Supercedure: Replacing a Queen

The bees are starting to get ready for winter and several of my hives have replaced – or ‘superceded’ their queens during August.  Usually, honeybees would only replace a Queen if she were damaged in some way, or because she was getting old – after 2 or 3 years. However, many beekeepers have noticed that colonies are superceding their young queens, just two or three months after they start laying .  Currently we have no explanation for this abnormal behaviour, and as far as I know, there is no official research going on into this phenomenon. In general, the bees replace a queen if she is physically damaged (missing a foreleg for examole), if her behaviour is ‘wrong’, or her pheromones no longer satisfy the workers.  If they have a good queen who is say 2 years old, they may not want to go into the winter with a queen who will not be in perfect shape when March or April arrives.  They will not be able to produce a new, mated queen until drones are on the wing in May, so the hive decided to supercede in autumn as an insurance, so that when Spring arrives they have a new, fertile queen in full health and vigour.

Honeybees build three kinds of Queen cells:

• Swarm cells
• Emergency Queen Replacement Cells
• Supersedure Cells

Swarm cells are usually built in May – in large numbers (6 – 15 cells at a time) and usually around the edges of a frame

Emergency cells are started if a queen dies, is lost or is crushed – usually fewer in number and on the small side

Supercedure cells are built in the centre of a frame-face, usually just one or two and quite large, deeply pitted with wax

Empty Supersedure cell

I found this empty supercedure cell a few days ago in one of my hives. A virgin queen has obviously emerged from it – since the hinged cap is missing and the bees have begun to break down the mouth of the cell.  Sometimes they build empty cells, but this one has definitely had a queen emerge from it; the proof is the very tough silk cocoon which lines the cell, spun by the queen-larva before it pupated.  If you try to tear the mouth of such a cell with a knife or hive tool, it is amazingly strong and resists damage; this is a good way of checking if a queen has emerged.

New-Laid Eggs

The new-laid eggs in this section of comb show that supercedure has taken place successfully and that the new queen has probably mated successfully; final proof of successful mating will be confirmed if these cells are given nice flat-caps, proving they are worker brood.  If the cells were given domed cappings it would show that the new queen had failed to mate and was a ‘drone-layer’.

The Trouble with Queens

Many beekeepers in the UK are having problems with queens: virgin queens fail to mate, disappear on mating flights or mate successfully, only to become drone-layers within weeks. I had a good queen-rearing season and bred 6 new queens – all of which mated successfully – and all produced fertile eggs and good brood-patterns over a number of frames. However, three of these queens were superseded (replaced) by the bees within a month – which is highly abnormal; it is however a phenomenon being seen up and down the country.  Normally, a newly mated young queen would be good for at least two years, possibly three or even four – though most beekeepers try to replace their queens annually these days. However, many beekeepers are reporting that young, apparently vigorous and fertile queens are being killed by their own workers and replaced with new queens within a matter of weeks; this is highly abnormal behaviour and indicates that something is going terribly wrong.

My own hypothesis is that we are seeing the results of bio-accumulation of neo-nicotinoid pesticides in young queens which are affecting their behaviour in sub-lethal ways.  French research by Dr Bonmatin at Montpelier University in 1998-99 revealed that the neo-nicotinoid pesticide Imidacloprid kills bees when they ingest it at levels of just 3-5 parts per billion (ppb)however, his team also found sub-lethal effects at far lower levels of contamination – a mere 0.1 ppb – an almost infinitesimally small level of poison. This independent research dramatically conflicted with that of Bayer- the manufacturers of Imidacloprid – who initially claimed that their new nerve-poison only killed bees at levels in excess of 50,000 ppb; they revised this downward to 10,000, then 5,000, then 1000 – and latterly – in the face of mounting evidence they have said that it kills bees at 50-100 ppb.  Bonmatin’s research still claims that it kills bees at 5 ppb.

Why might Pesticides be Affecting Queen Bees?

Well, a worker bee only lives for 6 weeks – and sometimes less, depending on how hard it has to work in the field. So in its short life, it only eats pollen and nectar for this limited period. However, a queen bee lives for up to two years, and while a queen larva is growing in its cell, it is fed far more food than a worker larva. So if pesticides are present in the pollen and nectar which is used to feed a developing queen-larva, it will bio-accumulate far more pesticide than a worker-larva.  The levels may still be sub-lethal but since these are neuro-toxins, they affect the nervous system and brain first – which control all complex queen-activities such: as the mating-flight, navigation to and from the hive, mating on the wing, laying eggs and so on. Moreover, the nervous system controls the production of pheromones by the queen, which affect all activities in the hive.

