Herbicides, Not Insecticides, Biggest Threat to Bees

AGFAX   By Bonnie Coblentz    December 17, 2015 

People who care about honeybees know that insecticides and pollinators are usually a bad mix, but it turns out that herbicides used to control weeds can spell even bigger trouble for bees.

Jeff Harris, bee specialist with the MSU Extension Service and Mississippi Agricultural and Forestry Experiment Station researcher, said herbicides destroy bee food sources.

“When farmers burn down weeds before spring planting, or people spray for goldenrod, asters and spring flowers, or when power companies spray their rights-of-way, they’re killing a lot of potential food sources for bees and wild pollinators,” he said.

Harris said the direct effect of these chemicals on bees is so much less of an issue than their loss of food supply.

“Disappearing food is on the mind of beekeepers in the state,” he said. “That is even more important to them than losses of bees to insecticides.”

Johnny Thompson, vice president of the Mississippi Beekeeping Association, is a cattle and poultry farmer in Neshoba County who has been in the bee business for the last 10 years.

“Before we got back into bees, I sprayed pastures by the barrel to kill weeds. As a cattle farmer, weeds are a nuisance,” Thompson said. “I’m trying to grow grass for the cows to eat and not weeds, but as a beekeeper, those weeds are not weeds. That’s forage for the bees.”

Today, Thompson said he uses the bush hog more than he sprays herbicides to keep the food supply for bees intact on his land.

“If you kill everything the bee has for food, you may as well go in and spray the hive directly. The bees are going to die,” he said. “All the emphasis is being put on insecticide, but the greater risk to bees are the herbicides.”

He has made management changes for the sake of his bees’ food supply, but he recognizes the tension between current agricultural management practices and pollinators’ best interests.

“When you travel through the Delta or the prairie part of the state in February, the row crop land is purple with henbit blooming. By the end of March, it’s all gone because farmers burned it down with chemicals to try to kill everything in the field before they plant,” he said.

“They burn it down early because weeds in March or early April are a reservoir for insect pests to the crops that will soon be planted,” Thompson said.

Crops in the field, especially soybeans, are great sources of bee forage, and farmers and beekeepers can coordinate to protect both of their interests. 

“We moved bees to the Delta this summer to make soybean honey,” Thompson said. “We’re working with the growers to try to put the bees in areas that are fairly protected and won’t get directly sprayed.”

But farmland is not the only place bees find food. Yards, roadsides, golf courses and power line rights-of-way are other places bees forage when plants are allowed to bloom naturally.

“We need to stop looking at them as weeds and instead look at these plants as forage,” Thompson said. “I can manage around the insecticides, but if herbicide use means there’s nothing for a bee to eat, there’s no reason to put a hive in an area.”

http://agfax.com/2015/12/17/pollinators-herbicides-not-insecticides-biggest-threat-to-bees/

Effects of Sub-lethal Doses of Glyphosate On Honeybee Navigation

The Journal of Experimental Biology   Accepted July 2, 2015

Research Article/Abstract

Glyphosate (GLY) is a herbicide that is widely used in agriculture for weed control. Although reports about the impact of GLY in snails, crustaceans and amphibians exist, few studies have investigated its sub-lethal effects in non-target organisms such as the honeybeeApis mellifera, the main pollen vector in commercial crops. Here, we tested whether exposure to three sub-lethal concentrations of GLY (2.5, 5 and 10 mg/L corresponding to 0.125, 0.250 and 0.500 µg/animal) affects the homeward flight path of honeybees in an open field. We performed an experiment in which forager honeybees were trained to an artificial feeder, and then captured, fed with sugar solution containing GLY traces and released from a novel site (the release site, RS) either once or twice. Their homeward trajectories were tracked using harmonic radar technology. We found that honeybees that had been fed with solution containing 10 mg/L GLY spent more time performing homeward flights than control bees or bees treated with lower GLY concentrations. They also performed more indirect homing flights. Moreover, the proportion of direct homeward flights performed after a second release at the RS increased in control bees but not in treated bees. These results suggest that, in honeybees, exposure to GLY doses commonly found in agricultural settings impairs the cognitive capacities needed to retrieve and integrate spatial information for a successful return to the hive. Therefore, honeybee navigation is affected by ingesting traces of the most widely used herbicide worldwide, with potential long-term negative consequences for colony foraging success.

Read at: http://jeb.biologists.org/content/early/2015/07/09/dev.117291.abstract