Disappearing Bees: An Update on Research
We all know how important bees are to us as eaters. There are 20,000 species of bees worldwide, 700 in the Northeastern United States alone. But one species, the honey bee, has been managed, bred and studied like no other. In Pennsylvania, honey bee pollination services contribute $53 million to the economy.
Given the importance of bees and pollination, the current loss of bees is a critical concern. In 2006 the complex of problems causing adult bees to leave the hive was named Colony Collapse Disorder (CCD). We have lost about one-third of hives every year for the past five years to this devastating problem. But honey bees are not alone. The National Academy of Science declared in 2006 that “overall pollinators are in decline.”
What is causing this decline in honey bee populations? Dr. Frazier named the top suspects:
Varoa mites feed on the blood of bees and vector viruses. The insecticide used to treat the mites is also harmful to the bees.
IAPV virus is a new virus. It is difficult to show that disease is the cause of colony collapse disorder. But statistics show that hives that have died more often had diseases. These hives had many viruses present. Eighty percent had IAPV in one study.
Nosema is a parasitic fungus. Found in Taiwan for the first time in 2005, it is now in Western bee populations.
Pesticides. This aspect has been the focus of the research at Penn State because they have both a Toxicologist and a Physiologist. There are many ways that bees can come in contact with pesticides. Remember honey bees travel over 3.7 miles from the hive on a regular basis, covering 27,932 acres. If they are under stress, they can double that distance. Given this wide foraging radius, even bee hives on organic land are likely to come in contact with pesticides in their travels.
In order to figure out which pesticides might be affecting bees, Penn State researchers did a screen of 171 pesticides. They found 121 different pesticides and metabolites (887 samples). One of the most worrying aspects of what they found is that on average, each pollen sample had 6.7 different pesticides (up to 31). Even though it is required for individual pesticides to be tested and labeled for their impact on bees, the effect of complexes of pesticides is not tested or known.
Researchers also studied the inert ingredients in pesticides. The active ingredient is the regulated portion of a pesticide; inerts are relatively unregulated. There are three big classes of inerts. One of them is organosilocans. All four organosilocans “caused the bees to have impaired learning,” Dr. Frazier told us. This is important since one of the mysterious things about colony collapse is that adult bees don’t return to the hive. This may in part be caused by impaired learning.
Poor nutrition and stress may also contribute to bee population decline. Herbicide use reduces the amount of healthy forage for bees. Without enough food, populations are stressed.
All of these factors are working together against the bees. “Nutrition, mites, pesticides and stress are interfering with the bee immune system,” is the conclusion so far. Maryann Frazier and others will continue to investigate.