What is Killing the Walnuts?

  A monoculture is an agricultural system that depends primarily or entirely on a single crop.  In theory, monocultures are widely acknowledged to be a bad idea, susceptible to any number of threats:  price crashes, devastating pests, diseases, etc.  And yet farmers, who are humans after all, tend to gravitate towards them.  Just like kids in high school who all end up wearing the same brand of jeans, farmers imitate their successful peers and grow what they are growing.

There are many economic justifications for monoculture as well.  If there is a big local business that buys lots of corn, for example, there is an easy market to sell to.  And chances are if that company is located in a certain area, it’s because that crop grows well there.

As I mentioned a few weeks back, the area around Winters produces a lot tomatoes — almost all of them for canning.  But one of the other primary crops here is Walnuts.  There are several reasons why.  First is our combination of deep soil, fairly high winter rainfall, and abundant water for irrigation.  Walnuts are big trees with deep roots that suck up lots of water.

Winters is also home to a very large walnut company, as well as a smaller company that is the largest processor of organic walnuts in the country.

In the past five years, the market for walnuts (as well as other nuts) has experienced huge growth as consumers in India and China as well as the U.S. have increased their consumption.  Thousands of acres of new walnut orchards have been planted in and around Winters in response to this demand and the higher prices it is creating.  So many walnuts, in fact, that certain areas have indisputably become monocultures — literally walnut trees for miles.

There are plenty of pests and diseases of walnuts, and some can heavily impact the crop in any given year.  But beginning last year, a new disease began to show up in older orchards.  This spring and summer it has spread like wildlife, killing entire branches and even whole trees.  Initially it appeared to only infect older trees of a single variety of walnut (there are several commonly grown varieties) but now appears to be jumping to younger trees and other varieties as well.

Dying walnut trees; this orchard was healthy last year.

So far, no one knows what it is.  Researchers remain convinced that it is a disease caused by a pathogen.  Others suspect that it may be related to the drought in December, or to the lack of rainfall this winter.  And everyone agrees that cutting back on irrigation, which many farmers are being forced to do as groundwater levels drop and pumps produce less water, is not helping.

Whatever is damaging the walnut orchards, one thing is perfectly clear:  farmers who have gone “all in” on walnuts are facing a potentially devastating impact to their liveliehoods.

At Terra Firma, we are used to losing crops.  We lose some every year — that’s why we grow so many different ones.  While we no longer grow walnuts, I still I feel tremendous sympathy for my walnut-growing neighbors when I drive past their orchards and see the (disease?) getting worse almost by the day.  Walnut trees normally live for up to 40 years.  As one local farmer says, when you plant a walnut orchard you don’t expect to outlive it.

Thanks,

Pablito