It’s a good time to think big when it comes to growing table olives in California, and fewer trees this year are going into the ground in the state to produce olive oil.

But production of olive oil in California is expected to nearly double over the next few years. And both industries have a common enemy — imports of questionable quality.

Those were among observations at a University of California program in Tulare where participants also heard the latest on mechanical harvesting, olive knot and verticillium management and use of olive mill waste water for nutrition and for management of olive diseases and insect pests.

“There are three easy answers to an inventory that’s out of balance: Big fruit, big fruit, big fruit,” said Adin Hester, president of the Olive Grower’s Council of California in Visalia.

Hester opened the program with a look at the black olive industry in California and a continuing decline in acreage: He said it’s now at “25,000 acres, maybe less. S&J Ranch, for example, has cut 750 acres and gone from being a major grower to a small one.”

But this is an “on” year for the olive industry in which fruit production alternates between large crops in an “on” year often consisting of smaller, lower value fruit and smaller crops consisting of larger, higher value fruit.

(For more, see: Large olive crop may benefit from chemical thinning)

A strong example of that is last year’s crop of almost 27,000 tons compared to the year before when the tonnage was nearly 165,000. Hester said nearly half of that 2010 crop was smaller sizes, and he described production in four of the past six years as “crop failures.”

Hester said the industry remains threatened by imports, particularly in the food service arena “where consumers don’t have a choice.” His point: Given a choice in the supermarket, the consumer may decide to bypass the imports.

The state’s olive oil industry shares the import pain. Olive oil producers in California last year accounted for 1.5 percent of the olive oil consumed in the United States, said Dan Flynn, executive director of the UC Davis Olive Center. The state’s production was 1.2 million gallons, he said, compared to 78 million gallons that was imported into the country.

Flynn said the rush to plant trees for oil has slowed: “There’s not much going into the ground this year.” But production continues to climb, he said, with the expectation that this year’s production will total 2.5 million gallons, and that California production will hit 5 million within the next three to four years.

Flynn said the producers of oil and table olives share the threats from lower quality imports, along with subsidized competition. In addition to subsidies within competing countries, he said, there is also some U.S. support for competitors. He cited an example of aid to Morocco.

Flynn said the Davis center is pairing a chemist at the UC campus with a plant scientist to look at the chemistry of olives and do research on data that could show quality differences. He said chemical methods of analyzing quality “can help enforcers of standards make sure that bad quality [fruit or oil] is not making it to the market.” That could help U.S. Department of Agriculture inspectors.

The Davis center is also working to educate buyers, including outreach to the Culinary Institute of America to share information on virgin olive oil and oil from abroad that may be adulterated.

Mechanization, disease, and water

The program also looked at the following topics:

Mechanization of pruning and harvesting

Louise Ferguson, UC Davis Extension specialist in plant science, said some significant progress has been made in coming up with machine-harvested fruit that is not distinguishable from hand harvested olives.

Ferguson said sensory panels and consumer evaluations were used to judge differences between machine and hand harvested olives.

And machine harvesting does not appear to damage trees greatly, particularly if they are pruned properly. Researchers continue to modify harvesters that either shake the trunks of trees or operate in canopies.

Ferguson said mechanical harvesters must be at 80 percent efficient to equal the cost of hand harvest. At this point, she said, the efficiency rate in shakers is 64 percent; it’s 68 percent for canopy harvesters.

Ferguson said a study showed mechanical pruning did not reduce yield. She said thinning should be done annually.

Olive knot and verticillium management

Elizabeth Fichtner, UC farm advisor for Tulare County, said olive knot can affect fruit flavor. It girdles stems, branches and trunks and results from bacteria that enter through scars in wood, commonly during spring rains.

Fichtner said it can be exacerbated by pruning or harvesting before or during rain, and mechanized harvesting can leave “infection ports.” A post-harvest copper-based treatment in late fall helps combat the disease, but it is developing copper resistance.

Plants coated with a latex polymer have reduced sensitivity to freeze-injury, researchers have found. And several table and oil olive growers in Tulare, Kings, and Fresno Counties are using a latex polymer product for frost protection. Some growers combine the latex polymer with copper in a tank mix to enhance olive knot control.

As for verticillium wilt, sometimes a legacy of old cotton fields, Fichtner said the best way to avoid that soil borne fungus is to not plant olive trees in infected soil.

Use of olive mill waste water for nutrition and management of olive diseases

Ali Rhouma is studying those topics in the African nation of Tunisia at the Laboratory for the Improvement and Protection of Olive Genetic Resources.

He pointed out that Tunisia is either second or third each year in the world export of olives.

Rhouma said research showed waste water from olive oil extraction did not change the Ph levels of soil and that it added organic matter and potassium. He is studying its use on various diseases in olives including root rot, olive knot, leaf spot and branch dieback.

Insect pest management in olives

The olive fruit fly is developing some resistance to the insecticide Spinosad, said Marshall Johnson, an integrated pest management specialist and entomologist with the Kearney Ag Center.

That could mean growers will need to resort to other approaches such as mass trapping, improved orchard sanitation and biocontrols, Johnson said.

Johnson said dense, unpruned canopies are a haven for another pest, black scale. That problem is often compounded by ants that disrupt parasites. And the olive fruit fly may feed on honeydew produced by the scale.

“It’s a double whammy,” Johnson said. “The black scale sucks the vigor from the tree and helps support the olive fruit fly.”

Density in the canopy of olives is also a haven for the olive psyillid, notably in Southern California. But Johnson said that pest is unlikely to thrive in the hotter temperature of the San Joaquin Valley.