Olive Fruit FlyThere are a few on-going themes here at Left Coast Cowboy Land. Two of them are our never-ending fight against invasives (plants and animals) and our now two year string of unusually wet, cool weather and how it has negatively affected our normal growing seasons. I know, I know. You’ve heard it all before. How the past two springs and summers that never really came affected the tomatoes and the grape harvest.

Well, same tune, different verse. Only this time with the Olive Fruit Fly. I’m talking about that nasty customer shown to the left. It’s one of the most devastating pests to olives. Wherever people grow olives for fruit or oil — as far back as the Third Century B.C. — you’ll find woeful tales of how this guy can wipe out a whole crop. The Olive Fruit Fly is well known and feared among olive growers in southern Europe, North Africa and the Middle East. Since 1998, we in California have had to deal with it.

Cue my long-standing moaning about the two unusually wet years we’ve had. Apparently, the fly prefers cooler, coastal climates, so our rainy spring and summer provided just the conditions the fly needed to really take control. From what I’m hearing around the Valley, this past Fall’s crop was particularly hard hit. Ours certainly was. We didn’t have a large crop as it was, since our trees seem to be on an every other year boom and bust cycle. One year we’ll have just enough olives for brining for our own use, the next year we’ll be hauling bin after bin down to the Community Press. Still, what we had this year — apparently every single olive on every single tree — was crawling with Olive Fruit Fly larvae.

John the Baptist with flame thrower

John the Baptist has an ongoing war with invasives -- be they animal like bullfrogs or plant such as crimson clover. Here he takes a flamethrower to invasive plants.

We are trying to keep everything organic, but when you are planting, you bring in trees from other areas and the last thing you want to do is transport this critter onto your land. So we had been spraying under the guidance of the local Agriculture Extension Agent — who also has to certify your olives are infestation-free if you want to bring them down to the Community Press. Then last year, we switched to an experimental trap system. A lot of the vineyard managers had high hopes for it. No dice. Either it’s ineffective or it just wasn’t effective enough to counter weather that created a perfect storm of ideal conditions for the care and breeding of the Olive Fruit Fly. And considering the Olive Fruit Fly has no natural enemies in California, what was to stand in its way?

Scratch that. The Olive Fruit Fly does have a natural enemy here. We call him John the Baptist. And he Googles. Within hours of our realization that our entire harvest (small though it was) was infested, John was scouring the InterWebs for natural methods of pest control. Seems the one thing these little critters like better than olives is torula yeast. Don’t look for this in your local health food store. One article calls it “a questionable taste additive”. Apparently, it’s put in cheaper processed foods and dog chow to enhance the flavor. Although, having smelled it, I’m not sure who would find it palatable unless you like a gamey, meaty, yeasty flavor.

But, as I said, the Olive Fruit Fly loves it. And if you buy a load of $15 ball traps and bait them with the pellets, you can wipe out most, if not all of your invading flys. Or you can save the $15 per tree for the traps and do what John did. Collect as many old plastic water bottles as you can find, punch holes in them, drop in a torula yeast tablet apiece and string one from each of your olive trees.

The traps also double as White Trash Christmas ornaments!

Just a week after hanging them, they are filled with flies! Dead flies. At this rate, by harvest, there won't be any Olive Fruit Flies left to lay eggs. Success!

Now you may be musing on how interesting (or not) this all is, but you only have one or two olives in your garden for ornamental purposes. You are the person I’m talking to! Apparently, the spread of this destructive pest has been traced to ornamental, rather than commercial olive trees. See those of us who are harvesting our olives manage our trees. Those of you who just have them as landscaping are probably unaware that you even have infestations. That’s given the fly a safe haven from which to launch its invasion into California commercial olive groves.

So here’s how you can help:

  • Read and follow this helpful guide from the University of California.
  • Make sure you only buy trees from nurseries that can certify that their olive trees are Fruit Fly free.
  • Always shake down, then pick up and dispose of all fruit at the end of the season. It’s not recommended that you compost it!

Or start raiding the recycle bin, break out the torula tablets and give your spread that Trailer Park Caché!

NOTE: As ubiquitous as torula yeast is supposed to be in our diets, it’s surprisingly hard to find it. This is our source: ISCA Technologies.

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