Insects in the City

Neonicotinoids are toxic to bees and other
pollinators, especially when sprayed directly.
Applications of neonicotinoids directly to
flowering plants during daylight hours should
be avoided, per label directions.

What could present a more peaceful, bucolic image than the scene of beekeepers tending their bee hives? Beekeepers are traditionally seen as the gentlest of agriculturalists, not killing for food but merely reaping the labor of an industrious insect in exchange for nurture and protection.  Yet there is little peaceful about the verbal and political battle swirling about beekeepers and honey bees at the moment.

You may have seen the headlines in recent years proclaiming the doom of the honey bee.  The domestic bee industry in the U.S. and in other countries around the world was hit hard in 2006 with puzzling bee and colony losses, since referred to as Colony Collapse Disorder (CCD).  In a typical year beekeepers expect to lose 10-15% of their colonies to disease and various stresses.  Since CCD arrived, colony losses have averaged 30% each winter, a significant increase.  Despite dire headlines warning of the doom of agriculture, according to one 2012 report, the costs of CCD to consumers so far seem to be minimal and honey bee colony losses have been compensated for effectively by beekeepers themselves.

Nevertheless, something seems wrong with the world if bees are dying. Initially all sorts of crazy ideas were promoted about the cause of CCD, including radio waves from cell phone towers.  Since then the theories have narrowed to other, more reasonable suspects.  In the past few months some researchers and advocates have claimed that pesticides are the principle cause.  And whenever pesticides are mentioned, the debate is sure to get lively.

The USDA, university researchers and EPA have been mostly united for several years in the position that CCD is the result of multiple causes including parasites, lack of nectar source diversity, diseases, and overworked bees.  However some recent research on neonicotinoid insecticides has raised alarm bells for critics, and has even led to a temporary ban on this group of insecticides in Europe. The research in question includes laboratory studies with bees and field studies with bumblebees, thought to be more sensitive to insecticides than honey bees because of their smaller colony size.

The smoking gun for environmentalists opposed to neonicotinoids came in the form of studies reported last year that show that one of the sub-lethal effects of low exposure neonicotinoids include loss of the bees’ sophisticated ability to find their way back home. This loss of homing ability would account for one of the more distinctive symptoms of CCD, namely colonies that slowly decline with no signs of dead bees around the hive. Other forms of colony decline typically include dead bees around the colony entrance.

While there is no doubt that neonicotinoids are toxic to bees at high enough doses, scientists are still divided on the question of whether bees that forage on neonicotinoid-treated crops are exposed to high enough levels of toxicant to suffer from flight disorientation, and whether there is even a correlation between CCD and neonicotinoid use. Indeed, in some parts of the world where neonicotinoids are extensively used, such as Australia, CCD is not reported to be a problem.

If you’re a gardener, chances are that you’ve heard the dire warnings about these insecticides and are wondering if you should avoid their use.  After all, no one wants to be a bee killer.

If the scientists who study bees are divided on the cause of bee risks from pesticides, it’s likely that the answer to this question will be not be simple. But here are some points that might be useful as you consider whether these insecticides have any place in your yard and garden:

• Both the USDA and EPA recently issued a report summarizing positions that CCD is a result of multiple factors, not just pesticides.
• All labels are approved on the basis that when used according to label directions the pesticide must  not pose unreasonable adverse to humans or the environment, including honey bees.  The EPA has recently reviewed registrations for some of these insecticides and stands by its risk/benefit assessment that these products can be used safely if the label is followed.
• While research is suggestive of a potential risk to bees from agricultural uses of neonicotinoids, the case is far from proven. And so far, to my knowledge, no credible sources have suggested that urban residential uses of neonicotinoids pose any unusual risk to bee colonies in urban areas.
• The greatest potential risk to bees from neonicotinoids appears to be in agricultural settings, where bee colonies are exposed to large acreages of treated plants.  The diversity of plants and the relatively low use of pesticides in urban settings argues for lower potential risks in residential and commercial landscapes.
• Although neonicotinoids, like most nervous system toxins, are relatively toxic to birds, there is no pattern of bird deaths associated with appropriate use of neonicotinoids, as claimed by some.
• Neonicotinoid insecticides are moderately low in toxicity to people and mammals due to some unique nerve junction differences between us and insects. Just because an insecticide is toxic to bees doesn’t mean that it has broad ecological toxicity.
• Use of neonicotinoid sprays should be avoided on flowering plants during daylight hours.  Bees are at high risk when sprayed directly, or if they contact wet spray deposits.  In residential and commercial landscapes, neonicotinoids can often be applied effectively through root injection, greatly minimizing risks to pollinators like bees.

As a pest control specialist, I know that neonicotinoids are effective and valuable insecticides for a variety of pest problems around the home. For some landscape pests, especially some of our tougher scale pests and whiteflies, there are no highly effective alternatives. It’s up to all of us to ensure that these products are used in such a way that beneficial insects are protected. You can start by reading your insecticide labels carefully.  The label will tell you how to protect honey bees and other pollinators.  But a label is only useful if we read and follow them.

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What are Neonicotinoids? Neonicotinoid insecticides are a relatively new class of systemic insecticides that have grown to make up approximately 20% of the global pesticide market. The first neonicotinoid to be introduced to the home garden and pest control markets in the U.S. was imidacloprid, used for termite control, garden and lawn insect control, and even flea control (in the popular Advantage® spot-on product).  Imidacloprid, remains at the center of the CCD controversy because of its widespread use in agriculture and in the ornamental landscape market.  The neonicotinoids currently available to consumers for garden pest control include imidacloprid, dinotefuran and acetamiprid.  If you are not sure whether a product you may be using contains a neonicotinoid, check the active ingredients list on the front panel of the insecticide container.  Because neonicotinoids are systemic, and can be taken up into plant tissues, they can be applied to root zones, eliminating the need to spray.  For this same reason, neonicotinoids are not generally labeled for fruits and vegetables, unless the insecticides are barred from the edible portions by plant physiological barriers.