Bee death : Maya's mitesThe death of bees can be stopped, say Berlin researchers. They breed particularly robust animals. They can be infected with parasites. Germs have less of an effect.
Collector. The antennae are electrically charged, they attract the pollen. The bees use their mouthparts to stow away the. Photo: FRANK FOX/SCIENCE PHOTO LIBRARY
Between the old fruit trees, a turret rises into the sky, the bright yellow facade of the villa is reflected in a pond. Historical beehives are on display in the park, regular customers greet each other in the honey store in the basement. But on this August day, the idyll has a scratch on it. The driveway of the State Institute for Bee Research in Hohen Neuendorf near Berlin is littered with small cadavers; even in the corridors in front of the laboratories there are dead honey bees. The death of the bees, one immediately thinks. "No, everything here is above board," ares the institute's director Kaspar Bienefeld. Workers live only 30 to 35 days in summer. And because the institute houses many dozens of hives, the number of bodies is correspondingly large.
Farmers sow and plant, bees pollinate the flowers and thus ensure a rich harvest: cucumbers, apples, onions. For centuries, this interplay between man and nature worked. Now it's hitting a snag everywhere. In the mid-1990s, the bees in a Chinese apple-growing region near the city of Chengdu suddenly disappeared. Since then, a gigantic crowd of migrant workers has been pollinating the flowers by hand. In several layers, they go from tree to tree with brushes. In the U.S., beekeepers push their hives into big trucks on order and transport them to farmers. The Californian almond harvest would be lost without them; almond trees need the flying helpers.
The U.S. Environmental Protection Agency has been complaining about the collapse of many honey bee colonies since 2006. The causes are diseases, monocultures, pesticides and the loss of genetic diversity of bees. But transporting the animals long distances also causes stress and further weakens the bees, he adds. It is a vicious circle. The lack of pollinators further exacerbates their precarious situation.
The bee trade brought the Varroa mite to Germany
In Germany, the guild is also complaining about problems with the third most important farm animal. That some insects die in winter is normal. But in recent years, most recently in 2012, it was sometimes a third of the animals. "This is unacceptable," says Bienefeld. Since 1995, the number of bee colonies in this country has continued to decline – from just under one million to a low of about 600,000 colonies in 2009.
There are several reasons for this devastating development. Many beekeepers can no longer make a living from their profession or they give up beekeeping because of their age. In addition, there is the Varroa mite from Russia.
After the Second World War, the export of bees began. Russian beekeepers in particular are interested in the Western honey bee. It not only provides more honey, but is also more reliable. The insect native to Russia, the eastern honey bee, reacts unpredictably to disease. If the brood is infested with the Varroa mite, the entire colony leaves the hive and settles elsewhere. The loss of the animals endangers the existence of the beekeepers, so they brought the relatives from the West. Through these transports the traders brought the varroa mite to Europe.
This has consequences until today. Every bee colony in Germany is now infested with the parasite. The mites develop in the brood, they suck blood and damage the animals, which then crawl out of the covered cells of the combs with crippled wings. They are susceptible to a host of other diseases that have since spread throughout the hives.
Wild bees and bumblebees are most threatened
The fungal disease nosemosis, for example, weakens the bees to such an extent that they are unable to fly and often die far from the hive. American foulbrood literally rots the brood and eventually kills the entire colony because there are no offspring. It is so dangerous that, like foot-and-mouth disease in cattle, it must be reported to the authorities. The infected insects have to be killed in quite a few federal states.
Only recently, microbiologist Elke Genersch of Freie Universitat Berlin discovered how the pathogen Paenibacillus larvae multiplies en masse in the intestines of larvae and eventually kills them. The bacterium produces the antibiotic paenilamicin, which kills the remaining settlers in the gut. "It eliminates the competition. This is an important step in the development of disease," says Genersch. So the germ has the territory to itself. Genersch was able to elucidate the molecular structure of paenilamicins, of which there are four variants, and hopes that with this knowledge, she and her colleagues will be able to develop a remedy for the disease "in the foreseeable future".
Even more threatened than honeybees are wild bees and bumblebees. Because they are not kept and propagated by humans, they are completely at the mercy of changing environmental conditions. Their genetic diversity has been dwindling rapidly for years. Especially in regions with pronounced monocultures, such as the corn-growing region of Brandenburg, fewer and fewer bees fly. Corn offers them no food, it is pollinated by the wind.
