Old practices and new chemicals kill bees.
Eugene marked Pollinator Week with a catastrophic bumblebee kill following the spraying of blooming linden trees with the neonicotinoid imidacloprid. To understand how and why this can happen again, a year after 50,000 bees died in Wilsonville, requires a little pesticide chemical history, and look at the politics of label restrictions.
What happened at 5 a.m. June 17, when the linden trees were sprayed, was not particularly out of the ordinary in the history of chemical insecticide treatment. Label instructions for malathion, a workhorse organophosphate insecticide, warn: "This pesticide is highly toxic to bees exposed to direct treatment on blooming crops or weeds. Do not apply this pesticide or allow it to drift to blooming crops or weeds while bees are actively visiting the treatment area."
By having the applicators at work at 5 a.m., before bees are flying, there is a significant reduction in hazard to organophosphates such as malathion because the chemical begins to degrade almost immediately. After a day or two, a site sprayed with malathion will no longer kill bees.
Malathion and its cousins, which have been around for almost 60 years, are very hazardous to humans as well as insects. Pesticide applicators have grown up learning how to balance the characteristics of these chemicals, and for the most part have been able to thread the needle between pest control and human and environmental safety.
In the late 1990s, the chemical companies invented a new class of insecticides that promised to be less toxic to people - the neonicotinoids were born, and among them is imidacloprid, the chemical implicated in the recent Eugene bumblebee kill.
The new chemistry has remarkably different properties from the old standby organophosphates. The neonicotinoids are water soluble, don't degrade very quickly, and readily translocate into plant tissue. That combination makes them work as systemic insecticides, but also means that the chemicals are active against pests and pollinators for an extended period of time.
Neonicotinoid molecules also bind almost permanently to receptor sites in the nervous system of the exposed insect.
The combination of a chemical poison that resists degradation, is incorporated into plant tissue and has a toxicity profile that accumulates in the exposed insect poses a much more challenging risk to pollinators. Particularly troubling is a recent study from Italy that shows that almost undetectable levels of neonicotinoids destroy honeybees' innate immunity to viruses.
The politics starts with the writing of label restrictions that dictate acceptable use of the products; billions of dollars are at stake.
The Environmental Protection Agency recognized the additional risks by adding two words to its standard warning.
Until recent changes in 2014 it read, "... highly toxic to bees exposed to direct treatment or residues on blooming crops or weeds... ."
Much of the debate has been about quantifying those "residues." A half-century of experience with organophosphates has been a poor guide for regulating the neonicotinoids. Is it any wonder applicators treat them similarly?
With EPA's 2014 effort to "improve" its label instructions the agency has separate restrictions for nonagricultural use: "Do not apply insecticide to plants that are flowering. Only apply after all petals have fallen off ... ." There is no mention of restrictions just before blooming, even though the systemic insecticide would remain highly effective in such a case.
Even more curious are the instructions for agricultural use: "Restrictions: ... Apply the product to flowering plants during early morning or late evening, when bees are not present" - a reversion to the standard practice used with organophosphates of applying the insecticide in late evening or early morning hours, without any mention of the danger of residuals.
Beekeepers were bewildered by this announcement. There is ample proof, with the bees still falling from the poisoned linden trees in Eugene, that neonicotinoids remain poisonous on the plants for many days. But pesticide lobbies have a strong presence at the EPA.
Our Oregon Department of Agriculture did the least it could in the aftermath of the Wilsonville bumblebee incident last year by restricting use of several neonics on linden trees.
Apparently the word never got out. Despite the fanfare about new labels that would protect us, today I went to a local store and found plenty of products containing imidacloprid for homeowners and gardens.
The ones for soil treatment had no precautions for pollinators. The sprays had the same old warnings, and nothing about linden trees.
The irony is that it makes little sense buy a rose and flower care product, when according to the EPA's own advice for the foliar version you should "not apply insecticide to plants that are flowering."
The correct language should be, "Do not apply to plants that ever flower or are ever visited by bees" - but then there would little use for a neonicotinoid with such a restriction that would protect pollinators.
Gary Rondeau of Eugene is a scientist, gardener and beekeeper. He blogs at www.squashpractice.wordpress.com.