Bumblebee Kill in Eugene Rains on Pollinator Week

[Updated 6/19/14]

It is with dismay that I must report on another bumblebee kill, this time only about a mile away from the DeadBumblesbees in my yard.  All of the details are not in yet, but the basic picture is clear.  Insecticide was sprayed early Monday morning, 6/16, on blooming linden trees in an apartment complex in northwest Eugene.  Residents reported that the sidewalks were littered with dead and dying bees.  Apparently officials from the Oregon Department of Agriculture (ODA) and Oregon State University were on the scene to collect samples and initiate an investigation.  I’m sure we will know soon what was sprayed and who did it. [We know now that the chemical sprayed was imidacloprid.]

Recall that about this time last year more than 50,000 bumblebees were killed in Wilsonville.  That prompted the ODA to issue restrictions on the neonicotinoids dinotefuran and imidacloprid, banning their use on linden trees.  It is also against label directions to spray pesticides on blooming plants when there bees present.


I went to survey the bee kill scene this evening.  The ODA and OSU investigators had gone, but the dying bees were still falling from the trees.  Walking around the complex I identified eleven blooming linden trees that had been sprayed and had dead and dying bees on the ground under the trees.  [I located two more sprayed lindens, bringing my total to 13 trees; the official report is that 17 trees were sprayed.]  Under one set of three trees I counted about 300 bees on the side-walk.  Easily there was 200 more in the grass and shrubbery.  I later learned from one of the residents that she and others had swept the bees up already once and she was dismayed to continue to see them fall from the trees.  My brief survey was apparently just the more recent victims.  The eventual body count will depend significantly on what was sprayed.  If the insecticide is one of the neonics, the chemical is designed to be taken up in the plant tissues, and the trees will be lethal to bees until after they stop blooming.  If they were sprayed with a pyrethrin, then the worst toxicity will probably be gone in about a week.

That such a thoughtless act falls in the middle of Pollinator Week just illustrates how far we still have to go.  Eugene may be the first city to ban the use of neonicotinoids on city property, but that action helps little when these chemicals are actively promoted and used by thousands of homeowners, landscapers, residential maintenance companies and pesticide applicator on private lands.

All this matters to me because my bees are in range of those trees.  EugeneBumblebeeKillRight now the blackberry honey flow is still keeping most of the bees occupied, but the blackberry flowers are beginning to dry up and the bees will be looking further afield. Bees heading west from my house that find their way across the industrial railroad yard will come upon the very attractive linden blossoms.

The residents mentioned that the trees in their neighborhood often dripped a sticky mist from aphids in the summer.  Apparently, this is not the first time that the trees have been sprayed, but this year they sprayed earlier than in previous years.

Although bee kills like this one will make headlines, it is the less dramatic impact of pesticides that are even much more troubling.  Have these trees been poisoning my bees for years at sub lethal levels?  How many pounds of these toxic pesticides are spread about in my bees’ foraging range?  Is residential beekeeping doomed by thoughtless policy and people?  The pollinators are weak this week.

[On a return trip Thursday afternoon, I wanted to see if more bees were finding the site during prime foraging hours.  Indeed, I saw both bumblebees and honeybees visiting the trees, though not heavily.  Curiously, there were no honeybees on the ground, just the bumblebees.  I passed several more blooming lindens along River Road on my bike trip home. These trees were abuzz with activity, sporting ample numbers of both bumblebees and honeybees. ]


  1. Your bees might not show signs of poisoning now but you might lose them due to neonic-linked Colony Collapse Disorder in Winter, as shown in the Harvard studies by Dr. C. Lu.

    1. Yes, I actually think the problem is more related to immune collapse rather than direct poisoning. Look up the paper by Di Prisco from Italy. I have had trouble with my bees for the last two or three years. How much it involves this site, or pesticides in general, is the Big Question!

      1. Hi Doris,
        Let me explain why I’m more concerned by the implication of the DiPrisco report than with the Dr. Lu’s study. The Harvard study exposed the bees to 0.74ng/day of chemical for 13 weeks. If I convert that level of exposure to chemical parts per billion multiplied by time I get about 3367 ppb-days of exposure. That is quite a bit, so it is not surprising that the colonies died. The Di Prisco study, didn’t make as big a splash in the media, but they found that the bee’s innate immune responce to the deformed wing virus failed after feeding the bees 3 ppb-days exposure of imidacloprid. The potential for trouble with synergies with pathogens seems much more likely to me than the direct poisoning that Lu’s group measured.


