Without Methyl Bromide, Then What?

 By Brian German, Associate Broadcaster

Methyl bromide was first identified as an ozone-depleting compound in 1991 and was scheduled to be phased out by 2005. California strawberry growers found it irreplaceable and fought for exemptions that allowed the fumigant to be used through 2016.  Mark Bolda is a UC Cooperative Extension Farm Advisor who specializes in strawberries and caneberries and also serves as the County Director for Santa Cruz County.  He discussed the work being done to find an effective alternative to methyl bromide.

“It’s not just one thing does it all; it’s going to be one thing and then you add other things on top of that. … We don’t have the silver bullet anymore; it’s gone.  We need to figure it out using the systems approach,” Bolda said.

The inability to use methyl bromide is causing some concerns for strawberry growers, who are looking at what new type of management approach to take.  “Everybody’s familiar with the concept of integrated pest management for insects, and really, we need to approach this post methyl bromide era using integrated pest management,” Bolda said.

Growers are worried about how vulnerable their crops are going to be to various soil diseases without methyl bromide, as researchers have yet to find an alternative that is equally effective.  One of the ways to combat disease is to focus on the details of planting.

“In strawberries, you have different chill times. You know, if you add cold conditioning, you give the plant more vigor. The colors of the plastic that you’re using to manage the temperatures of the soil, the amount of fertilizer that your using, all of these things now, we need to start to integrate into the way we are growing the strawberries,” Bolda said.

Methyl bromide controls a variety of pests in agriculture.  It was also commonly used to treat commodities like grapes, asparagus and other imported goods to prevent introducing pests to the U.S.  Bolda expressed disappointment in the lack of preparation in finding an adequate replacement for methyl bromide. “Here we are, zero hour, and we don’t have this worked out. I think, to some extent, there’s been a lack of leadership in the industry,” Bolda said.

The quest for replacing the fumigant might have gotten a late start, but industry experts have been working double-time to find solutions. “We have got all of the researchers in this industry together, working as a unit, and there’s a lot of smart people working on this problem right now. …. What do we need to research? What do we know? What do we not know? Let’s go,” Bolda said.

Nearly 90 percent of methyl bromide use in California was for pre-plant soil fumigation in strawberries, nursery crops, grapes, and tree fruits and nuts.  Growers are preparing for a 5 to 10 percent drop in yield as a result of methyl bromide’s absence and are looking for ways to make up that deficit.

“Maybe using more precise fertility practices, adding cold conditioning to the plant, taking it away, using different varieties.  All of this is going to start to go into this system,” Bolda said

The phasing out of methyl bromide is most impacting to the strawberry industry, which is California’s third most valuable crop behind almonds and grapes, with annual farmgate sales of $2.5 billion dollars.  The biggest disease threats to strawberry fields are macrophomina phaseolina and fusarium, which can both have devastating results in crops.  “It’s plant collapse. You’ll see it kick in once the plant loads up in fruit and gets a little warm. It’s just too much stress for the plant,” Bolda explained.

Methyl bromide will be missed by growers, but its absence is allowing them to demonstrate their creativity in finding new solutions to a problem. “We’re starting to see some methods that are pretty interesting,” Bolda said. One such method is steam, which involves pushing steam into the soil to kill certain pathogens.

Breeding in resistance to disease can also be beneficial; however, it can have some negative consequences as well.  “When you have strong tolerance, you’re taking a hit on something else. There’s no such thing as a free lunch. You might have a plant that’s super resistant but then the yields are low, it doesn’t fruit until late. There’s always the trade off,” Bolda said.

Getting a good chill before planting can also be effective in making the plant more vigorous and better able to withstand disease pressure.  “It’s a little complicated because the longer you chill, the later you’re planting times get, and if you’re planting in the middle of December, [there’s] not a light of sunlight in the middle of December, so you know, there’s a trade off there too,” Bolda said.

Crop rotation can also assist with some soil diseases, but more research is needed to determine just how effective it is.

Methyl iodide was showing some success as a possible replacement for methyl bromide, but its use became a problematic issue.  “It became a political problem. I don’t think the industry stood it’s ground on it, and the industry, basically they struck their flags and left the field. Of course, the entire problem was defined by the opposition,” Bolda said.

Growers might have some difficulty working out a new pest management program without the use of methyl bromide, but Bolda explained that understanding the problem at hand is an excellent step in the right direction.   “Don’t just turn scientists loose and just say, ‘study and do experiments.’ No. Define the problem. I think what we’ve done with the fumigants over this last two years. Getting everybody together and working as a unit, we have defined the problem and now that mental energy and that mental potential is moving. You need to define it in order to bring the people in to solve it,” Bolda said.

It’s going to take some time to work out a program that best replaces methyl bromide, but Bolda is optimistic about the future.  “Sometimes the solutions aren’t so obvious, but they’re starting to show up and you know, the thing is that some of these will be radically different,” Bolda said.