It is variously reported that honey bees pollinate between 100-130 crops that span the entire cultivated crop spectrum- fruits and vegetables, nuts, herbs and spices, livestock forage, and oil crops. That is everything from apples and avocados to turnips and watermelon, almonds to macadamia nuts, allspice to oregano, alfalfa to sweet clover, canola to sunflower. The extent of pollination dictates the maximum number of fruits a tree or plant will bear and honey bees are responsible for more than 80% of the pollination in cultivated crops.
The honey bee, an immigrant from Europe, is an essential element to our monoculture form of agriculture. It is not really suprising since most of our crops and many of our garden plants evolved in areas where honey bees were native, and both crops and insects were brought to the United States with the colonists to become essential parts of our agricultural system. With modern agriculture’s vast fields and groves of a single kind of plant all flowering at the same time, farmers can’t depend on feral honey bees that happen to nest near crop fields. The single flowering will not support a large bee population. Instead, farmers contract with migratory beekeepers, who move millions of bee hives to fields each year just as crops flower. To pollinate California’s estimated 420,000 acres of almond trees alone takes more than 1 million honey bee colonies that are trucked to the groves in trucks.
In the 1990s two species of parasitic mites were accidentally introduced from Asia. The tracheal mite and varroa mite caused severe declines in honey bee populations within a few years. These parasitic mites were finally controlled in honey bee hives by using with chemical pesticides, substantially increasing the costs of large beekeeping operations. Until then many beekeepers had avoided pesticides. Unfortunately, the feral populations of honey bees that once thrived in the wild and brought genetic diversity to the honey bee population were essentially killed off by the parasitic mites, and no longer contribute substantial genetic variability to the managed bee populations.
Then during the winter of 2006-2007, a large number of bee colonies died out, losses were reported to be between 30% to 90% in the impacted beekeeping operations. While many of the colonies lost during this time period exhibited the symptoms from parasitic mites, many were lost, from unknown cause. The next winter, the number of impacted honey bee operations spread across the country. Honey bee colonies died out at even higher rates. The phenomenon was termed Colony Collapse Disorder, or CCD. No disease or cause was identified, the adult honey bees seemed to just disappear with very few dead bees found near the impacted colonies. The impacted colonies had low levels of parasitic mites and minimal evidence of wax moth or small hive beetle damage. The other active bee colonies did not steel the food reserves, they avoided the impacted hives. Often there was still a laying queen and a small cluster of newly emerged attendants present.
There appears to be no end in sight, CCD is spreading around the world. This mysterious disappearance of honey bees is troubling, the bee population is falling and we may end up with insufficient numbers of pollinators to fulfill the demands of our agricultural industry. Last winter, 31% of the U.S. honey bee colonies were wiped out. The year before that it was reported as 21% of colonies lost. These losses if they continue could have a catastrophic impact on agriculture, and we do not know what is causing the problem let alone how to fix it. One third of all food eaten in the United States requires honey bee pollination.
Current theories about the cause(s) of CCD include increased losses due to the invasive varroa mite; new or emerging diseases, especially mortality by a new Nosema species related to the microporidian giardia; and pesticide poisoning (through exposure to pesticides applied for crop pest control or for in-hive insect or mite control). Neonicotinoids, a relatively new class of chemical insecticides, are highly toxic to bees, and can cause behavioral changes to bees at sub-lethal doses. These chemicals could be a potential factor in CCD. In response to the crisis, the European Commission (EC) announced this past spring that it intends to impose a two-year ban on the entire class of pesticides known as Neonicotinoids
In addition to these suspects, the U.S. Department of Agriculture believes the a likely cause of CCD is a potential immune-suppressing stress on bees, caused by one or a combination of several factors. Stresses may include poor nutrition, drought, and migratory stress brought about by the increased need to move bees long distances to provide pollination services to farmers. It is believed that by confining bees during transport, or increasing contact among colonies in different hives, the industry has increased the transmission of pathogens and spread CCD. Some researchers suspect that stress could be compromising the immune system of bees, making colonies more susceptible to disease.
CCD may not be an entirely new and distinct phenomenon. Large-scale honey bee die-offs and disappearances have reportedly happened in the past. Historic literature describes spring dwindle disease, fall dwindle, or autumn collapse in bee keeping. In 1975, honey bees experienced Disappearing Disease which affected a large number of bee colonies in the U.S. It may never be determined if these historic situations share a common cause with the current crisis, but unfortunately with the loss of feral populations to the Asian mite and cheap sources of imported honey the honey bee keeping industry was at a low point when CCD began to strike.