Hi all
I was recently chided for "paraphrasing" Marla Spivak's talk at WAS in October. Here is an excerpt of her own words, printed in the WAS Journal, quoted for review purposes only:


One recent study (among many!) helps illustrate the benefit of good floral nutrition for bees. This study was conducted by Matthew Smart, a recent PhD in my lab. He asked the question: How do agricultural landscapes affect the health and survivorship of honey bee colonies? He collaborated with a commercial beekeeper in North Dakota and studied colonies distributed among six apiaries over three years. The colonies were transported to California for almond pollination every winter and were returned to North Dakota for honey production each summer. 

Each of the summer apiaries was surrounded mostly by corn and soybean fields, but also had varying degrees of uncultivated land along roadsides, ditches, and wetlands (quantified by USGS). Mites and diseases were controlled effectively by the beekeeper, and residue analysis of pesticides in bee pollen did not reveal an effect of pesticide exposure on colony survivorship. 

The most significant predictors of colony health and survivorship each year were related to nutrition. The apiary surrounded by the most floral forage had an average of 12% loss of colonies each year, while the apiary surrounded by the least forage had over 40% loss each year. The only difference between these apiaries was the availability of flowers. 

An important component of the above study was that the beekeeper effectively controlled Varroa mite levels in all colonies. If mites were not controlled, many more colonies would have succumbed to the effects of mites and the viruses they vector, in addition to being weakened due to poor nutrition. 

In recent years with the increase in backyard beekeeping in cities, I have noticed that many small-scale beekeepers prefer not to treat their colonies for mites. I wish all of our colonies could survive without having to give them any treatments. I am a strong advocate of reducing treatments in bee colonies when possible. But observing the extreme losses that backyard beekeepers are experiencing, and monitoring the very high mite levels in colonies in cities, I am starting to rethink the strategy of not treating colonies. 

Here is what happens in a city (or in a commercial beekeeping operation) when most colonies are not treated for mites. Colonies with lots of mites start to decline at the end of the season, and colonies that have been treated and have low mite levels remain strong. The strong colonies start robbing out from neighboring colonies (within 1-2 miles!) that are weak. The robbing bees carry home stored honey, and they also carry home mites from the weak colony. Soon, even previously treated and healthy colonies have high mite levels before winter, and then die off, leaving the beekeeper perplexed. 

If sufficient numbers of colonies in an area are treated, more colonies would be stronger going into fall, and robbing bees would not pick up as many mites. In other words, when more colonies are treated, horizontal transmission of mites would be reduced. This concept, of treating sufficient numbers of colonies, is similar to herd immunity in our livestock and human vaccinations. The goal of herd immunity is to bring pathogen (or mite) levels down sufficiently to reduce the spread of the problem and prevent the demise of the population. There are a number of organic and effective mite treatments available on the market. It is time to bring down the mite population in the U.S.  

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