The Eternal BattleDel Stewart

Agriculture has always been an ongoing battle, and the enemy is pests that destroy crops. Modern agriculture is more and more a balanced coexistence with many pests, but it’s as much of a struggle as ever.

Agriculture itself begins by tipping the scales in favor of the pest. Human civilization in general benefits pests, which have moved from their natural habitat to our back yards along with us. “If you’re in your home landscape, though, you have this whole variety of plant material so the pest doesn’t become overwhelming,” says Eric Larson, Executive Director of the San Diego County Farm Bureau. “Now you’re a farmer and you’re growing one particular item over a large scale.” Any pests that attack that item becomes a large scale infestation as well, he explains.

Farmers have the same pests that home gardeners have—ants, snails, aphids, mites, grubs—and some that we don’t. Even on the small scale that we understand, though, the stakes are high. “For instance, we all have brown garden snails in our gardens, and we squash them and we otherwise deal with them,” Larson says. “However, a nursery can’t have one. If they’ve got one, and it goes out with the shipment, then the shipment gets rejected. It’s a zero tolerance level for shipping agricultural products.”

Chemical remedies for farmers are getting less popular, and not only for organic farms. Most growers implement a strategy now called I.P.M. “Integrated Pest Management,” says Larson. “The basic idea of I.P.M. is rather than going out and just using a boatload of chemicals to kill insects, you attempt to break the life cycle at the vulnerable point.” The organic farmers have to take I.P.M. up a notch simply because they don’t have the chemical alternatives that non-organic farmers do. Even when chemicals are used in an I.P.M. strategy, instead of poisons that kill the pest, they are designed to stop it from moving from one life cycle to the next. “It doesn’t kill it, but they don’t mature,” says Larson. “And they don’t get to breeding age.”

Larson stresses the point that most agricultural pests are not native to San Diego County. In this arid climate, there are few if any. When the subject turns to pests that are not yet here in a way in which they can sustain themselves, such as the Mediterranean fruit fly, the light brown apple moth, and the Asian citrus psyllid, we can turn to our constant personal battles with snails and aphids to see what might happen if we lose the battle to keep these new pests out of the county. The idea of the quarantine system is to stop these new pests from gaining a foothold here and becoming established, which would be a disaster for our local agriculture, not to mention our back yards.

As of January 2011, there are two quarantines in the county. One for the psyllid, and one for the apple moth. While the psyllid is a pest exclusively to citrus plants, “the apple moth is not a picky eater,” according to Larson.

Though the psyllid doesn’t bother the fruit itself, it’s still “the most threatening quarantine we’ve ever had in my experience in San Diego County,” says Larson. “The pest does not cause an immense amount of damage, however the psyllid is a very efficient vector of a disease called huanglongbing or citrus greening. Anywhere this disease has occurred in the world, they’ve been unable to control it, and a tree that gets the disease will die. They have it in Florida and they’ve lost several hundred thousand acres of trees already.”

Huanglongbing or Citrus Greening Disease

So for this particular pest, the psyllid is the advance guard and arrives first. If we can stop it, we can stop the disease, which is present in Mexico and the Southern U.S., but not yet in California. The psyllid, however, has been found in virtually every California county.

And the foundation of that effort is the quarantine. Each pest has a different quarantine trigger, having to do with whether it’s likely to breed. An apple moth was discovered in Bonsall last summer, but did not trigger a quarantine because only one was found. The quarantine was triggered for the moth last fall when two were discovered in Balboa Park.

Also, a mated female or larva stage pest will trigger a quarantine, even if there’s only one.

There were actually four medfly quarantines last summer, moving from South County up to North County. These quarantines were “judged successful and completed,” Larson says.

When you find a quarantineable pest, you draw circles around the place where it was found, one to three miles or so depending on how far the pest can move on its own. This is the quarantine area. The treatments are done by the California Department of Food and Agriculture and the United States Department of Agriculture. “The thought is that you want to attack a quarantine pest where you find it,” Larson says, “so that it doesn’t spread to the rest of the state and the nation.”

The treatment for those quarantines was using a sterile fly release technique. This means they release millions of sterile male flies. Since the females only mate once, they are vastly more likely to mate with a sterile male and fail to reproduce, which breaks the life cycle and eventually eradicates them from the area.

Needless to say, the farmer caught in a quarantine area can be in a world of hurt. Generally speaking, the farm where the pest is found has to strip its fruit or destroy its crop. The other farms in the quarantine area have the option to treat their crops. The treatment insures that the pest cannot exist on the farms or in their products. Often, as for the medfly, treatment means not letting the fruit leave the quarantine area fresh, or in other words, processing it in some way that any medfly in any stage of its life would not survive.
Some quarantine treatments are less drastic. The citrus psyllid requires that the fruit be washed before it leaves the farm because the psyllid doesn’t travel well on the fruit (it much prefers the leaves).

“There’s a role for the public,” Larson says. “There’s a reason why, when you come into California and you go through those inspections stations” you have to discard any fruit that you have. Although there is a land bridge between San Diego and both Mexico and the Southern US, the desert acts as kind of a barrier to keep these pests and diseases out. Just about the only way for them to overcome that barrier is if people to bring them in by car, or ship them. “Don’t pack a pest,” Larson states emphatically. “Though not proven, the assumption is that we got the Asian citrus psyllid because someone brought a tree in illegally from Mexico. And the disease itself is only as far away as it takes someone to drive here from an infected area.”

San Diego grown food on San Diego plates is more than just a miracle of nature. It’s also a series of natural and man-made challenges overcome. Farms and ranches are, above all, businesses, and as with any other business, those challenges translate into financial hurdles. As central as food is to our existence, that connection can’t be broken. Our patronage of locally grown and raised food is our second role to play in maintaining and enhancing San Diego’s position as a Foodie Paradise on Earth.