Escape to the future: researchers breed varroa-tolerant bees
"The main reason for bee mortality is the coincidence of Varroa mite, Nosema pathogens and various secondary infections with bee viruses, but also the increasing pollution of the environment by pesticides," says Peter Rosenkranz of the State Institute of Apiculture at the University of Hohenheim. His team was able to detect 20 to 30 pesticide active ingredients in pollen collected from bees. Although this chemical cocktail does not harm the insects directly. But it weakens them and in turn makes them more susceptible to disease.
Last fall, the European Commission banned pesticides from the neonicotinoid class for two years as a precautionary measure. After all, even a few nanograms can be lethal to bees. Work by several researchers had previously suggested that these agents can affect the orientation of bees. Uwe Greggers, a neurobiologist at the Free University of Berlin, for example, observed in experiments that the dance of individual bees is altered by even small doses of the pesticides.
The Landerinstitut fur Bienenkunde in Hohen Neuendorf has decided to take the bull by the horns. Researchers have been breeding varroa-tolerant bees for ten years. Native honeybees have two preening strategies against the mites: If they are infested, they perform a dance in the hive. Hastily they wiggle their abdomens back and forth. Not everyone understands the signal, and so the bee sometimes dances away for minutes at a time. But then a worker bee comes flying. Climbs onto the infected animal. It gratefully spreads its wings. Is carefully cleaned. The mite has no chance.
Small markings distinguish 2000 animals
Another behavior helps against the crawling parasites. Some bees can apparently smell which larvae are infested with mites despite the wax cover over the brood. They also sniff out other pathogens such as American foulbrood. They then open the lid with their mouthparts, drag out the infected offspring and throw them rabidly out of the hive. "If we only had bees that consistently cleaned out the cells with diseased brood, we would have solved the problem," says Bienefeld.
Among thousands of bees are often less than a handful "varroa waxy". Bienefeld's team therefore developed a method in the mid-1990s to sort out and breed these. On the thorax of the insects, his employees stick small metal plates with nail polish, which are round or variously angular. In the center is a number between 1 and 9, which is either 12 o'clock, 3 o'clock, 6 o'clock or 9 o'clock. With this marking on their backs, scientists can distinguish between more than 2000 animals.
"We always have a few dozen to a hundred animals from one colony compete against teams from other colonies," Bienefeld says. In order for the bees to be filmed by an infrared camera for five days, they are placed in a separate honeycomb in a dark box located in the institute's garden. An intern sits in the rear wing of the institute building, her eyes fixed on a monitor showing bees scurrying about. She evaluates the video footage and notes which bee with which plate on its hump has cleared the varroa-infected brood from the hive. These workers are sorted out.
A genetic test is to replace the laborious selection process
To multiply them is not easy. Normally, only the queen of a colony can lay eggs. "We use a trick, which makes us the first in the world," says Bienefeld. If the workers are left to live without a queen for three to four weeks, their ovaries develop and they can reproduce. "Of course, this does not always work. But off. Too but. The unfertilized eggs then develop into drones. This is how the best bees become fathers to the next generation." At the same time, his team is tracking which mother has had a particularly large number of children ready to fight off the disease. Researchers select these animals for mating.
Breeding is years of hard work. The best animals must produce offspring with the best, so that the genetic traits for Varroa defense continue to accumulate. "The colonies we have now are orders of magnitude more resistant to mite infestation than other honey bees," Bienefeld says. However, the parasite can still be dangerous to them. "We have not yet reached our goal."
Molecular biology methods are expected to speed up breeding starting in 2015. Bienefeld's team has identified around 20 sites in the bees' genome that are associated with increased Varroa resistance. A bit of bee blood for a genetic test could replace the costly competition with platelets on the back. Soon beekeepers will be able to buy the test in the form of a chip so that they can propagate even the best bees in their hive. "It's not enough for us to breed for varroa tolerance here. The more beekeepers who do this, the better," says Bienefeld.
The end time scenario can be stopped
Already today the institute gives its most resistant bees to breeders every year, who thus have more and more robust animals in their hives. "When we test bees from beekeepers, we see success. For the past decade or so, varroa repellency has been on the rise," says Bienefeld. The dying of bees, for some the harbinger of an end time scenario, can be stopped and contained. The researcher is sure of this.
In fact, the number of bee colonies in Germany has been increasing again for the past five years. "The trend is clearly positive," says Rosenkranz. One of the most important reasons: The media has reintroduced people to the small animal. Many young people are beekeeping, even if only as a hobby. The biggest bee boom is therefore currently experienced in the big cities. Compared to the countryside, bees find plenty of pollen and nectar in parks, on balconies, in gardens and in the linden avenues. Berlin leads the way. More than 700 colonies are now buzzing in the capital of bees, drowned out by the noise of traffic.