Olive scourge takes flight

‘Bactrocera oleae' brings its insatiable olive appetite to California|

In 1998, a single female olive fruit fly was captured in west Los Angeles County. By 1999, olive growers in San Joaquin, Tulare and five more counties reported the fly’s presence. Today, the olive fruit fly lives in every olive-growing area in the state, waiting to ruin the olive crop at the first slip-up from the growers.

California is the exclusive olive production state in the nation. While most of the country’s olive oil is still imported from Europe and Asia, California’s olive oil production increased from 5,000 tons in 1999 to 74,000 tons in 2012, with projections still rising. California’s soil and weather are similar to the Mediterranean climate where the fruit originated, but the insect responsible for Italy’s olive destruction only recently made an appearance stateside.

In a 2014 interview published by the University of California’s department of agriculture and natural resources with Paul Vossen, farm advisor for fruits and vegetables in Sonoma and Marin, Vossen said California is ready to compete in the international oil market.

“We have about 50,000 acres of olive trees in California,” Vossen said. “Thirty thousand for oil, roughly 20,000 for table olives. With machine harvesting, we lower the cost of production, keeping us competitive with other places where there is more volume or lower labor costs.”

Sonoma County grows more than 400 acres of olive trees.

But the fly threatens to crash the newly-budding olive oil industry in California. The fly burrows into the olive when the fruit is roughly the size of a pea, and the larvae rot the olive from the inside-out. The introduction of fly larvae also exposes the olive to fungus and bacteria that could potentially destroy its flesh. Table olives cannot be salvaged from olive fly infestation. Olives designated for oil production can be saved if the infected fruit is pressed early in its life, before the larvae and bacteria destroy the flesh.

In an article by the University of California Cooperative Extension of Sonoma County, experts predict unchecked fruit fly activity could damage as much as 80 percent of the olive oil market and 100 percent of table olives.

To control the fruit fly, experts say while no California predator feeds on the Mediterranean species, it is possible to raise a parasite in culture and release it locally. To date, research is ongoing with limited success. Classic control measures include regular sanitation by removing overripe fruit that may hold fly pupa preventing landscape and ornamental olive trees from producing fruit and reducing black scale – a pest that produces a substance called “honeydew,” favorite meal of olive fruit flies. Reducing black scale populations would create a food scarcity for adult fruit flies.

Organic certified orchard farmers can make a liquid mud barrier coating the fruit, which makes egg laying in the olive skin more difficult while leaving the fruit itself unharmed.

Amy Popplewell, marketing manager at the Olive Press in Sonoma, said oil production keeps rising despite the presence of the olive fruit fly.

“We did have a smaller production than average last year, which might have been caused by a crop loss,” she said. “But today we’re receiving more olives than ever before.”

Popplewell added that the majority of their olives come from orchards in north and central California, with the highest shipments coming from Yolo County. “Nancy Cline, who owns the Olive Press, has a small orchard at their estate in Cline Cellars, but we don’t use those olives for our commercial products. As far as I know, the places we get their olives from protect their crop using the clay barriers,” Popplewell said.

In Sonoma, the biggest losers from a fruit fly epidemic would be single tree owners, who lack the constant vigilance and technology of the commercial growers. Studies by the Sonoma County Department of Agriculture suggest the fruit flies find an opening in a single, unguarded tree, and from there they can fly long distances to infect larger orchards.

“We really see the effect of these flies for the community on our Community Press Day,” Popplewell said. “In November we ask the people of Sonoma to bring their olives and make community olive oil with us to share. You get back whatever you put in. Most people don’t know what a good fruit and a bad fruit looks like, and it’s common to find infested olives on the press day.”

Popplewell said whenever they find bad fruit, the Olive Press instead substitutes their own olives from Cline, allowing people with a bad crop to continue their participation in the community press, and still go home with some oil.

“It’s been a bad year for Italy,” Popplewell said. “That’s the fly at work. We need to stay vigilant in California if we want to keep making oil here.”

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