With Almond Bloom in Full Swing, Bees Are Struggling to Emerge from Winter

Thursday, February 18, 2016
By: Dick Rogers, Principal Scientist/Entomologist of Bee Health and Integrated Apiculture Research
Honey bee pollinating winter white flower

In November I wrote about how I was concerned that it might be a rough winter for bees due to unusually high Varroa mite counts.  One commenter on the post summed up many people’s feelings when he said he was “hoping for the best for the bees in 2016.”

The California Almond Industry and Honey Bees

Almond season is now in full swing in California, and we’re starting to get reports about how rough a winter it has been.  The almond crop requires more than 2 million honey bee colonies for pollination, more than half of all the hives in the U.S. 

Gordon Wardell, chairman of Project Apis m., a non-profit dedicated to bee health, wrote in their January newsletter about challenges facing beekeepers on the eve of almond season. He explains that “Record losses [of honey bee colonies are] being reported across the country - some estimate losses in their operations as high as 40% to 60%...Everyone's numbers are down.”

Almond tree in full bloom from pollination

An almond tree in full bloom.

Wardell also says that it is “a testament to the proficiency and tenacity of our nation's commercial beekeepers” that a shortfall of colonies is not expected this season even with the increased demand for pollinating units. Thus, California almond orchards are currently full of honey bee colonies from across the country, sufficient to support such a large almond yield.

The Varroa Mite Challenge

As I noted in November, this outcome isn’t surprising given that we’d seen Varroa levels in many colonies three times higher than what is considered dangerous for colonies.  Unfortunately, once a colony is seriously infested there is very little that can be done in the late fall and winter to prevent the negative effects of the infestation.  That’s probably why several commenters were looking more to the future to discuss options for combating Varroa in their hives.

Varroa mites are difficult to manage. They reproduce in sealed honey bee brood cells, grow quickly in number, and are difficult to assess visually in hives. Furthermore, previously highly-effective treatments are no longer providing adequate defense; beekeepers and researchers suspect the mites are becoming increasingly resistant to popular treatments. 

Worker honey bee with two varroa mites on abdomen

Newly emerged worker honey bee. Note deformed wings on left side, and two Varroa mites on the bee’s abdomen. A healthy winter bee can live for several months, but mites and viruses have compromised this bee’s health, meaning it probably will not live more than a few days at most.

One new product, Oxalic acid, has been available to beekeepers in Canada for many years, but is only recently registered in the U.S. and seems to be effective for control of Varroa during the late fall or early spring when little or no brood is present.  However it is also important to reduce Varroa numbers using other products in late summer to protect the winter bees that are produced starting in August. 

The irony with Varroa is that outbreaks are worse in strong colonies and build up very quickly during August and September in most regions. Beekeepers often get caught off guard by this.  One commenter to my post noted that “2015 for me has been the healthiest bee year since 2003, no virus diseases and at the beginning of August a low Varroa infestation degree.” Hopefully, follow up monitoring confirmed this condition continued into the fall months.

Prepare for the Rest of the Year

For beekeepers who had strong colonies through summer, my simply stated rule of thumb for Varroa forecasting is that “Varroa mites do best in strong colonies”. Anyone that feels their colonies are healthy because they are strong, but who does not monitor their Varroa levels, should be prepared for a big surprise in the fall through spring period. Close monitoring of Varroa numbers in late summer and early fall is essential, and having effective treatment options available is critical.

For the honey bee that survived to January and a trip to California, the milestone million acres of almond flowers blooming must seem a bit like waking up to Thanksgiving dinner, but with two million colonies arriving all at the same time, there is a lot of competition for the almond flower nectar and pollen.  Meanwhile, the beekeepers must continue the constant challenge to prepare for the rest of the year.

Thermal image of a Bayer Bee Care Center research hive

Thermal image of a Bayer Bee Care Center research hive as of Feb 9. The cluster looks large and the colony is expected to survive the short North Carolina “winter”. We will use thermal imagery to assess all the hives in our main research apiary soon.

To help them, the Honey Bee Health Coalition facilitated the production of a Tools for Varroa Management guide. “This Guide explains practical, effective methods that beekeepers can use to measure Varroa mite infestations in their hives and select appropriate control methods.”  And we’ve just announced a $1 million effort with Project Apis m, called Healthy Hives 2020, which will, among other things, fund research into Varroa.

Please leave a comment below or visit BeeHealth.Bayer.com if you have any additional questions about Varroa mites or bee pollination.



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