**1. Introduction**

The European or western honey bee, *Apis mellifera* L., is relied upon extensively worldwide for pollinating approximately 75% of crop species in agricultural and horticultural cropping systems at a value of \$15–\$17 billion per year in the USA and \$170–\$200 billion per year globally [1–3]. When foraging for pollen and nectar in flowering plants, honey bees can be exposed to a diverse array of pesticides, including: insecticides, fungicides, and herbicides [4–8] that can cause direct or indirect toxic effects to honey bees [9]. Direct toxicity occurs when honey bees are immediately killed when exposed to wet sprays or dried pesticide residues on leaves or flowers [10, 11]. Indirect toxicity is associated with sublethal effects on foraging behavior, development, orientation, reproduction, learning and memory retention, immune system functionality, longevity, and overwintering survival. Indirect

effects may also be related to social interactions resulting from sharing a contaminated food source [11–13]. However, any direct or indirect effects depend on the age of honey bees, because larvae or brood tend to be more susceptible to pesticides than adults [14].

Insecticides are known to be directly or indirectly harmful to honey bees [15–18] with recent research focusing primarily on the direct or indirect effects of neonicotinoid insecticides (imidacloprid, thiamethoxam, dinotefuran, clothianidin, acetamiprid, and thiacloprid) on honey bees, which has resulted in some neonicotinoids, such as: imidacloprid, thiamethoxam, and clothianidin being banned in the European Union and other countries [19–26]. However, although the initial focus has been on insecticides, research demonstrates that other pesticides and compounds can have direct or indirect effects on honey bees, such as; fungicides, insect growth regulators, herbicides, and adjuvants. Therefore, this chapter discusses the issues regarding the effects of fungicides, insect growth regulators, herbicides, and adjuvants on honey bee health.
