Updated July 03.2013
50,000 bumblebees dead in a shopping center in Wilsonville, Oregon, were killed by using a “neonic” on the linden trees in the parking lot.
Updating I lost at least three hives to pesticide poisoning. A neighbor hired a pesticide operator to spray a yellowjacket nest near my fence line– which I did not find out about until several months later. Pesticides do not always kill the bees outright, but weaken their immune or navigation systems. I lost the hives one after another, about two weeks apart.
IF you must apply pesticides, let your neighbors know so that they can protect their bees by closing up their hive for a time. Even if your neighbors do not have bees, they may want to protect their children and pets.
See the “Do not Buy List” for more about this issue.
Especially dangerous are the “neonics”– a class of pesticides outlawed in many European nations for their toxicity to honeybees and wild pollinators.
Though all pesticide and herbicide spray is hazardous to bees and most hazardous when favorite bee plants like dandelion and blackberry are in bloom and the bees are visiting them, powder is emerging as a serious hazard as well. “Neonics” are in some longlasting “weed and feed” formulas: bees furry bodies, designed to attach to pollen particles, pick these up and bring them back to their hives.
If yellowjackets are your problem, an effective way to deal with them is to trap queens with “long lasting” lures in the early spring.
Here is more discussion on the pesticides most toxic to bees and the campaign of local (Eugene Oregon) sustainable beekeepers to discourage sales of them locally.