Duane A. Lienemann,February 22, 2012 Edition
There are several reasons why honey bees are perhaps one of the most studied insects. Today’s article is going to center on a particular study of honey bees that could have huge ramifications on agriculture. Bees have captured mankind's attention and have been studied extensively since as early as Aristotle - because they are fascinating organisms. Not only because they produce honey which is the earliest sweetener human beings have found, but because of their industriousness, selflessness, and most importantly, their social organization. They actually make we humans look pretty trivial at times.
Most people probably don’t have any idea how important the honey bee is unless they, like me, love honey. If you look up the value of honey bees you would find many useful roles that they play. That means their value extends far beyond what we recognize for their popular by-product. It may surprise some that honey bees play a critical role in agriculture. The most important role honey bees play is actually not honey production, but in pollination. They are the true pollinators!
I think most everyone has heard of the decline in honey bee colonies. Honeybee populations have been in serious decline for years. Pesticide exposure is one of the theoretical factors associated with colony collapse disorder (CCD). However, incidents of CCD are typically associated with a rapid population decline in the adult bee population of a hive. Reported incidents of CCD have detected few if any dead adult bees. The United States is losing about one-third of its honeybee hives each year, according to researchers, who indicate no one factor is to blame, though scientists believe that others such as mites and insecticides are all working against the bees. Now there may be some cause for alarm in the ag sector.
The latest buzz around the beehives isn’t necessarily coming from the bees. The buzz instead involves discussion on the use of planter talc and seed treatments. A Purdue University study has shown a direct correlation between talc used in planters and honeybee deaths. It seems Purdue received reports of dead bees occurring at planting times in hives near Indiana agricultural fields during 2010 and 2011, and initially noticed that they all displayed symptoms of neurotoxic poisoning. The Purdue researchers sampled the dead bees to screen for a long list of pesticides, including insecticides, fungicides, and herbicides. Toxicological screenings showed that neonicotinoids were present in each sample of affected bees and likely the cause of death. These insecticides are highly toxic to bees; and they were found in each sample of dead and dying bees. Other bees at those hives exhibited tremors, uncoordinated movement and convulsions, all signs of insecticide poisoning from these “neonicotinoids”. You might ask, what in the heck is that? And--- why talc?
Neonicotinoids are used in popular insecticidal seed treatments such as Gaucho (imidacloprid); Poncho (clothianidin); and Cruiser (thiamethoxam) on corn and soybean seed. Almost all of the corn seed planted in North America is coated with neonicotinoids, bringing the insecticide to over 90 million acres on corn alone in the United States. These seed treatments can be present in soil for more than 2 years after they are used; they are very persistent and taken up by plants that grow in those soils. These insecticides were found virtually every place they looked, including pollen, dandelions and topsoil from unplanted fields. Imagine the flight of the honey bee and what he may find and carry it unexpectedly to the hive.
You might ask - what does planter box talc have to do with this? The problem is that these insecticide coatings are sticky and thus comes the crux of the problem. Talc is an anti-caking agent used to lubricate treated (sticky) seeds in modern planters to prevent the seeds from sticking together and ensure consistent planting. In the process, it removes and adheres to some of the material used to coat seeds. Much of this talc exits planters through exhaust fans, taking high levels of neonicotinoids from the seeds with it. Some contaminated talc exits with the seed, and about 30 percent stays in the manifold system until it's cleaned out. It can also escape when loading planters, or may just fall out of the cleanout tubes.
Researchers hypothesize that the contaminated planter box talc is responsible for a lot of the acute exposure to bees. Anyone that has cleaned talc out of a planter after planting corn can testify to the residue left in the talc. This might be why these insecticides were found in pollen that the bees had collected and brought back to their hives tested positive for neonicotinoids at levels roughly 100 parts per billion. That's enough to kill bees if sufficient amounts are consumed. Here is where the talc comes in. It seems that talc ends up with extremely high levels of the insecticides - up to about 700 times the lethal contact dose for a bee. Talc particles are very small and potentially very mobile, meaning they can easily land on flowering plants near fields, exposing honeybees. It is so concentrated that even small amounts landing on flowering plants around a field can kill foragers or be transported to the hive in contaminated pollen and kill bees at later times.
I wouldn't recommend that farmers use less than recommended talc rates as planting without talc leads to skips and doubles in the planted row. But look out, environmentalists are now calling for limiting or eliminating talc emissions during planting. They believe that this should be the first target for corrective action. We will need to make sure that we aren’t the problem. In the short term, it is important that farmers be aware that waste talc material is extremely toxic to honeybees and other pollinators. Growers should avoid cleaning out planting equipment near blooming plants (even flowering weeds) and be careful with the leftover talc in handling and disposing. Collect, don’t just dump it. Longer term, there may be other solutions. We are still in the early stages of this situation, so we will see where it leads! But for now just “bee” careful!
The preceding information comes from the research and personal observations of the writer which may or may not reflect the views of UNL or UNL Extension. For more further information on these or other topics contact D. A. Lienemann, UNL Extension Educator for Webster County in Red Cloud, (402) 746-3417 or email to: dlienemann2@unl.edu or go to the !website at: http://www.webster.unl.edu
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