MELISSA BLOCK, HOST:
From NPR News, this is ALL THINGS CONSIDERED. I'm Melissa Block.
ROBERT SIEGEL, HOST:
And I'm Robert Siegel.
May is the month for strawberries and for strawberry festivals in every corner of the country. But 80 percent of America's strawberries come from one state, California. Growers there typically harvest 10 times more berries from a single acre than farmers in, say, New York or Michigan. It's a miracle of agricultural technology.
But as NPR's Dan Charles reports, that technology is not as universally loved as the fruit.
DAN CHARLES, BYLINE: That California strawberry you just bought at the supermarket probably came from a tiny sliver of plant tissue that somebody cut from the tip of a growing strawberry stem five years ago. That little sliver went into a little glass petri dish and grew into a new plant, guaranteed free of disease. Then it sent out dozens, maybe a hundred, so-called runners - little daughter plants.
DAREN GEE: Those runners are basically clones of the mother.
CHARLES: Daren Gee is a strawberry grower in California. I caught him in the middle of his peak harvest time.
GEE: And then they plant those and then they take the daughters off of that one, and do it again and again and again.
CHARLES: This takes years. The plants are multiplied first in carefully-controlled greenhouses, then in fields in the heat of California's Central Valley. And finally in fields along the California-Oregon border, up in the mountains. It's cold up there, which is the key. Somehow the cold gets these plants primed for maximum production.
GEE: And then they'll dig up these mother plants and all of the daughters, and they'll throw the mothers away. And then they'll send me the daughters.
CHARLES: It's those daughters that produce California's monster strawberry crop. And all along this chain of clones, from petri dish to final harvest, people are working obsessively, fanatically, to protect these plants from disease because California's strawberry growers don't want to take any risk that their crop will fail. They have too much money invested, especially in expensive land in prime growing areas along the coast.
So every year, a month before planting, fumigation machines move slowly across the fields injecting chemicals into the soil and sealing in the fumes with sheets of plastic. The chemicals kill weeds, insects, and fungi - like a fungus that strawberry grower Daren Gee dreads called fusarium wilt.
GEE: Fusarium wilt, you can kind of picture, is like the Great White shark of the soil. It's floating around in there and then it just gobbles up your plants.
CHARLES: Now, organic strawberry growers don't fumigate; they stay a step ahead of diseases by moving from field to field. But even organic growers buy their strawberry plants from nurseries that do use fumigation.
This technology has done wonders for strawberry production, but it's under attack and it may have to change. The most powerful fumigant, methyl bromide, is getting phased out gradually because it can eat away at Earth's ozone layer. Also, regulators are telling growers to move their fields and their fumes further away from homes and schools.
Lea Brooks, from California's Department of Pesticide Regulation, says that's squeezing the strawberry fields.
LEA BROOKS: People are moving closer to farmland. And hence, the conflicts. It's so important to find alternatives to fumigants, 'cause in the future there will be additional restrictions, not less.
CHARLES: We're looking at some of those possible alternatives in a research plot near Watsonville, center of strawberry production. Dan Legard is here, too. He's director of research for the California Strawberry Commission.
DAN LEGARD: As you look at the field, it looks like a regular strawberry field. You don't see any differences.
CHARLES: The same raised beds covered with black plastic and strawberry plants poking out of holes in the plastic. But those plants aren't actually rooted in soil at all. They're growing in a foot-wide trough that's lined with fabric and filled with peat - or something called coconut coir.
LEGARD: So here's the coconut coir; it's the fibers from the outside of a coconut.
CHARLES: Yeah, looks remarkably like soil, actually.
And its wets and it has good water-holding capacity, and it mimics soil.
But it's not soil, which is the point. There aren't any scary fungi in there, so no need for fumigants to drive them away. There are other approaches, too. Using the heat of the sun to sterilize the soil or ground-up seeds of canola plants. Those seeds release a chemical that suppresses the harmful fungi for a while.
But commercial strawberry growers are skeptical about all these methods. The ones that work reliably, like growing plants in coconut coir, are really expensive. And the ones that are cheap sometimes fail.
It may work four out of five times and that looks great to a researcher, but that means 20 percent of the growers fail. And no growers is going to take that 20 percent risk when he's investing a million dollars.
So for now, most of California's strawberry growers are sticking with the chemicals. It's been a key to their success - producing more strawberries for a lower cost than anywhere else in the world.
Dan Charles, NPR News.