Olive Fly: Time to Start Spraying


The olive fruit fly, Bactrocera oleae (Rossi) (Diptera:Tephritidae), is an important pest to be very aware of if you grow olives (Olea europaea). This pest was introduced and invaded California around 1998, and spread rapidly throughout the state and northern Mexico (Rice et al., 2003). It is very prevalent in Europe.

We are spraying our trees every other week. Some growers spray each week. Each time we spray every other row and then alternate each two weeks. I always spray each of the border trees. Not sure if it makes a difference but it makes sense to me to set up a barrier. I spray a target spot on each tree about the size of a dinner paper plate, at mid-level of the tree. I must admit that I have a great time spraying, me in the early morning, with little Casey riding along beside me. With coffee in hand and dog biscuits, we drive around the property and watch the birds and inspect each tree.

Paul Vossen is one of the leading experts in olive growing in California. His chapter in Organic Olive Production in the University of California Agriculture and Natural Resources Publication No. 3505 from 2007 is very relevant and worth reading. Along with his co-author Alexandra Kicenik Devarenne, Mr. Vossen states that this is the most economically significant pest of olives. If you spray you can save up to 80% or more of the crop. This is very economically important.

Per Mr. Vossen, “The Olive Fruit fly belongs to the family Tephritidae, a group that includes such economically important flies as the Mediterranean fruit fly (Ceratitis capitata), the walnut husk fly (Rhagoletis complete), the apple maggot (R. pomonella), and the Oriental fruit fly (Bactrocera dorsalis). Chapter 6, Pg. 47.

olive fly maggot

An adult can lay 50 to 400 eggs in a lifetime, one in each olive. As the maggot grows it eats the inside of the olive and destroys the fruit.

To prevent this destruction we spray with GF-120 Naturalyte a bait spray using the active ingredient Spinosad. Spinosad is a fermentation byproduct of the actinomycete bacteria Saccharopolyspora spinosa. Hence the name spinosad. This is a certified organic spray. It seems to have little effect on honey bees and ladybugs.

Begin spraying early and continue into the Fall harvest. We inspect each batch of olives and may reject olives that are heavily infested as this will affect the taste of the oil. And we do not want olive flies here at our Farm.

Call us if you have any questions or problems with olive fly. We can help you with some small amounts of GF-120 if you have only a few olive trees.