, wax, propolis, etc. as well, honey bees faces more diverse stresses in nature. Honeybees (*Apis mellifera*) are exposed to an ever changing array of xenobiotics from both natural and synthetic sources. Thousands of older foraging worker honey bees travel as far as 10 km from the hive in the course of collecting the nectar, pollen, water, and propolis needed to sustain a colony of tens of thousands of young adult workers, immature bees, and male reproductive or drones [4]. While foraging over this large area for collecting pollen and nectar to satisfy the carbohydrate needs of the colony, bees forage in various flowering plants with different nature, but these food sources are not always entirely pure every time, having either different plant derived chemicals or the widely used toxic agro-chemicals mixed with them. With the ever increasing use of synthetic chemical pesticides in agriculture honey bees and other wild pollinators have faced a serious threat to their global biodiversity in recent decades [5–7]. Nectar and pollen may contain environmental pollutants or

systemic pesticides drawn from the soil, or they can be contaminated from topical pesticide applications or drift from such applications. Different agro-chemicals like, herbicides, fungicides and most importantly the insecticides, alone and in combination with other factors such as elevated temperature, production of hybrid varieties with lesser quantity of pollen and nectar in their flowers, have caused a devastating effect on honey bees at a global level [2, 8, 9]. Bee foragers may bring such contaminated floral rewards back to the colony for feeding and storing as a resource for future generations [10]. Pesticides which are being used in agriculture crops are highly toxic to bees as they kill the bees through many ways such as, direct killing of foraging workers with their acute toxicity, drifting out from agricultural land to nearby apiaries, thus, making the whole colony more susceptible to different pathogens and to some point reduce their possibility to thrive in the nature by getting accumulated in the pollen inside the colony. Nectars produced by some flowering plant species also contain plant-synthesized chemicals which are toxic to different pollinators [11].

The introduction of chemical pesticides and further increase in its demand in the market is not actually the basic requirements of the farmer; rather it is their mere ignorance. The farmers discriminately use these agro-chemicals with a purpose to manage the pests; instead, they end up with killing their own beneficial insects, i.e., the pollinators. Honey bees and other pollinators get exposed to different toxic agro-chemicals in nature through different paths and these different pesticides affect honey bee colonies to different levels thus; to minimize the losses to pollinators from the adverse effect of pesticide poisoning is a burning topic of interest for human to protect the pollinators.
