Wednesday, August 14, 2013

Does Wearing Perfume Confuse Bees?

This weekend, the following snippet in the Oregonian's Home and Garden section caught my eye.

Another reason to avoid artificial fragrance: It can confuse bees. Bees are vital to the natural world  thanks to the important work they do to pollinate flowers. They are attracted to the sweet-smelling scent from actual flowers, and are also attracted to artificial scents found in body washes, perfumes, shampoo, air fresheners and scented candles. This confusion by bees can lead to fewer pollinated flowers. One way to help is to choose fragrance-free options whenever possible.

-- Danny Seo, eco expert, Universal Press Syndicate

Is this really true? Will my locally-sourced and produced lavender soap draw bees away from the real deal?

As someone who uses lavender-scented soap and a kukui-nut scented lotion, could I be responsible for the current pollinator crisis?

Not likely. Bees find flowers by scent, but they also orient by sight. And, bees are remarkably good at 'remembering' which floral visits were profitable and which were a waste of time.  In tests of honey bees, they performed remarkably well at discriminating among similar scents, to hone in on the scent that was previously associated with a 20% sucrose reward.  Of the 1848 odor pairs, the bees were able to choose the 'reward' scent' 97.0%  of the time (1793 odor pairs). Only seven odor pairs (i.e. 0.4% of all odor pairs) were not distinguished by experimental bees trained to a given scent.  The other 2.6% of scent 'failures' (48 odor pairs) could be attributed to a single poor-performing bee.

Other studies of solitary bees have found that you can get a response from their antennae to certain scents, but that this doesn't mean that they'll visit the source of the scent.  Visual stimuli (how a flower looks) and previous floral rewards (if a flower gives nectar and/or pollen) matter.

So . . . even if we use scented shampoos, lotions, etc., we don't really look like flowers, and we probably don't provide a nectar reward.  Bees are unlikely to be fooled.

My favorite test of this topic was presented at the 2009 annual meeting of the Entomological Society of America, by my friends John Carlson  and Mark Fox.  The abstract of their presentation, entitled 'Is that a person or a flower?  Experimental evaluation of the standard recommendations given by physicians to venom-allergic patients regarding foraging Hymenoptera'.
Could this shirt put you at risk? Photo Credit:  Dayna Inc., the UnHawaiian Shirt Company.

Physicians give patients with life-threatening allergies to Hymenoptera venom, advice regarding avoidance of defensive stings as well as avoidance of foraging workers. Some of this advice is in contrast to recommendations given by USDA and other organizations that employ entomologists: avoid wearing bright colors, floral patterns,and perfume that might attract foraging insects. The likelihood of a bee or wasp to alight upon clothing was tested in haphazardly chosen locations around New Orleans, LA over the summer of 2009. Dark clothing and bright, floral patterned clothing were placed on the ground and observed for 10 minutes. Perfume was applied to all clothing for a second 10 minute observation period. Control plots were observed during each replicate to ensure that foraging Hymenoptera were active on flowers at the location. No species from which allergy has  been reported alighted on any article of clothing for the duration of the study. These results were expected based on the known sensory cues used by social Hymenoptera in locating food. In light of these findings, venom-allergic patients should not be advised to avoid perfume or bright clothing, especially because dark clothing has been associated with stings from workers defending honey bee colonies.

Mark and John used perfumes with the highest concentration of natural floral scents.  They purchased the gaudiest floral shirts they could find ~ as well as shirts with 'realistic' looking flowers.  Alas, the shirts did not receive any bee or wasp visitors.