A Worrying Trend in Bee Populations

BY ANNELIESE MOLL
For the UAS Whalesong
Bees are an extremely important species that are a necessary component of the reproduction of many flowering plant species. In 2013 there were around 2 million bees in the United States, but that number is steadily declining. This decline should be a huge wake up call since domesticated bees and their wild counterparts are vital to our agricultural system and contribute billions of dollars to the United States crop production. World wide, bees pollinate one-third of the world’s crops.
There are several reasons potentially behind their decline. Honeybees are being attacked on several fronts: colony collapse disorder and mites are two large problems.
Colony collapse disorder is a condition in honeybee colonies that was first described in 2006 (Engelsdorp 2014). It is an unexplained condition where bees suddenly disappear. Within beekeeping there is an acceptable amount of loss that can be expected due to natural hardships, this is around 15% of a colony. Unfortunately, within the last few years reported losses have been consistently greater. There is also not much that can be done in regards to colony collapse disorder. This is mainly due to the fact that colony collapse is not caused by one factor.
The mites, Varroa destructor, were originally confined to a region east of the Urals and into Afghanistan. However, due to a lack of attention to this parasite has now spread across the world.
The life cycle of the Varroa destructor is fairly simple. There are two stages: a phoretic stage and a reproductive stage. Phoretic simply means an inter-species biological interaction, in this case it’s a parasitic relationship, and the phoront is the mite. During the mite’s phoretic stage they ride around on the adult bees and consume their blood, which leaves them weaker and more prone to infections because of the open wounds. This stage usually lasts around 5-11 days depending on whether there is brood in the hive. Where there isn’t a brood the mites maybe forced to remain in this stage for up to 6 months.
In their second stage, the female mites lay their eggs in only the capped brood cells. Since the brood cells are capped, the mites have special appendages, peretrimers, which act as a snorkel allowing the mites to breath. While in the cell the mites also spin small cocoons where they will develop into prepupa. Typically, the mite does not feed until five hours after the cocoon has been completed and the first mite eggs are laid around 70 hours later. The number of mite eggs differs slightly depending on the roll of bee, the number usually between 5 or 6 eggs. Sadly, hives that have been infested by these mites typically die within two or three years.
According to the International Bee Research Association, there are more than 25,000 species of bees in world. Most of these bees are defenseless against these mites, but there are a few species that are not.
There are 5 bee labs sponsored by the USDA. In one such lab there is an experimental breeding program focused on mite resistant bees. In this program researchers are breeding bees that are resistant to these mites. However, these bees are starting to lose traits such as gentleness and their ability to store honey. This has resulted in those researchers working closely with commercial beekeepers (USDA-ARS Bee Labs).

References:
Engelsdorp, D. V., Pettis, J. S., & Ritter, W. (2014). Colony collapse disorder. Bee health and veterinarians, 157-159.
“USDA-ARS Bee Labs – EXtension.” USDA-ARS Bee Labs – EXtension. EXtension, 29 May 2015. Web. 19 Oct. 2015.
Rosenkranz, P., Aumeier, P., & Ziegelmann, B. (2010). Biology and control of Varroa destructor. Journal of invertebrate pathology, 103, S96-S119.
Tepedino, V. J. (1979). The importance of bees and other insect pollinators in maintaining floral species composition. Great Basin naturalist memoirs, 139-150.

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