THE BEE BOX
26
Almond Facts
JANUARY | FEBRUARY 2016
The Bee Box
CHRISTI HEINTZ
& TARA McCALL
How are the bees this pollination season? Well, we never know definitively until the pollination season
draws to an end, and hindsight will tell us if we had enough bee boxes in the orchard given our variable
bloom weather and if those boxes contained the number of bees necessary to get the job done.
We now know that mysteriously disappearing bees or
Colony Collapse Disorder (CCD) is not the problem.
Declining honey bee colony numbers and strength
has to do with many factors, including Varroa mite
infestations, mite/virus interactions, the influence of the
Nosema (a microsporidian), nutritional status of the hive,
and pesticide exposure to developing bees or pesticide/
fungicide interactions. It’s not simple, but we are more
educated about factors affecting honey bee health in
beekeepers’ day-to-day operations.
Three more recent findings are very interesting: 1)
summer colony losses rival or can exceed winter colony
losses, 2) Varroa mite proliferation has more to do with
migrating mites than the speed of their reproductive cycle,
and 3) it is not just Varroa or just viruses that best explain
a large number of colony losses, but it is the Varroa/virus
complex that is at the heart of colony declines.
In previous columns of “The Bee Box,” we have
written frequently about measures for bee health. The
Bee Informed Partnership (BIP) has provided over-
wintering colony loss data for nearly 10 years. In the last
few years, BIP has also been tracking summer colony
losses and in 2014-
2015, commercial
beekeepers lost
more colonies in the
summer than winter.
This is problematic
for almond
growers because
the industry needs
about 2.5 million strong, healthy late summer colonies
to over-winter. Figuring a loss of about 25 percent of
over-wintering bees, and the fact that not every single
commercially available colony comes to almonds, even
that huge number of colonies means supply could be tight
at almond pollination time. Summer losses might just have
a lot to do with recent findings of number two and number
three above.
Population models studying Varroa mite reproduction
show greater growth of mites in colonies than their
reproductive cycle might predict. Two different scientists,
from different labs and across the country from one
another, have come to similar conclusions. Dr. Dennis
vanEngelsdorp of BIP and the University of Maryland
and Dr. Gloria DeGrandi-Hoffman, Carl S. Hayden
Bee Lab in Tucson, AZ, both suggest that migrating
mites are the problem, not their ability to reproduce. In
our world of transporting colonies around the country
and bees sharing similar areas, not just in California for
almonds but also in the Midwest for honey production,
the possibility of bees co-mingling with other apiaries is
high. Bees can travel 3-4 miles and don’t always come
home to the same hive box.
The problem of mites drifting colony-to-colony on honey
bee foragers is only now being seriously considered
and the industry has yet to develop comprehensive best
management practices that mitigate this problem. Difficult
challenges in pollinating many different crops, including
bees being transported cross-country and also apiaries
situated in close contact with one another, do not facilitate
an easy remedy. Several beekeepers do isolate high mite
colonies to prevent them from infecting their own colonies
and keep them off trucks headed for pollination contracts.
What causes mites to drift? What causes certain
colonies to become “mite reservoirs”? Unfortunately,
honey bee scientists have yet to discover definitive
answers to these questions. But many are working to
minimize the devastation caused by this number one
honey bee pest.
Dr. Dennis van Engelsdorp,
University of Maryland,
has researched and
lectured widely on
changes in management
of Varroa mites and the
evolution of the Varroa/
virus complex now
challenging beekeepers.
All photos by Christi Heintz.
