Olive Fruit Fly Defense

01_olive_fruit_fly_frontpage Photo credit: 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 this year. 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. So why is it so bad this year? "The best answer to why is that there is a normal fluctuation in insect populations--this just happens to be a year with a high population," University of California Cooperative Extension Farm (UCCE) Advisor, Paul Vossen. "We are also seeing a good crop, but not a huge crop and so there are more fly numbers per fruit than if you had loaded trees."IMG_4531 "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 Orchard Manager Samantha Dorsey. "For those of you who have already lost this year’s crop, keep up your pest control program to put a dent in next year’s potential OLFF population." Here are Samantha's 7 tips to help control infestation and maintain a healthy crop:twitterolives
  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 Happy harvest season to you all, and we look forward to seeing many of you at our annual olive milling eventsin late fall! For more detailed information on olive fruit fly management: http://www.oliveoilsource.com/page/olive-fly-control http://cesonoma.ucdavis.edu/files/27231.pdf http://cenapa.ucanr.edu/files/52578.pdf