The queen bee regulates virtually all the activities of the hive through her production of queen-pheromones, sometimes called ‘queen substance’. In reality the ‘queen substance’ is made up of a dozen or more distinct pheromones, each of which plays a vital role in the governance of the hive.  One vital pheromone for example suppresses the urge of the worker bees to produce queen cells – and hence make new queens; as the queen gets older, she produces less and less of this substance and at the same time, the population of the hive increases to perhaps 50,000 workers – so there is less and less inhibiting chemical to go around.  When the ‘queen-cell-inhibition’ pheromone drops below a certain threshold, the workers cease to be repressed and they suddenly start to make new queen cells and new queens.

However, if the queen loses her potency in terms of any of the 20 or so pheromones which she creates and distributes in the hive, the bees will sense that ‘somethng is wrong’ and they may kill and replace her.

In addition, if the queen’s nervous system is damaged in any way that affects her behaviour, her egg-laying pattern for example – the bees will kill and replace her. There have been reports from France and from America that while bee-colonies have died by the thousands in areas where pesticides are routinely used on sunflowers, oilseed rape, almonds, apples, peas, beans and so on – there have been virtually no bee-losses in areas where such pesticides are not used: forests, heather-moorlands, offshore islands, mountain districts.

I recently read about a beekeeper called Andrew Abrahams who keeps native black bees on the remote island of Colonsay in the inner Hebrides:

http://www.colonsay.org.uk/

His bees forage on the wildflowers of the ‘Machair’ – the famed coastal flower-pastures which thrive because of the calcareous shell-sands created from billions of sea-shells ground by the Atlantic waves.  The Machair habitat is found on many West-facing shores of most of the Hebridean islands and the vast carpet of wildflowers feeds millions of insects in May, which in turn attract thousands of migrant wading birds to breed here.

Since there is no intensive, pesticide-based farming on islands like Colonsay, the bees are uncontaminated – and the varroa mite has not reached the islands either, he writes:  http://www.colonsay.org.uk/honey2.html

Industrial farming has laid waste the natural bee forage of most of Britain. Hedges uprooted, every weed sprayed, grasslands fertilised by nitrogen instead of clover. Only now at the margin, in places such as Colonsay, can a wide diversity of wildflowers still be found. Colonsay and Oronsay have varied habitats from the machair near the shore, to non intensive farmland, hedges, woodland and open heather moorland. Over 50% of all British wildflower species grow in this small area. A very mixed and varied feast for the bees!. The important nectar flows that make the bulk of the honey are sycamore and bluebell in the Spring, hawthorn, bramble and clover in the summer months and then the bell and ling heathers of the autumn. But it is the fragrant nectar of the numerous wildflowers that gives Isle of Colonsay Wildflower Honey it’s unique and special flavour. The strong aromatic oils of the wild thyme, growing on the sandy machair, are just one example.

A Queen from Over the Sea

I contacted Andrew to see if I could buy one of his Colonsay Queens to create a new colony at my Apiary in the Borders, and was lucky to find that he did have some queens for sale.  The new queen would be sent through the post in a small plastic cage, protected in bubble-wrap and accompanied by a dozen or so attendant bees, with a block of honey-candy as food for the journey

The new queen would arrive a couple of days later but I had to prepare a nucleus hive of queenless bees to receive the new queen.  This is a tricky procedure, since it involves taking bees from a hive which already has a queen and separating these bees from their mother-queen, whose pheromones are the very basis of their survival.  Each queen has its own distinct pheromone-character and each hive of bees has its own ‘family-smell’; the bees will fight and kill any strange bee which attempts to enter their hive, because it does not have the right smell. So, in order to get bees to accept a new queen, with a new smell, they first have to be made queenless, by separating them from their mother-hive for at least 24 hours.

Queenless bees realise they are queenless within an hour or so, and they display all the classic signs: all normal activity in the hive stops and the bees run about all over the front of the hive in a disordered, frantic mob – ‘roaring’ loudly all the time.  This noisy-chaos  is unlike any other sight you will ever see around a beehive, and once seen it is never forgotten.

