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When 'Patient Zero' is your backyard tree

Our producer on whether an Indian wasp can save California's citrus crop—by being introduced to residences, not farms.

July 9, 2014 4:55PM ET

by Joanne Shen @theonlyjshen

Growing up in suburban New Jersey, my brother and I guzzled orange juice by the gallon. Accompanying every breakfast, lunch and dinner, it was our beverage of choice. Mom would look for the best supermarket deals to make sure the fridge was always stocked with the good stuff. I’m not exaggerating when I say that orange juice was a way of life for us.

Decades later, I don’t drink as much O.J. as I used to. But now that I live in California, I’ve embraced another member of the citrus family—the lemon. We have a Meyer lemon tree in our yard and, boy, is the harvest bountiful. So bountiful that we can’t keep up with the fruit it produces. We’ve become experts at finding ways to use lemons—from my husband’s hobby of home-brewing limoncello to the more innocuous lemonade which my 4-year-old son both adores making and drinking.

Sadly both the cheap, plentiful O.J. of my youth and the backyard lemon tree that giveth so freely may become a thing of the past. Last fall, I travelled to Florida with contributor Marita Davison to cover a story about a disease called citrus greening that kills citrus trees—from all varieties of oranges to lemons, limes and even kumquats. Scientists are racing to find a cure—or to breed disease resistant trees—but so far, it seems like the disease is winning. Florida, the biggest producer of O.J. in our country, has already lost tens of thousand of acres of orange trees to the disease.

Citrus greening is spread from tree to tree by an insect that feeds on new growth leaves. The bug is called the Asian citrus psyllid, and it’s believed to have originated in India. Not coincidentally, oranges themselves are also originally from Asia and didn’t make it to North America until the 19th Century, when they were brought by Spanish explorers.

Contributor Marita Davison and David Morgan of the California Department of Food an Agriculture, in a greenhouse where natural predators of the Asian citrus psyllid are bred.

For this week’s episode of “TechKnow,” Marita and I decided to do a followup to our piece—this time in California, where the situation has been developing differently from Florida for a number of reasons.

First of all, the citrus green disease has only been officially diagnosed in one tree so far in the state—a tree in someone’s yard in the Los Angeles neighborhood of Hacienda Heights. (That doesn’t mean there aren’t other sick trees out there, and certainly the Asian citrus psyllid is definitely reproducing quickly in the state.)

After witnessing what Florida has dealt with, the California Department of Food and Agriculture and the California citrus industry have been on red alert; they quickly destroyed the diseased tree in hopes that any of those pesky Asian citrus psyllids hadn’t already fed on its leaves and transmitted the disease to other nearby trees.

What’s interesting about this “Patient Zero” tree is that it’s suspected that it was illegally imported from Asia, or that it was part of a smuggled citrus tree was grafted onto a healthy tree in this particular backyard. Remember those questionnaires you have to fill out on the airplane before you clear customs? It’s possible some folks haven’t quite been on the up-and-up when it comes to the question of whether they’re bringing in plants from other countries.

“Plant movement is one of the great uncontrolled systems at the moment in North America,” according to David Morgan, Environmental Program Manager of the California Department of Food and Agriculture’s Mount Rubidoux field station.

To fight this foreign invasion of both plants and insects, California has decided on a program of biological control. Mark Hoddle, an entomologist at the University of California, Riverside, went to Pakistan to search for a natural enemy to the psyllid and found one to bring back to the U.S.—a parasitic wasp species called Tamarixia Radiata. The USDA will spend $1.5 million to scale up breeding and release efforts that employ this natural strategy.

The initial battleground of this bug-on-bug combat isn’t in agricultural areas but in urban areas. Believe it or not, in California, the majority of citrus trees are in people’s backyards. The hope is to slow the spread of citrus greening before it hits major agricultural areas.

According to Morgan, most homeowners are on board with allowing the release of beneficial insects in their backyard, especially instead of using pesticides. That seems only fair—the problem originated in California in our backyards and with our American obsession with what are really, at their essence, exotic fruits.