With the help of dirt brought by friends vacationing in the Himalaya Mountains, Iceland and Europe, scientists at the Agriculture Department have found 72 new varieties of an important soil bacterium used to kill pests naturally, without harming the environment.

Farmers spend more than $40 million each year on bacillus thuringiensis (B.t), which can be as effective at killing cabbage loopers and worms as some of the best chemicals. The new varieties of B.t appear to be more powerful than any used in the past.

"Previously, scientists thought that to get the bacterium you had to find a dead insect," said Russell S. Travers of the department's Agricultural Research Service. "We had just assumed it was an insect disease."

But the department has found that B.t is actually a normal component of many soils. They have discovered B.t's that kill caterpillars, mosquitoes and beetles nearly four miles above sea level, where there's almost no insect life.

It took scientists 85 years to identify the 24 older strains of the bacterium, but a new technique for isolating B.t from soil helped them find 72 new ones in two years.

Travers had been looking for something to help B.t change from a harmless spore to an infective one that would kill insects. He and his ARS colleagues found that when they put certain soil in sodium acetate, it isolated B.t.

They have found useful organisms in the dirt stuck on the bottom of cats paws -- which they have dubbed fluffiensis -- fixed to car bumpers and plastered to hiking pants.