Olive Fruit Fly Defense

01_olive_fruit_fly_frontpage Photo: Center for Invasive Species, UC Riverside

If you're a fellow olive grower, you're probably well aware that there has been tremendous pressure of olive fruit fly (OLFF) in California orchards recent years.

And if you're not familiar with these pesky little flies, they've been plaguing the olive industry since the 3rd century BC. First identified in Los Angeles in 1998, they've spread to most of California and become the number one enemy of our beloved Tuscan olive trees.

When a female olive fruit fly lays her eggs in the fruit, the larvae are left to eat their way out of the olive. The tunneled fruit deteriorates quickly, leaving oxidized oil and rotten flesh, not suitable for high-quality oil or cured olive production.


"For those of you tending a good crop this season, a proactive pest control program will help ensure high quality oil for you this year and next," says our General Manager Samantha Dorsey.


Here are Samantha's 7 tips to help control infestation and maintain a healthy crop throughout the year:

  1. Keep spraying GF-120, or some product with the active ingredient spinosad.  If you are not spraying, keep your traps up and refreshed weekly with water and torula yeast.
  2. Spray every 7-14 days in the interior of the canopy, in the morning, with a 4:1 water to product ratio.  Spray up until harvest – there is no pre-harvest interval with GF-120. Reapply more frequently if it rains.
  3. Unless you have just a few trees, do not bother harvesting already-infected fruit.  It will be expensive and time-consuming with very minimal potential results.
  4. Sort your fruit carefully when harvesting before you arrive at your mill this year.  It is difficult to mill extra virgin oil with fruit that has greater than 10% damage. At our discretion, McEvoy Ranch may ask its customers with significant fruit fly damage (>10%) to sign a waiver to this effect this year.
  5. As much as is reasonable, clean up your orchard post-harvest so as not to leave too much overwintering fruit for the flies.
  6. In the spring, set your traps out as early as April.  At McEvoy Ranch, we made five springtime GF-120 applications in April and May of this year to reduce the population before they could start breeding at pit-hardening.
  7. Remind your neighbors with olive trees that any untreated trees host the fly and compound the problem for California’s olive producers.

green olives in hand

We wish you all a healthy, fruitful growing season and harvest!

For more detailed information on olive fruit fly management:

One thought on “Olive Fruit Fly Defense”

  • I have about 9 olive trees on our residential property. Varieties include Kalamata, Leccino, Mission, picholine, a manzanillo and two cerignolas. All trees are in full bloom this year along with two Wilsonii which seem to fruit every four to five years. I began planting about five years ago with the idea of producing enough olives to cure for table use. I have yet to obtain an edible olive in spite of heavy production last year. I am unable to control the olive fruit fly. Last year I sprayed weekly with a spinosad containing product. This year, at the suggestion of a specialist, I am trying Neem oil and Captain Jack's Deadbug (lContains Spinosad - 0.001%) in combination but sprayed on separately. Is that concentration of Spinosad an effective level? Is GF-120 more effective? Kaolin has been recommended but I would rather not go that route. Any thoughts? Thanks.

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