Can the bee colonies strike back?

Colony Collapse Disorder has made such a global cultural impact it has featured twice on episodes of Dr Who, the timeless children's television programme.

Sadly, the mass disappearance of the world's bees is not the result of an incursion in time and space by the Doctor's ancient nemesis, the Daleks. Nor can it be remedied with judicious use of a sonic screwdriver. If only it were that simple.

Suspects are myriad and a new culprit is brought to the scientific dock every few months: Genetic engineering, pesticides, viruses, varroa and general anthropogenic causes. In April, ScienceDaily reported encouraging results treating a parasite, Nosema ceranae, a potential vector.

"In reality, they don't know," says Dr Mark Goodwin, the internationally recognised scientist at the bee unit of Plant & Food Research.

He is one of many who believe Israeli Acute Paralysis Virus (IAPV), so named because it was first found in the Levant, is the ultimate killer. Scientists tested about 50 hives devastated by the disorder, finding 95 per cent infected with the virus. Healthy hives have infection rates of about 5 per cent.

But, Goodwin believes it is the varroa mite that acts as the key vector, opening up hive populations to the virus's fatal impact.

"The viruses are normally in hives but they can't actually get to the bees unless the bee's been damaged in some way," he explains.

"The varroa acts like a mosquito with malaria. When the colony dies of varroa [and/or] viruses in New Zealand, what happens is you have a colony full of bees and you come back three weeks later and most of the bees have disappeared, almost like Colony Collapse Disorder."

Obviously, a cure is impossible until scientists reach agreement on what causes colonies to collapse, by which they mean the loss of about 50,000 worker bees, the average active pollinating population in any one hive.

A collapsed colony does not resemble the Marie Celeste; there is a queen, brood (bees in different stage of development) and plenty of honey and pollen. Everything else is missing.

The consequences of global collapse would be ruinous. According to US agriculture department statistics, the cost to American farmers would be about US$15 billion a year in lost production. Replicating pollination by hand, however, could impose a price tag of more than US$90b each year.

This is not as far-fetched as it sounds. In China, thousands of workers wielding pollinating feather dusters have done the job of honey bees by tickling pear tree blossoms, one flower at a time.

Honey bee pollination underpins New Zealand's economy. Without their industriousness, "all of the fruit, most of the vegetables and a lot of crops" are at risk, says Goodwin. Total fresh and processed fruit and vegetable exports fetched more than $2.9b last year, according to HortResearch. There's a big seed industry; about 80 per cent of red radish seeds and 60 per cent of carrot seed is produced here.

Bees play a role in propagating white clover, an essential element in providing the pasture to feed the $20b-plus dairy and meat industry.

Goodwin says there will always be means to treat the nation's hives, whether for viruses or varroa: "If you have enough money, you can employ the labour to do everything you need to do to control it."

But replicating honey bee pollination by hand in New Zealand would be economically untenable, as would intensive hive-by-hive treatment. Goodwin estimates everyone but hobbyists and the manuka honey beekeepers would be driven out of business.

His colleague, Michelle Taylor, is trying to breed varroa-resistant bees. Goodwin is developing a fungus, initially used to control locusts, to "kill varroa but not bees". It is for this work and other research that he was recently awarded the New Zealand Science and Technology Medal.

New Zealand is lucky. Unlike other nations, varroa in its hives have not developed resistance to two chemicals, synthetic pyrethroids, used to control the pest. This is why New Zealand hives suffer an annual death rate of 5 per cent compared to 35 per cent in the United States.

Ominously, Goodwin last week took possession of a hive from Auckland, where varroa was first established, that show signs of resistance. Scientists have been expecting this disastrous development "any day now".

Most worrying is his hypothesis that varroa is the vector for colony collapse. If the mite is now resistant, then the nation's hives will then become susceptible to the disorder.

Resistance will still take many years for resistance to spread but the scientific community now face a race against time to find an affordable, effective method of treatment or eradication. Failure to do so is unthinkable: "You can't afford to have no bees for even a year because you're saying to Zespri 'you're having no fruit next year'.

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- AAP