What’s killing the bees? Varroa, and other problems

September 11, 2013

From: Daily Caller

Randy Oliver

You only occasionally actually see them in a hive — the  pinhead-sized crablike Varroa destructor mites that have in the past seventy  years become the nemesis of beekeepers in every continent save Australia. Varroa  is indisputably the number one problem affecting bee health today.

The main problem is called the “varroa-virus complex.” Honey bees  are host to about 20 viruses, most of which were formerly considered relatively  benign. Varroa changed all that — not only does the mite vector viruses from one  bee to another (similar to how mosquitoes vector malaria), but it also injects  an immune suppressor into the bee, which then activates “latent” viruses into  bee-killing machines (similar as to how HIV induces infections to explode in  AIDS patients).

The second problem started as beekeepers worldwide desperately  sought out miticides that could be safely applied to bee hives in order to kill  this “bug on a bug.” And they worked — at first. But in a few short years varroa  developed resistance to the first two miticides, resulting in a wave of colony  losses of 50-90 percent beginning around 2004. An unforeseen consequence of  chemical control of varroa is that residues of those miticides now constitute  the most prevalent pesticides currently found in bee hives worldwide. These  residues have changed the baseline toxin load with which bees have long had to  deal — the natural plant toxins frequently found in nectar and pollen,  industrial pollutants, as well as agricultural pesticides.

Varroa isn’t the only recently-introduced parasite to be affecting  bee health. At the same time that varroa really started to be an issue, the bee  populations of both North America and Europe were invaded by the intestinal  pathogen Nosema ceranae. United States Department of Agriculture (USDA)  data indicates that its rapid increase in prevalence in the early 2000’s closely  tracked the increase in colony mortality. I’ve spent the past few years  intensely following nosema in my own bee operation, and can’t help but feel that  Nosema is also a contributor to our recent problems.

I don’t typically see nosema as being the main problem — that  distinction still belongs to varroa. The most recent USDA survey of hives across  the country found that the average varroa infestation rate in the United States  in autumn is above the danger level for virus epidemics. In any year that I hear  reports of beekeepers having a hard time with controlling varroa, winter losses  go up.

I feel that it is safe to say that the consensus of bee researchers  is that today’s elevated colony loss rate is due to several factors:

  1. The evolving varroa/virus complex, and poor mite control by  beekeepers.

  2. The added stress due to widespread prevalence of Nosema  ceranae.

  3. The recent extensive loss of good bee forage land due to changes  in agricultural practices.

  4. The forcing of bees onto cropland frequently sprayed with  pesticides, coupled with the new toxin baseline due to the miticides that  beekeepers now use to control the varroa mite (as I wrote  on Monday, the neonicotinoid seed treatments generally do not appear to be a  problem).

The latter points are a main topic of discussion by the commercial  beekeepers who manage over 95 percent of all bee hives in the United States. The  changing face of agriculture is reducing the amount of good forage lands  available to bees. Today’s farms have largely eliminated livestock, hedgerows,  and pasture land, which formerly supplied bees with abundant forage. Many  agricultural areas are now “green deserts” as far as bees are concerned, there  being precious little for bees to find to eat  in the weed-free monocultures of corn, soy, and wheat stretching from horizon to  horizon.

We beekeepers are in a difficult transition time. We happen to be  caught in the middle of both the biological evolutionary process of our bees  adapting to varroa, viruses, and nosema, as well as seeing bee-friendly  pastureland disappear at an alarming rate. We’ve been inadvertently adding to  the problem with in-hive miticides. And today’s high commodity prices are encouraging farmers to unnecessarily apply pesticides as preventative “risk  management.”

We’ll work things out. Unfortunately, it’s not going to be easy. A  number of large commercial beekeeping operations are failing. Bees and  beekeepers can use the public’s support in encouraging the preservation of  wildlife habitat on farm lands, and the planting of bee-friendly forage. And we  need to transition to more eco-friendly agricultural practices, which include  more attention to realistic  assessments of the impact of all pesticides upon pollinators.

Randy Oliver is a beekeeper and biologist. He writes at scientificbeekeeping.com.

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