Having left this newly-made colony queenless overnight, I introduced the queen in her cage between the frames of the hive at dusk the next day.

Queenless Bees frantically searching for their queen

Queen Introduction Cage attracts bees

The effect was dramatic; within two minutes the noisy roaring died away, the frantic searching hither and thither stopped, and all the bees on the front of the hive trooped inside in an orderly manner.  As soon as the queen was introduced into the hive, signal-bees appeared on the landing board where they stuck their tails in the air and exposed the white Nasonov Gland which is normally concealed beneath their tail segment.  This exudes a ‘homing-pheromone’ which essentially signals that ‘this is home, everything is alright, come on in’.

Within minutes there was hardly a bee in sight and the Island Queen was being feted as the new mother of a new bee-colony; all that could be heard from the hive was the deep, contented hum of happy bees, which is one of the wonderful sounds of the world.

So I now  have a new queen from a pesticide-free island, heading up a new colony in my apiary.  The only problem of course is that I live in the Scottish Borders, in a centre of intensive, industrial, pesticide-laced arable farming. So the question is – ‘how long will she last?‘.

The Glories of June – Swarming

May and June are wonderful months for the beekeeper, when the colonies are expanding fast, queens are laying between 1 -3000 eggs a day and the colony is expanding rapidly.  It is also the time when bees reproduce by swarming – the colony divides and the old queen leaves to found a new colony – taking about half of the hive’s bees with her.  The swarming impulse is usally triggered by a large population increase within the hive.

Primary Swarm in my village

The queen produces many different pheromones within the hive, which govern and control the behaviour of the worker bees. Pheromones are often referred to as ‘Queen Substance’ – but in reality there are many pheromones being distributed by the queen when she is in contact with her workers.  In the early part of the season the population is small and the queen is able to distribute her pheromones alla round the hive bees and they all receive a sufficient doseage to control their behaviour.  In particular, one pheromone inhibits the production of queen cells – i.e. it stops the workers instinctively creating new queens.  However, as the population in the hive expands, there is less and less pheromone to go around, or alternatively, the queen herself is growing old, and is producing less and less pheromone.  Eventually the levels of pheromone drop below a certain level where the queen-cell-building-impulse is no longer able to be suppressed, and the workers start to build new queen cells and to raise new queens.

The old queen does not ‘want’ the workers to raise new queens but she cannot prevent them – and as soon as the new queen larvae are growing in their cells, they also start to produce queen pheromones, which in a sense ‘compete’ with the existing queen’s pheromones.  After nine days of growing in their cells, the new queens are sealed into their cells to pupate and emerge 8 days later as a new queen. On the day that the queen larvae are sealed in their cells, the old queen leaves the hive, taking roughly half of the bees with her.

New beekeepers tend to regard swarming as a ‘bad thing’ but in fact it is the annual renewal of the colony and a golden opportunity to create new colonies in the apiary.

Young Bees Building New Comb

The white eggs standing-up in the centre of these cells have been laid in the last 24 hours. By the second day they will flop-over and lie down in the cells and the larvae will then hatch and begin to grow.

Sealed Brood, Bee Larvae and Eggs: Sealed or 'capped' brood in upper left; the pearly white grubs are unsealed brood which are about half-grown. On the ninth day of growth they will fill the cells and be sealed-in; after this they spin a cocoon and pupate into adult worker bees.

Brood Nest of the beehive: This is one-frame of four or five which make up the brood nest. The sealed broed cells should be a single, uninterrupted sheet of capped cells, but there are some missing here. This is a brand-new queen and this may be a sign of inexperience; however, it may be a sign that this queen has come from stock which is becoming inbred - and genetic faults are appearing. A close-watch will have to be kept on how she develops.