        1. Gary, it’s very difficult to determine how much toxin is really taken up by individual bees in a colony under field conditions. Fact is, that the bees in Dr. Lu’s study showed no effects during and several weeks after the exposure, no immunity problems either! The colony declines only started after the onset of winter, and all the colonies which had been exposed to neonics were affected, while none of the others showed signs of CCD. A 100% correlation is an astounding result, and the delayed effect happened in both Harvard studies, so it cannot be a fluke.

        2. I’m not saying its a fluke – just that it is not an unexpected result :) I wish Lu had been dosing the bees a 10X less rate, which is more typical of field conditions. If you look at my toxicity scaling graph at (the red line for bees and assume 0.74 ng/bee/day) you will see the expected life time for such an individual bee is only about 20 days.


          Earlier in the year the queen can keep up with heavy losses and it is hard to see the problems ahead just looking at the bees. However, once the queen slows down, then older bees are more important and the colony quickly goes down.

          The only problem with Lu’s study is the dose rate was unrealistically high. Di Prisco, on the other hand…

        3. It depends on whether the bees ate the spiked sugar water solution or stored it. In Lu’s study, the bees were also allowed to forage freely, so they could bring in whatever else was available.

          Here is one way to think about it: The extra sugar water they provided was like a strong nectar flow, and the bees probably stored most of it. They only started to eat it during winter when they needed it for fuel and that’s when the effects showed up. So the dose wasn’t exactly 0.74 ng/bee/day. During the summer and fall, the dose might have been far below that. During the winter, they received a higher dose.

          This would clarify Suchail’s results–they were caged bees and spiked sugar water was all they were given to eat.

          You might want to check out our blog on this at:

          The Byrne paper cited there suggests that the bees will avoid spiked nectar given a choice. I’d like to see that hypothesis explored in a real study.

        4. You are right Susan, a lot depends of how the colonies dealt with the toxic syrup. But it’s too simplistic to assume that most of it was stored away for winter. Dr. Lu’s own interpretation is that the toxin was consumed during summer and fall and that it prevented proper “winterization” of the colonies. In general, bees prepare for winter by producing bees that have more fat and protein stores (vitellogenin) in their bodies than summer bees. If neonicotinoids interfere with the bees’ perception of the change of season then it means that they will still only produce skinny summer bees instead of fat winter bees. As these are short lived they would leave the hive to die during winter, creating exactly the picture of CCD as we have seen it so many times in the past decade: queen and a few young workers left behind with stores and maybe brood, but nearly all adult bees gone.

  2. Susan, I’m glad to see you looking explicitly at the dose levels in the paper you have on your website. There indeed may be occasional stituations where bees get exposed to residual concentratations that approach the Lu study, but I’m sure they are few and far between. I also like that you bring up Suchail, because he is the outlier on the low-dose side of the spectrum from everyone else, yet it is hard to see anything wrong with his experimental approach. In fact, if you read between the lines of the Schmuck paper that was a response to Suchail, you will again see evidence of toxicity at very low doses in one of their tests sites. My comments on that here:
    But others don’t see such extreme sensitivity to the chemicals as did Suchail. There is a contridiction. Either somebody did bad science, or there is another factor that is not controlled. I’m in favor of the second explanation, and that factor is viruses. Di Prisco’s results tell us why this matters.

    1. Gary, Nice summary of the issues in your previous post. I agree that pathogen pressure is a major issue that can make or break a colony in the presence of imidacloprid. One other possibility to consider is that the Suchail bees might be eating less because the spiked sugar water tastes bad. That would put the bees under nutritional stress as well. It would be useful to survey the literature for the amount of sugar eaten per day under different experimental circumstances to see if this idea holds up.

      1. I’m aware that there is a feeding inhibition to imidacloprid, but I think it operates at higher concentrations. DEFRA 2007 study found some inhibitiona at 40ppb and higher concentrations, but not a lower concentratins. Suchail was seeing problems at much smaller doses.

  3. Why in the >>redacted<< are companies planting these linden trees if they need to be sprayed with insecticide every year.

    I heard (and I would love to be wrong about this, anyone?) that they spray simply to stop the trees/aphids from dripping sap onto cars? I am beyond furious. What could possibly be wrong with people that they would plant these things where people park their cars if that's the case?

    I'm stunned,

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s