The Evolution of Olive Harvesting

Mechanical methods essential to industry survival

“For us, moving to mechanical harvesting of table olives is not optional. It’s something we have to do, or we’re going to lose the industry,” said Bill Krueger, echoing concerns expressed in other produce industries. Krueger, University of California Cooperative Extension farm adviser, has worked with California tree fruit with a strong emphasis on olives for more than 30 years. He is a member the research team at UC Davis that is developing a system to convert the table olive industry from hand harvesting to mechanical harvesting.

Increasing labor costs, declining labor availability and imports from countries where labor costs are a fraction of U.S. labor costs are affecting the competitiveness of California’s table olives as the global market expands. Currently, around 25,000 acres of table olives are planted in California, down from about 30,000 a decade ago. California currently supplies about 50 percent of the U.S. table olive and olive oil needs. Most of the olives are grown in the Central Valley, made up of the San Joaquin Valley and the Sacramento Valley.

Developing a system

Working closely with the California table olive industry, the team includes university researchers and manufacturers as they work toward developing a mechanical harvesting system. Growers understand the importance of developing a mechanical harvesting system. The California Olive Committee is funding research, and aa per-pound assessment is levied on production to help find answers to keep the table olive industry afloat as production costs continue to rise.

Dr. Louise Ferguson, UC Davis plant sciences department researcher, is project leader. “We expect to have a usable machine within three to five years,” Ferguson said. A usable harvester is but one component of a complex mechanical harvesting system, with orchards that are adaptable to mechanical harvesting essential.

This pattern of converting to mechanical harvesting has existed in agriculture throughout commercial crop production. Olives, unlike many commodity food products, have seen little change in harvesting methods through the years. With harvesting costs running in the range of 45 to 60 percent of production costs, statistics back up Krueger’s assessment of the importance of a conversion to mechanical harvesting.

A major obstacle to mechanical harvesting of table olives is that table olives are harvested when they are less physiologically mature. This lesser degree of ripeness means that the olives are not so easily removed from the tree as when they reach full ripeness. The development of abscission compounds to loosen the fruit and aid in mechanical harvesting is being explored. Dr. Jacqueline Burns, University of Florida, a research team member, noted that finding the right chemical mix is difficult. She has worked with the development of abscission products for citrus for 20 years, and although the process is complex, some success has been obtained with its use in the cherry industry.

Olive Harvesting
Mechanically harvested table olives show varying degrees of maturity.

Mechanical harvesting in UC Davis trial plantings and commercial orchards was planned for this fall, when a canopy shaker was to be evaluated. Evaluating the efficiency of harvesters is a significant portion of developing the mechanized harvesting system, and both trunk and canopy shakers have been evaluated. Ferguson noted that while university researchers develop technology, the next step of actual harvester machine development and fabrication of a self-propelled unit with a catch and delivery system will be undertaken by manufacturers.

Ferguson cited the industrywide cooperation in California in developing the components that will make up a mechanical harvesting system. “Growers understand the need for mechanical harvesting,” she said. Additionally, she cited the benefits of international cooperation. Dr. Sergio Castro-Garcia, University of Cordoba, Spain, is a contributing member of the research team, and Ferguson is now on sabbatical in Spain studying potential methods that can be adapted to California.

“California is looking for diversity in produce, and olives offer a good option,” Ferguson said. “They can grow on less-fertile, well-drained soil.”

California olive oil

Olive Harvesting
Mechanically harvested table olives are inspected.

California’s entry into the olive oil industry has added an additional factor to the mix. With major investment coming into California about 10 years ago for the development of an olive oil industry, extensive plantings of olives for producing olive oil have been established. Nurstech, Inc., Gridley, Calif., ( is the major supplier of olive trees and rootstock. About 25,000 acres of olive oil groves now exist, paralleling the current acreage of table olive groves. These olive oil groves were initially established for mechanical harvesting. Krueger noted that while these olives are already mechanically harvested, the added acreage might encourage the registering of products needed by the table olive industry. Manufacturers are more likely to develop and register products for specific uses when a larger market exists, and the olive oil industry effectively doubles California’s current olive acreage.