First Inspection – March 19th 2009

March 18th and 19th have been warm and sunny – with a cool breeze – but in sheltered spots like my apairy the temperature has been above 15 degrees C – so it felt safe to open up my hives. I was pleased to see a queen in both hives and several frames full of eggs with larvae in various stages of development. However, there was very little sealed brood and the vast majority of the cells had eggs only one day old – so it looks like yesterdays warm weather really was the trigger for a step-change in egg-laying by the queens.  So, although I have been feeding the bees with generous amounts of syrup for the last week – and semi-solid sugar for the previous three weeks – it has not resulted in the queens laying lots of eggs.  There was very little pollen about until the last week – mainly snowdrops – but since the air temperature was so cool they have not been able to fly out to harvest the pollen.  It was interesting to see that they have actually been consuming the pollen substitute that I fed them a couple of weeks ago – but it looks like they have only begun to use it in the last week or so

Bees eating pollen substitute above the brood nest

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first-eggs-and-brood-march-19th-2009

Larvae and Sealed Brood - 19th March 2009

Biology of the Black Bee of Northern Europe

Hubert Guerriat is a biologist and beekeeper who lives in South Hainault, Belgium.  For thirty years he has been working to conserve and improve the native black bee of Belgium, Apis Mellifera mellifera, and he has an interesting website – mostly in French at http://www.mellifica.be/en/livre/

You can read his article at the link below.

biology-of-the-black-bee

Winter Losses

Visited my hives on a calm day last week to discover that  three of the five had died over the winter.  They were well fed in September and I did not take off any honey last summer – since it was obviously not a year of surplus after the appalling wet, cold summer we had. They seemed to be well-fed and I did feed sugar syrup ad-lib in September – but it looks like they died of cold and starvation.

We have had the coldest winter for the last 12 years in the UK – London had its first October snow in 70 years and we have had almost a month when the temperature never rose above zero.

Feeding sugar and honey from Ziplock Bag

The two remaining colonies were in good shape but just to be sure I gave them both a kilo bag of wetted sugar mixed with honey – fed in a ziplock bag and placed directly over the cluster. I make fine cuts in the top of the plastic bag with a razor-knife -and I used just enough honey and water to make the mixture sludgy/ doughy – but not runny – so it doesn’t drip onto the cluster.

A ziplock-bag used as a winter feeder

I also beefed up the polystyrene insulation in the hive roofs – 2″ rather than 1″ – and tacked a damp-course builder’s membrane around the hive bodies – leaving a clear entrance.  So – fingers crossed – the heavy-duty plastic will shed rainwater and keep the hives from damp, the polystyrene roof insulation should help keep them warm and the extra sugar should get them through the next week or two. I will carry on feeding until the flowers are out in March.

Winter bees feeding on sugar

I wrap my hives in a heavy-duty plastic called ‘Damp Proof Membrane’ which can be bought from builders merchants here in the UK. The plastic is about 2 mm thick and is simply stapled to the hive – or thumb tacks can be used. Once in place it sheds all the water and snow from the hive – keeping the wood dry and making it easier for the bees to maintain the temperature of the cluster. It also keeps wind out from any cacks or hive joints.

Hive wrapped in heavy duty plastic against water, snow and wind

Wasp Attack on Bee Colony

I had a small tragedy this week when a newly created hive of bees was overwhelmed by a wasp attack:every single bee was killed, all the eggs and larvae were eaten and all the honey was stolen by the wasps. The hive had been created as a nucleus with a couple of thousand young bees – which were given a queen-cell. All went well and I was pleased to find the new queen had mated and produced two sizeable patches of brood.

I saw the hive last weekend and all was well – though there were some wasps around. When I went to inspect this weekend I found a large pile of dead bees on the mesh floor – no living bees in the hive at all. There were a few dead wasps as well. The most striking thing was the hundreds of bee-wings scattered on the varroa inspection tray – and on closer examination I could see legs, heads, thoraxes by the hundreds.

wasps and bees lie among hundreds of dis-membered bee wings

I did not realise that wasps physically dis-member bees – biting off wings, legs and heads; possibly they do this to carry away the bee’s abdomens which they may use to feed their own larvae. Wasps are predators of other insects and feed their own young on insect prey. In return their own larvae excrete a sugar-rich fluid which the adult wasps feed on.

Wasps and bees lie among hundreds of dis-membered bee wings

DIY WASP TRAPS

I made 6 new wasp traps today and placed them in a ‘cordon sanitaire’ around the hives; there were dozens of wasps inside the traps within 15 minutes – so the local wasp population is evidently really high this year.

