What’s happening to our honey bees?
By Alicia Moulton
Honey bees are on the decline throughout the world. Here’s why.
Honey bee Colony Collapse Disorder is a complex matter with many contributing factors that have compounded over time. These factors put “an enormous burden on the immune and detoxification systems of bees, eventually ‘putting them over the edge’” (Spivak and Reuter, 2007a). Scientists have assigned the name “Colony Collapse Disorder” as a placeholder until its nature can be identified.
Factor 1 As we grow in population, we see a decrease in green, open space and an increase of buildings, roads, and other structures. This means there are fewer plants for bees to forage for food sources. Bees do best when there is a variety of pollen and nectar sources with flowers continuously blooming all season long. Farms often grow one crop type each year. This means fewer plant species and shorter periods of time when plants are in bloom.
To help bees, plant a garden with a variety of flowers, fruits, and vegetables which bloom throughout the growing season. It is also a good idea to leave unmown, herbicide-free strips of land for bees to seek refuge in if you do have to spray. Choose strips of land that do not contain noxious weeds, as the noxious weed law says weeds on the noxious weed list must be controlled. Removal of several of these weeds requires herbicides.
To help bees you can also teach your children the value of bees. Bees pollinate many of the fruits and vegetables we like to eat, and flowering plants we like to see in the landscape. They also produce honey, wax, and royal jelly. Teach them the difference between bees and wasps (See Table 1). Bees have stout, hairy bodies and are not usually aggressive towards people. Wasps have smooth bodies with a constricted waist, and are often found scavenging near garbage or picnics. Sometimes wasps can be aggressive and will sting people. Remember that while wasps are annoying if they nest around your home, some are considered predatory and beneficial insects.
Factor 2 Crop pesticides used to reduce pest insects can also kill beneficial insects like bees. Many pesticide applicators are aware of declining bee populations and use chemicals with low toxicity to bees where ever possible. However, a new class of systematic pesticides moves through plant tissue to reduce crop pests. These can add to stress on bee immune and detoxification systems because the pesticides may be present in pollen and nectar (Spivak and Reutar, 2007a), which are bees’ primary food sources.
To help bees, minimize insecticide use by only spraying when necessary. Be sure to read all pesticide labels for proper application directions. There may be several insecticides used for the same pest. Choose products least harmful to bees. Also, avoid insecticide use while plants are flowering to minimize bee kill.
Factor 3 Beekeepers are seeing depressed local honey markets. To make money, beekeepers ship bees all over the country to fill pollination contracts for almonds, blueberries, cranberries, etc. The number of acres of these crops is increasing faster than number of bees used to pollinate them, which causes pollination contract prices to increase. These crops require large numbers of honey bee colonies for pollination. For example, over 1 million bee colonies are required for California almonds in early spring. Having large numbers of bees in small areas puts nutritional stress on bees as they compete for pollen and nectar. Increased movement for pollination leads to disease transfer. “Shipping bees for pollination is like sending your kids to school,” said one beekeeper, “They come back with all the sicknesses around.”
To help bees, buy local honey. If beekeepers make more money locally, they may not need the extra money from pollination and can leave their bees home. Local honey is fresh, delicious, and it gives a warm feeling to know that you are helping local folks and getting a good product. Also, you can ask the beekeeper directly how honey is handled and if chemicals were used in production. Buying locally can create more sustainable agricultural systems.
Factor 4 Bee diseases and parasites are often present in honey bee hives. Over time, colonies can become weakened or less productive. Diseases contributing to colony collapse disorder are not new, but have been affecting bees for a while.
Varroa mites (Varroa destructor) were introduced in the U.S. in the 1980s. These mites attach to bee larvae and parasitize bees, living on the outside of the bee’s body. They are relatively large compared to the bee, about 1/6th of the bee’s body weight. To eliminate varroa mite infestations, beekeepers sometimes put insecticides (pyrethroids and organophosphates) in the beehive with the bees. Mites are becoming resistant to the insecticides and beekeepers risk residue build-up in beeswax and honey (Spivak and Reuter, 2007b).
The varroa mite is also a possible vector for several honey bee viruses, including Acute Paralysis Virus and Israeli Acute Paralysis Virus. These viruses can severely weaken bees and makes them more susceptible to other diseases (Bakonyi et al., 2002).
Acute Paralysis Virus and Israeli Acute Paralysis Virus eventually cause paralysis in honey bees. Bees are found dead outside the hive. Both viruses contribute to Colony Collapse Disorder of varroa mite-infested colonies.
Nosema apis and Nosema ceranae are internal parasites that cause nosemosis, or acute diarrhea, in bees. Honey bees are generally very clean insects and defecate outside the hive. Nosemosis causes them to be so sick they cannot make it outside to defecate. Thus, spores from fecal matter are able to infect other bees in the hive. Nosema is what causes complete disappearance of bees in the hive.
Foulbrood and chalk brood are spore-forming bacterial diseases which infect honey bee brood (Hansen and Brosgaard, 2003). Without proper sanitation, foul brood can weaken or kill a colony in one season.
Honey comb infected with Foulbrood (left) + Healthy Honey comb (right)
Nosema species, foul brood and chalk brood spores can be stored in old wax combs for years. Therefore it is important for beekeepers to remove old wax combs from hives. These can contain disease spores and pesticide residue.
Beekeepers are fighting these diseases using innovative strategies and by developing genetically resistant lines of bees. For example, some bees exhibit “hygienic behavior,” in which worker bees detect and remove 95% of diseased brood from the comb before hatching (Spivak and Reuter, 2007b). Bees which exhibit hygienic behavior detect and remove varroa mite, Nosema and Foulbrood-infected larva. Queens can pass hygienic behavior to their offspring. This means beekeepers can select for this trait and make their hives more resistant to disease!
www.extension.umn.edu/honeybees. University of Minnesota Bee Lab
Bakonyi, T., E. Grabensteiner, J. Kolodziejk, M. Rusvai, G. Topolska, W. Ritter, and N. Nowotny. 2002. Phylogenetic Analysis of Acute Bee Paralysis Virus Strains. Appl. Environ. Microbiol. 68(12):6446-6450. Available at http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=134446. Accessed May 21, 2008. University of Minnesota.
Cranshaw, W. 2008. What is a Wasp-Hornet-Yellowjacket-Bee? Available at http://www.coopext.colostate.edu/4dmg/Pests/whatis.htm. Accessed Sept. 25, 2008. Colorado State University Cooperative Extension, Entomology.
Hansen, H. and C.J. Brosgaard. 2003. Control of American foulbrood by the shaking method. APIACTA 38:140-145. Available at http://www.apimondia.org/apiacta/articles/2003/hansen_1.pdf. University of Minnesota Bee Lab.
Vetter, R. 2002. Identification Guide for California Yellowjackets. Available at http://wasps.ucr.edu/waspid.html. Accessed Sept. 25, 2008. University of California Riverside.
Spivak, M. and Reuter, R. 2007a. Why are honey bees collapsing? Available: http://www.extension.umn.edu/honeybees/components/03-26-2007_whycollapsing.html. Accessed Sept. 25, 2008. University of Minnesota Bee Lab.
Spivak, M. and G. Reuter. 2007b. A Sustainable Approach to Controlling Honey Bee Diseases and Varroa Mites. SARE Fact Sheet #03AGI2005. Available http://www.sare.org/publications/factsheet/0305.htm. Accessed May 21, 2008. University of Minnesota Bee Lab.