The decline in one of our primary pollinators has been of great concern in recent years. In the UK alone bees are considered to provide £400 million per annum to the economy through pollination of commercial fruit and veg crops. Not to mention their tasty vomit (honey)! Recent research in the USA points to lethal amounts of pesticides and fungicides entering the bee colony through pollen (bees use pollen as a source of fats and proteins). Interestingly there appears to be some connection to the plants the bees were supposed to be pollinating (hives are moved to track the different growing seasons). When bees were pollinating either blueberry, cranberry, cucumber, pumpkin or watermelon, they chose to feed on pollen from weeds and wildflowers. These plants are typically the targets of pesticides and thus the bees natural foraging abilities, combined with aggressive agricultural practices maybe contributing to lethal doses of toxins in bee colonies that themselves make the bees less resistant to gut parasites.
Recent declines in honey bee populations and increasing demand for insect-pollinated crops raise concerns about pollinator shortages. Pesticide exposure and pathogens may interact to have strong negative effects on managed honey bee colonies. Such findings are of great concern given the large numbers and high levels of pesticides found in honey bee colonies.
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0070182#abstract0