Prior posts have noted the many and varied theories regarding the cause of colony collapse disorder amongst honey bees. (See also http://en.wikipedia.org/wiki/Colony_collapse_disorder.) This problems poses a risk to a huge number of agricultural products. See http://en.wikipedia.org/wiki/List_of_crop_plants_pollinated_by_bees.
I have found that as a general rule complex problems usually have complex, multi-factorial causes, which is why there is still so much debate over causation. However, there is an alternative strategy for pollination of crops, the use of wild and diverse insects.
50 researchers studied the activity of wild pollinators and managed colonies of bees on 41 different crops in 19 countries worldwide. They found that pollination by wild insects (e.g., wild bees, beetles, flies, and butterflies) resulted in a higher proportion of flowers forming seeds and fruits. Wild insects cause twice as much fruit to start to grow as equivalent visits by managed honey bees. This suggests that farmers may obtain better yields by restoring and/or conserving natural areas within fields to encourage wild pollinators rather than relying on honey bees. Such a strategy reminds of one of the practices of Integrated Pest Management ("IPM"), which similarly encouraged the conservation of natural areas so that predators would be available to attack insects causing crop damage; it also reduces the need for pesticides.
The authors of the report note that it is the great variety of shapes of wild insects mingling with flowers that spreads pollen more efficiently. Wild insects also switch more among plants and varieties, thus cross-pollinating.
Emphasizing the same theme, a separate study by European researchers showed that wild bees in general have a larger role in plant pollination than domesticated honey bees.
The study can be found at: http://www.sciencemag.org/content/339/6127/1608.short.
But all is not perfect for wild pollinators. Two recent studies have found that the number of American bumblebees is decreasing rapidly in the Midwest. Comparing an 1890 survey with current populations demonstrated that half of the wild bee species present in 1890 are present today (54 out of 109). Particularly hard hit is the American bubblebee. There are 4,000 species of wild bees in America, and 49 of them are bubblebees. After 447 hours of searching, researchers only found one American bubblebee, a queen. The American bubblebee was the most dominant bubblebee in the Midwest, but it has disappeared from much of its range. It is still strongly present in Texas and the West, however.
The studies can be found at: http://www.sciencemag.org/content/339/6127/1611 and http://www.pnas.org/content/108/2/662.short.
It is likely that the decline of insect and bee populations is the result of combination of pesticides (which weaken immune systems), disease, and parasites. There is no simple solution on the horizon, but it may be that what protects honey bees will also protect wild insect populations that contribute so much to crop pollination.