Natural causes and neonicotinoids can explain bumble bee deaths under linden trees

Image of trees being covered with nets.

(Xerces Society) A recent study adds valuable information to the effort to understand the natural phenomenon of bumble bees dying under linden (Tilia spp.) trees. Unfortunately, recent media coverage of the study could inadvertently mislead people to believe that it is okay to use neonicotinoid insecticides on Tilia trees—a dangerous misinterpretation of existing science.

Bee-harming pesticides make migrating songbirds sick too

Image of white-crowned sparrow in researcher's hand.

(CBC) White-crowned sparrows that ate a tiny dose of the neonicotinoid imidacloprid — equivalent to a just a few coated seeds and far below the lethal dose — lost their appetite, quickly lost weight at a time when they should be fattening up and delayed their migration to their breeding ground by several days. That delay could potentially reduce their success at breeding at a time when bird populations are falling across North America.

A new way to assess the danger that pesticides can pose to bees

Image of female hoary squash bee.

(The Bee Report) Discussing the hazards that different pesticides might potentially pose to bees can be a frustrating and tricky thing. The problem is that risk assessments are done with honey bees. And the honey bee is by no means representative of the roughly 3,999 other bee species in North America. Sure, a certain dose of a certain chemical under certain conditions might not kill off a perennial honey bee colony with tens of thousands of individuals. But what would the effect be on a single bee who is alive for only six weeks, raising her brood of eight? Especially when the greatest exposure to pesticides can come from the soil.

Pesticide widely used in US particularly harmful to bees, study finds

Image of honey bees.

(The Guardian) Agriculture in the United States has become 48 times more toxic to insects over the last 25 years, largely due to neonicotinoid pesticides, according to the study. “We have not learned our lessons… There’s this fundamental recklessness and foolishness to introducing [neonics] and continuing down this path,” says Kendra Klein, an author of the study and a senior scientist at not-for-profit Friends of the Earth. The study can be found here.

This tiny insect could be delivering toxic pesticides to honey bees and other beneficial bugs

Image of mealybugs on a leaf.

(Science) A common pesticide may be causing more collateral damage than thought. According to a new study, neonicotinoids can kill beneficial insects such as honey bees, hoverflies and parasitic wasps by contaminating honeydew, a sugar-rich liquid excreted by certain insects. This can devastate more insects across the food web than nectar contaminated with insecticides could, the research team says, because honeydew is more abundant, especially in agricultural fields.

Adjuvants amplify the toxicity of pesticides on honey bees

Image of researcher among yellow flowers.

(EurekAlert/Society of Environmental Toxicology and Chemistry) When applied alone, adjuvants – chemicals commonly added to pesticides to help them spread, adhere to targets, disperse appropriately, prevent drift and so on – caused no significant, immediate toxicity to honeybees. However, when the pesticide acetamiprid was mixed with adjuvants and applied to honeybees in the laboratory, the toxicity was quite significant and immediate: the mortality was significantly higher than for control groups. Additionally, flight intensity, colony intensity and pupae development continued to deteriorate long after the application comparative to the control groups.