California Olive Ranch is the state’s largest producer and contracts with numerous olive growers. Carriere Family Farms is among the contract growers, and grows about 450,000 olive trees on more than 800 acres that include Olive Glen Orchards in Artois. Arbequina, Arbosana, and Koroneiki olives are produced for oil.

Matt Lohse, who is responsible for farming operations at Olive Glen Orchards, cited two primary challenges to the olive oil industry: “Learning how to maximize our yields by taking ideas from throughout the olive industry is one of our major challenges. A second challenge is the learning curve in operating the mechanical harvesters. We started using a prototype five years ago, and we’re now using a fourth-generation revision of that machine, a Gregoire olive harvester manufactured in France.” Although California oil olives were harvested using modified grape harvesters for the first few years, several olive harvester models now exist. Lohse noted the importance of properly pruning trees in the mechanical harvesting system for efficient harvesting.

Olive oil trees provide model

“The olive oil industry that has developed is an excellent model.” Ferguson said. “We found that developing a harvester to work with existing tree shapes was the wrong approach. The trees need to be adapted to work with mechanical harvesters.” Olive trees for olive oil production are planted in a super high-density pattern and pruned to a hedgerow design for efficient access by the harvester.

While new table olive plantings can be designed for mechanical harvesting access, changing orchards over will take decades, Ferguson said. In the meantime, existing trees must be modified so the olives are accessible to the harvester head. The tree height must be adapted to the harvester, and the tree trained into a hedgerow that presents a flat fruiting wall to the harvester. Additionally, large wood must be removed from the trees, since large wood will not allow the harvester head to function and will result in tree damage.

Olive Harvesting
Harvesting olives used to make olive oil in Glenn County, Calif.

Planting patterns for future orchards must accommodate mechanical harvesting. Ferguson noted that potentially acceptable high-density planting patterns include trees planted 10 feet apart with 16 feet between rows or 12 feet apart with 18 feet between rows. UC Davis research includes various trials of mechanical pruning under way at Rocky Hill Ranch in Tulare County and experimental plantings established at the Nickels Soil Laboratory in Colusa County.

Challenges to competitiveness

While increasing labor costs and scarcity of labor are significant grower concerns, and weather is always a major and unpredictable challenge, growers face another issue that affects their competitiveness. Foreign subsidies are further spurring the need for mechanical harvesting to reduce production costs.

Dennis Burreson and his three sons grow Manzanillo and Sevillano table olives on 500 acres in Orland, Calif. Burreson is the chairman of the California Olive Committee research committee and supports the move to mechanical harvesting. His table olive operation includes about 100 acres planted with an eye to mechanical harvesting, which is to be done this fall. The plantings are on trellises 12 feet apart with 18 feet between the rows.

Along with rising production costs, Burreson is also concerned about the U.S. policy of providing assistance to countries that export olives to the U.S., competing with California olives. He cited the Millennium Challenge Corp., a foreign aid agency created by Congress in 2004 that provides grants to help developing countries. He sees olives coming into the U.S. from countries with subsidized production or that receive U.S. assistance for olive production as a negative factor in the competitiveness of California olive producers. About $320 million is promised to Morocco in a Fruit Tree Productivity Project, and 80 percent of that money is going to olives.

While California is the top-producing agricultural state, more than 90 percent of the state’s crops, including olives, are not eligible for federal subsidies. Burreson noted that California could return to its higher acreage and supply 100 percent of the U.S. market table olives and olive oil if acceptable profit margins can be attained. Supporting the development of a mechanical harvesting system is one step growers are taking to help assure the survival of the industry.

Encouraging progress

Any harvesting system, whether manual or mechanical, must be able to harvest fruit with minimal damage. A trained sensory panel that recently evaluated attributes of harvested fruit including flavor, flesh texture and composition, found no difference in manually and mechanically harvested olives. A consumer panel evaluation in a more general manner of liking or not liking and citing specifics was also unable to differentiate between manually and mechanically harvested olives.

Throughout the California table olive industry, growers share Krueger’s assessment that developing a mechanical harvesting system is not just an option; it is essential for the industry to survive.

Nancy Riggs is a freelance writer. She resides in Mount Zion, Ill.