Glyphosate herbicide can disrupt learning behaviour in honeybees and severely impair long-term colony performance

EXCERPT: The scientists who conducted the new study used field-realistic levels of glyphosate, similar to what honeybees may encounter on a farm growing GMOs. They found that learning behavior and short-term memory retention decreased significantly compared with the control groups.

1. New study shows honeybees harmed by herbicide used on GMO crops
2. Effects of field-realistic doses of glyphosate on honeybee appetitive behaviour

1. New study shows honeybees harmed by herbicide used on GMO crops

Judson Parker
examiner.com, 15 Oct 2014
http://www.examiner.com/article/new-study-shows-honeybees-harmed-by-herbicide-used-on-gmo-crops

One of every three bites of food we eat is from a crop pollinated by honeybees.

Yet, over the past decade bee populations have been on a rapid decline. The National Agriculture Statistics Service has reported a drop in numbers from more than 5 million to less than 2.5 million honeybees. Scientists have dubbed the phenomenon Colony Collapse Disorder, or CCD, and have been searching frantically for a cause.

A new study shows that glyphosate, the active ingredient in Monsanto's Roundup herbicide, can disrupt learning behaviors in honeybees and severely impair long-term colony performance.

Glyphosate is commonly used in conjunction with genetically modified organisms, or GMOs, which have been engineered in a lab to survive massive applications of the herbicide. The most common herbicide-tolerant GMOs grown in the United States include corn, soy, and alfalfa. GMOs were first allowed into the food chain in the late 1990s.

With the ability to blanket their fields in glyphosate, many US farmers have abandoned hand-weeding and controlled applications of the herbicide altogether. This has lead to a 527 million pound increase in the use of the chemical over the past decade.

Glyphosate's toxicity is compounded by its persistence in the environment. Many studies show that glyphosate remains, chemically unchanged in the environment, for periods of up to a year.

Recent research suggests that even when glyphosate binds to soil particles, it will cyclically "desorb" or lose its attraction to soil and become active again. A study by the US Geological Survey found glyphosate in nearly 70% of rivers and streams they tested in the Midwest.

The scientists who conducted the new study used field-realistic levels of glyphosate, similar to what honeybees may encounter on a farm growing GMOs. They found that learning behavior and short-term memory retention decreased significantly compared with the control groups.

And since bees don't die immediately when exposed to glyphosate, they bring the chemical back to the hive, where larvae come into contact with it.

This means new bees will likely have lower overall foraging rates, which could have long-term negative consequences on colony performance. In fact, it could lead to the disappearance of the colony altogether.

Although the creation of GMOs was initially hailed as a way to increase crop production and feed a hungry world, the loss of pollinators like the honeybee will have disastrous effects on the global food supply.

According to the United Nations Environment Programme, of the 100 crops that provide 90% of the world's food supply, 71 are pollinated by bees. In the United States alone, the value of crops pollinated by honeybees is estimated to be worth more than $20 billion annually.

Commercial beekeepers across the country are suffering astronomical hive losses, severely crippling their ability to meet pollination needs for a variety of crops. In fact, beekeepers have reported average annual losses of 40-50%, with some as high as 100%.

Even as honeybee colonies collapse, the US Environmental Protection Agency is set to approve the use of a new combination of glyphosate with an even more powerful agrichemical known as 2,4-D. But instead of helping farmers meet increasing demand, expanded use of the chemical could backfire. Without pollinators, the entire backbone of the US agricultural system would collapse, leaving grocery store shelves empty and residents without access to affordable, healthy food.

In many ways, the plight of the honeybee is a warning sign of the aftermath of chemically-intensive modern agriculture.

Beekeeper Zac Browning, whose commercial operation spans three states, laments that "we're just about tapped out."

"Without some real action we'll see this industry dwindle away."

2. Effects of field-realistic doses of glyphosate on honeybee appetitive behaviour

Herbert LT, Vázquez DE, Arenas A, Farina WM
J Exp Biol. 2014 Oct 1;217(Pt 19):3457-64. doi: 10.1242/jeb.109520. Epub 2014 Jul 25.
http://www.ncbi.nlm.nih.gov/pubmed/25063858

Abstract

Glyphosate (GLY) is a broad-spectrum herbicide used for weed control. The sub-lethal impact of GLY on non-target organisms such as insect pollinators has not yet been evaluated. Apis mellifera is the main pollinator in agricultural environments and is a well-known model for behavioural research. Honeybees are also accurate biosensors of environmental pollutants and their appetitive behavioural response is a suitable tool with which to test sub-lethal effects of agrochemicals. We studied the effects of field-realistic doses of GLY on honeybees exposed chronically or acutely to the herbicide. We focused on sucrose sensitivity, elemental and non-elemental associative olfactory conditioning of the proboscis extension response (PER), and foraging-related behaviour. We found a reduced sensitivity to sucrose and learning performance for the groups chronically exposed to GLY concentrations within the range of recommended doses. When olfactory PER conditioning was performed with sucrose reward with the same GLY concentrations (acute exposure), elemental learning and short-term memory retention decreased significantly compared with controls. Non-elemental associative learning was also impaired by an acute exposure to GLY traces. Altogether, these results imply that GLY at concentrations found in agro-ecosystems as a result of standard spraying can reduce sensitivity to nectar reward and impair associative learning in honeybees. However, no effect on foraging-related behaviour was found. Therefore, we speculate that successful forager bees could become a source of constant inflow of nectar with GLY traces that could then be distributed among nestmates, stored in the hive and have long-term negative consequences on colony performance.