I have created a web page showing how to make wasp traps out of 2 litre plastic milk containers – at zero cost in less than 5 minutes. To download the design for the wasp trap please click below:

WORD Wasp Trap

https://beediary.files.wordpress.com/2008/08/word-wasp-trap.doc

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LOS ANGELES TIMES: BUZZZZZZ-KILL

http://www.latimes.com/news/science/la-oe-meyerhoff30-2008jul30,0,2821586.story

by Al Meyerhof, Los Angeles Times, July 30th 2008

The loss of billions of bees raises questions about our pesticide controls.

By Al Meyerhoff
LOS ANGELES TIMES July 30, 2008

“It’s likely that most people have never heard of Gaucho. And no, it’s not a South American cowboy. I’m talking about a pesticide.There is increasing reason to believe that Gaucho and other members of a family of highly toxic chemicals — neonicotinoids — may be responsible for the deaths of billions of honeybees worldwide. Some scientists believe that these pesticides, which are applied to seeds, travel systemically through the plant and leave residues that contaminate the pollen, resulting in bee death or paralysis. The French refer to the effect as “mad bee disease” and in 1999 were the first to ban the use of these chemicals, which are currently only marketed by Bayer (the aspirin people) under the trade names Gaucho and Poncho. Germany followed suit this year, and its agricultural research institute said it concluded that the poisoning of the bees was because of the rub-off of the pesticide clothianidin (that’s Pancho) from corn seeds.

So why did the U.S. Environmental Protection Agency in 2002 grant an “emergency” exemption allowing increased use of Gaucho — typically invoked during a major infestation — when only a few beetles were found in blueberries? Why did the agency also grant a “conditional” registration for its close relative, Pancho, allowing the chemical on the market with only partial testing? And why is the agency, hiding behind a curtain of “trade secrets,” still refusing to disclose whether the additional tests required of companies in such cases were conducted and, if so, with what results?

Therein lies a tale. Most pesticides, we’re told, are safe. So we add about 5 billion pounds a year of these deadly chemicals to our world, enough to encircle the planet if it were packaged in 100-pound sacks. Sure, they are regulated — but badly — under the antiquated Federal Insecticide, Fungicide and Rodenticide Act. This law allows a chemical on the market unless it’s proved to pose “an unreasonable risk,” far too weak a standard.

Gerard Eyries, a Bayer marketing manager, said in connection with the French action that “imidacloprid [that’s Gaucho] left a small residue in nectar and pollen, but there was no evidence of a link with the drop in the bee population.” Bayer also blamed seed makers and suggested that there may be “nonchemical causes” for this massive bee kill. But Bayer may not be entirely objective here. In 2006, Gaucho sales topped $746 million.

Something is killing the bees, though. Some scientists suspect a virus; others mites, even cellphones. (Bees are not known to use phones, though, having their own communications system — a dance called the “waggle.”)

Here in the U.S., the bee kill is a big problem. Domesticated bees were brought to the U.S. on the Mayflower. Today, they contribute at least $15 billion to the nation’s agricultural economy. For example, California’s $2-billion-a-year almond crop is completely dependent on honeybees from about 1.5 million hives for pollination. This year, more than 2.4 million bee colonies — 36% of the total — were lost in the U.S., according to the Apiary Inspectors of America. Some colonies collapsed in two days.

Part of the problem is how we farm. Rather than rotating crops, farmers grow the same one each year. This “monoculture” creates a breeding ground for pests. Farmers then use chemicals that kill not only the target organism but other life forms as well — like honeybees. That this approach may now be coming back to bite big-production agriculture is not without some irony. For decades the agriculture industry has been its beneficiary — with farmworkers, consumers and local communities the victims. But, actually, we’re all in trouble.

No independent government testing is required before a pesticide is registered for use. Large gaps in basic scientific knowledge about pesticides remain, including their environmental “fate” (where they end up) and their toxicity to humans and to wildlife. A problem pesticide may be removed from the market only after a long process and full trial — something that should be done before. The Food Quality Protection Act of 1996 improved control of residues in our food. That didn’t help the bees.

Rachel Carson was vilified by an industry smear nearly 50 years ago, after the release of her book, “Silent Spring.” “If we were to follow the teachings of Miss Carson,” said American Cyanamid, the maker of DDT, “we would return to the Dark Ages … insects, vermin and disease would once again inherit the Earth.” But, as Carson so eloquently put it in a CBS documentary in 1964: “Man’s attitude toward nature is today critically important simply because we now have acquired a fateful power to alter and destroy nature. But man is part of nature, and his war is inevitably a war against himself.”

