An expiring federal pesticide exemption could have major consequences for U.S. strawberry crops. In the latest "Speaking of Chemistry," Chemical and Engineering News explains the policy history and the scientific challenges of protecting the strawberries. (Chemical & Engineering News)

It's no surprise that delectable strawberries are highly sought after — and not just by humans. Rodents, insects, fungi and bacteria all like to pig out on the crop.

That's why the strawberry industry is facing a major obstacle now that the most commonly used pesticide is being phased out, and why researchers have put in millions of dollars in the race to come up with an alternative.

Farmers have long used methyl bromide to treat strawberries, since the pesticide was introduced in the early 1960s. But scientists identified the chemical as a contributor to ozone depletion, and in response, the Environmental Protection Agency mandated that it be phased out in 2005.

[Chevy Chase Club abandons soon-to-be-banned fumigant]

Every year since, growers have asked for and received extensions on the phaseout, but the EPA has suggested that exemptions will completely end after 2016.


Strawberries are bought and bagged at the Strawberry Festival on Saturday at the Sandy Spring Museum. (Photo by Ricky Carioti/The Washington Post)

That means industry leaders have a short amount of time to come up with an alternative, and so far, there hasn't been much progress. Other pesticides — like 1,3-dichloropropene, chloropicrin and methyl iodide — have all been found to have negative health effects on humans or to taint groundwater.

With time running out, finding the right pesticide is paramount, and scientists say it's unlikely chemicals will go away in the industry.

"We’re going to be using fumigants for a long time," said Steven Fennimore, an ecologist at the University of California-Davis who researches weed management for strawberries. "They’re relatively cheap and going all organic exposes you to a lot of pests."

When it was first developed at the University of California-Berkeley, a single fumigation was hailed to cut the use of land, water, fertilizers and other pesticides by 50 percent. Although methyl bromide became a target for anti-pesticide groups by the 1980s, the concept of fumigating crops had extended to nearly half of the nation's fruit and vegetable production. Golf courses also relied on methyl bromide to keep their grass beautifully manicured, but they lost their access to the chemical by the end of 2013.

The chemical's ousting puts a $2.4 billion industry in the United States at risk. In 2012, the United States produced more than 36 billion pounds of the berry — mostly from California — according to the U.S. Department of Agriculture.

[Will there ever be an organics label for worker rights?]

Some scientists at the University of California-Davis are working on a genetic solution, by researching resistance to soil-borne diseases. Their greenhouse has more than 1,600 varieties of the fruit, and the hope is that they can sift through and find a gene that could make them stronger. That strategy could take a few years to accomplish, though.

"As more and more land enters organic production and chemical control options disappear, breeding and clever and more sustainable production practices will be critical to the survival of the industry," said Steven Knapp, director of the UC-Davis Strawberry Breeding Program, in an e-mail. "Both are significant challenges."

Other researchers are looking into a younger concept called anaerobic soil disinfestation, or ASD. In this method, farmers create an environment that is toxic for plant pathogens. They set up a layer in the soil of water and carbon for anaerobic bacteria to form that will kill pests like fungi.

It's a promising candidate, but it's not a one-shot solution for all pathogens like fumigants.

[I had a big pain in the neck. Then I ate a bunch of tart cherries.]

Organic methods of protecting the fruit have been of interest to large commercial growers as well. Small strawberry farmers have put more of an emphasis building up the soil — as opposed to sterilizing it — by introducing cover crops, such as mustard plants. Pests like mice can also be killed with blasts of steam.

These methods are becoming increasingly important as demand for organic produce continues to rise. Still, those methods aren't surefire tactics, and growers working with large fields say steam is a useful tool, but hard to scale up economically.

"People talk about a silver bullet to replace it, and that’s a mistake," Fennimore said. "We want to put a lot of treatments together and make it all work."

Read more:

Five organic fruits and vegetables that are worth the higher cost

New EPA rule on greenhouse gases the latest blow to King Coal

Supreme Court: EPA erred in rule on toxic emissions from power plants

How to make fruits and veggies last

The rise of the avocado, America’s new favorite fruit