Mite that makes bees buzz off threatens $15bn US fruit crop

It is a sound you take for granted, the gentle buzz of bees out and about on their daily business, pollinating flowers and trees. But in the US it is a sound that is becoming steadily rarer - and that rarity threatens fruit crops worth $15bn from Florida to California.

It is a sound you take for granted, the gentle buzz of bees out and about on their daily business, pollinating flowers and trees. But in the US it is a sound that is becoming steadily rarer - and that rarity threatens fruit crops worth $15bn from Florida to California.

In the last year, up to a half of all bees in the country may have died. The culprit is the varroa mite, first identified here in 1986. The eight-legged parasite is no larger than a grain of salt, but to bees it is lethal.

The scourge is by no means confined to the US, but nowhere has it been as devastating. For a while after its arrival in the US - probably from Africa or Asia - the problem was manageable. However, the bug has now grown resistant to almost every chemical used against it.

Unless a new treatment is found, or a new mite-resistant breed of bee is developed, fruit crops including strawberries, cherries, apples, squash, avocados melons and cranberries, which to varying degrees depend on bee pollination, could be affected. Honey production has also fallen steeply.

Nowhere is the threat greater than to California's annual production of almonds - one billion pounds, or 80 per cent of total world output. Almond orchards are particularly dependent on bee pollination, and first reports are that this year's flowering was particularly poor - although this may be partly due to the cold, exceptionally wet, winter, as well as to the varroa mite.

Between 30 and 50 per cent of California's bees have died in the last year, according to growers, as the mite defies every effort to eradicate it. For the moment the shortage is being covered by emergency shipments of hives, from as far away as Australia. But that may be only a stopgap, as varroa-affected states such as Florida discover they need every one of their own bees.

Despite every effort of researchers at the US Department of Agriculture and elsewhere, the problem is growing worse. "We've never seen a crisis of this magnitude of loss of bees, David Ellingson, president of the American Beekeeping Federation, said. "It's scary."

The best hope now lies in developing strains of bees naturally tolerant of the mites, such as Siberian honey bees from Russia.