Al Meyerhoff, an environmental attorney in Los Angeles, is a former director of the Natural Resources Defense Council’s public health program.

Pesticides Are Seriously Messing Up Our Honey Bees

“The Indictment Against Farm-Insecticides Is Growing More Detailed”

Kim Flottum, Editor of Bee Culture

A thought-provoking article by Kim Flottum – Editor of Bee Culture magazine in the USA which reveals that some very experienced beekeepers are convinced that neo-nicotinoid pesticides are directly involved in Colony Collapse Disorder. For full article please visit:

http://www.thedailygreen.com/environmental-news/blogs/bees/honey-bee-pesticides-55080101

ABSTRACT:

” How the Government Serves the Chemical Companies

These chemicals I’ve mentioned are all in the neonicotinoid family of insecticides. They came along after the government, several years ago, decided that the long lived pesticides had to go and better, shorter, less troublesome chemicals and integrated pest management programs had to replace them (this was called the FQPA … food quality protection act … you can sound out the letters any way you want).

Well, those long lasting chemicals were the bread and butter of the agrochemical companies and the government essentially took them away. But the government wants cheap food and there’s only one way to do that, and that’s to have good management practices, including good insect control. Very good insect control.

Long story short, budget cuts forced the EPA to cut corners and one of those corners was testing new products. Why not let the chemical companies test them, and we’ll evaluate the results, went the EPA thinking. Better: why not let the fox in the chicken house, went the thinking, and we’ll see if the chickens die.

So now the only major chemicals used to control insects on crops are in the neonic family. They are all the same, and they are all over. And all the chemicals listed here are in that family.

Do they accumulate from one year to the next in the soil, building to levels three to four times what they should be? When, after three or four years they are ingested by honey bees in nectar or pollen do they cause behavior or health problems?

There seems to be evidence that they do, but it’s only anecdotal, and science doesn’t deal with this sort of data, does it….

Dave Hackenburg has brought up a boatload of questions about pesticides. Whether they have anything to do with CCD or not is less important than if these chemicals, and their multi-season accumulations are causing significant risks for bees, or people, remains to be seen.

And what about this agrochemical complex Dave describes? What do Bayer, Syngenta, Monsanto, and others have in store for us?

Dave’s comment? “We still don’t know what’s going on, or why. But bees are dying, and we better figure it out … quick”.”

AMERICAN RESEARCH TEAM FIND 46 DIFFERENT PESTICIDES IN CCD COLONIES

Dr Maryann Frazier’s team has been studying 92 CCD colonies from all over the USA. They examined pollen, brood and wax samples from the hives and analysed them for a very wide range of insecticides, herbicides and fungicides.

They found an alarming total of 46 different pesticides in the affected colonies.

Nurse bees feeding larvae in my hives – July 4th 2008

In one single hive they found seventeen different pesticides.

The average number of pesticides they found per hive was five

Of 108 pollen samples analysed – only three did not contain pesticides.

CONCERN OVER FLUVALINATES (Bayvarol & Apistan strips)

The team found high levels of fluvalinate in wax samples from the CCD affected hives; in some case the levels of contamination were so high that they were close to the LD50 level for bees (the dosage at which 50% of exposed bees would die). The team also point out that the modern forumulation of ‘Tau-fluvalinate’ is more than twice as toxic as the original licensed product; moreover they detected an ‘amplification’ effect when a particular fungicide was present along with fluvalinate – which increased the toxicity by almost ‘one thousand times’.

Abstract:

“As found in pollen, fluvalinate, coumaphos and chlorpyrifos were the most
commonly detected pesticides with fluvali-nate and coumaphos being detected in 100% of the samples. survival. In addition, Piperonyl butoxide (PBO) (a pesticide synergist often added to formulations of pyrethroids to increase their potency) can be found in frequent use around urban apiaries. With or without the addition of PBO or other adjuvants, fluvalinate is now considered to be a highly toxic material to honey bees. Based on its prevalence in wax, wide-spread resistance in varroa and its toxicity to honey bees, fluvalinate appears to have outlived is usefulness.”

FULL ARTICLE BY MARYANN FRAZIER OF PENN STATE UNIVERSITY

WHAT HAVE PESTICIDES GOT TO DO WITH CCD? (download PDF document)

View or download the article (pdf file) by clicking on the link above.