**4. Herbicides**

Herbicides are the most widely used pesticides in agricultural and horticultural cropping systems for control of unwanted vegetation or plant material [27, 35, 72]. Therefore, herbicides should have minimal, if any, direct or indirect effects on honey bees [34, 73, 74]. The post-emergent herbicides, dicamba and picloram, were found not to be directly harmful to adult honey bees or brood [73, 74]. However, the contact, post-emergent herbicide, paraquat, was reported to be directly harmful to honey bees [75]. In addition, laboratory studies found that honey bee colonies

**5**

**6. Conclusion**

*Effects of Pesticides and Adjuvants on the Honey Bee,* Apis mellifera*: An Updated Bibliographic…*

fed two herbicides, 2,4-D and 2,4-trichlorophenoxyacetis acid, resulted in negative effects on brood development, but there were no toxic effects to adult honey bees

Furthermore, the herbicide, glyphosate (sold as Roundup®), which is a broadspectrum, post-emergent herbicide [76], and is the most widely used pesticide worldwide [77–79], exhibits no direct harmful effects to honey bees [80]. However, research has shown that glyphosate may exhibit indirect effects on honey bees by influencing foraging behavior [79], navigation [81], or beneficial gut microbiota [82]. Nevertheless, it is important to differentiate the effects of laboratory and field studies to assess how glyphosate actually directly or indirectly affects honey bees. There are a host of factors that can influence the direct and indirect effects of herbicides on honey bees including: herbicide used application rate, method and timing of application, and location that honey bees are foraging for pollen, nectar,

Herbicides, in general, are more likely to have indirect effects on honey bees by eliminating plants (weeds) that, when in flower, provide pollen and nectar for honey bees during foraging [18, 33, 84]. Consequently, any reduction in floral resource availability (pollen and nectar) could indirectly affect honey bee development, foraging, and survival of managed honey bees [85]. In addition, this could lead to starvation, resulting in a reduction in colony health and winter survival [13].

Honey bees are exposed to a multitude of pesticides while foraging for pollen and nectar in flowering plants, and many formulated pesticides that are applied to control insect and mite pests, or diseases typically contain adjuvants [5, 7, 8]. Therefore, honey bees are likely being directly exposed to adjuvants when foraging [7]. Adjuvants are compounds that are a component of the pesticide formulation (as an "inert ingredient") or are added as a tank-mix additive [86, 87]. Adjuvants are designed to enhance the effectiveness of pesticides, including insecticides and herbicides, by improving or altering deposition, increasing toxicity, improving

Some of the most widely used adjuvants are surfactants that increase pesticide efficacy by reducing the surface tension of spray droplets, which allows the spray solution to cover more leaf surface area—especially waxy or hairy leaf surfaces of certain plants [5, 7, 88]. In addition, surfactants have been shown to have insecticidal and miticidal properties [89–92]. Initially, surfactants were assumed to be biologically inert with no direct or indirect harmful effects to honey bees [7, 93]. However, studies show that certain surfactants may be toxic to honey bees [88, 94, 95], especially the organosilicone surfactants, which are reported to exhibit direct and indirect harmful effects to honey bees [5, 7, 94, 96]. Nonetheless, the mechanism by which organosilicone surfactants indirectly affect honey bees, such as,

The European or western honey bee, *Apis mellifera*, is exposed to a diverse array of pesticides when foraging on flowering plants for pollen and nectar. Although insecticides are commonly encountered, honey bees are also exposed to other pesticides (fungicides, insect growth regulators, and herbicides) and compounds (adjuvants) that can result in direct or indirect effects on individual honey bees,

mixing ability, and/or extending residual activity or persistence [86].

impairing learning ability, is not known [5].

*DOI: http://dx.doi.org/10.5772/intechopen.89082*

[33, 73, 74].

and water [83].

**5. Adjuvants**

*Effects of Pesticides and Adjuvants on the Honey Bee,* Apis mellifera*: An Updated Bibliographic… DOI: http://dx.doi.org/10.5772/intechopen.89082*

fed two herbicides, 2,4-D and 2,4-trichlorophenoxyacetis acid, resulted in negative effects on brood development, but there were no toxic effects to adult honey bees [33, 73, 74].

Furthermore, the herbicide, glyphosate (sold as Roundup®), which is a broadspectrum, post-emergent herbicide [76], and is the most widely used pesticide worldwide [77–79], exhibits no direct harmful effects to honey bees [80]. However, research has shown that glyphosate may exhibit indirect effects on honey bees by influencing foraging behavior [79], navigation [81], or beneficial gut microbiota [82]. Nevertheless, it is important to differentiate the effects of laboratory and field studies to assess how glyphosate actually directly or indirectly affects honey bees. There are a host of factors that can influence the direct and indirect effects of herbicides on honey bees including: herbicide used application rate, method and timing of application, and location that honey bees are foraging for pollen, nectar, and water [83].

Herbicides, in general, are more likely to have indirect effects on honey bees by eliminating plants (weeds) that, when in flower, provide pollen and nectar for honey bees during foraging [18, 33, 84]. Consequently, any reduction in floral resource availability (pollen and nectar) could indirectly affect honey bee development, foraging, and survival of managed honey bees [85]. In addition, this could lead to starvation, resulting in a reduction in colony health and winter survival [13].
