California Agriculture

California’s olive oil industry has evolved from primarily a salvage operation of the table olive industry to a producer of world-class, premium, extra-virgin olive oil. In 1997, UC Cooperative Extension started the first California olive oil taste panel, which was officially recognized by the International Olive Council in 2001. Specific protocols were used to screen potential panelists and train them to identify defects and positive characteristics, identical to 43 other world taste panels. The UCCE panel helped the California Olive Oil Council develop a seal certification program using sensory analysis. Certification provides consumers with assurance that labeled oils are free of defects and warrant the “extra virgin” grade. Sensory evaluation using a unique UCCE profile sheet provides complete and detailed information about specific positive flavor characteristics of olive cultivars grown in California. The UCCE sensory panel has also contributed to a better understanding of the qualities of California olive oil and advancement of the industry by participating in research on pest management, cultural practices and processing.

The olive fruit fly was first detected in Los Angeles in 1998 and in all the olive-growing regions of California soon after. Following its initial detection, UC researchers and Cooperative Extension farm advisors, county agricultural commissioners and the California Department of Food and Agriculture Pest Detection and Emergency Project established a statewide monitoring program to determine the extent of the olive fruit fly’s occurrence, track its seasonal biology and evaluate monitoring tools. Fly populations and infestations can reach high levels throughout California but tend to be lower in the San Joaquin Valley. Trap captures typically exhibit a bimodal distribution with peaks in the spring and fall. Olive infestation is related to fly densities, climate and fruit size. Gravid, mated females vary in density throughout the year but are present at some level year-round. The data is being used to develop models that will better predict when the adults are active and olives are at risk.

The widespread and rapid establishment of the olive fruit fly in California required immediate changes in integrated pest management (IPM) programs for olives. After finding that resident natural enemies did not provide adequate control, researchers began a worldwide search for parasitoids, with exploration in the Republic of South Africa, Namibia, India, China and other countries. Parasitoids were shipped to California, and most were studied in quarantine to determine the best species for release. Two parasitoid species — Psyttalia lounsburyi and Psyttalia humilis — are now being released throughout the state’s olive-growing regions, and researchers are studying their effectiveness.

Olive fruit fly commonly infests olives in California’s Central Valley. Field studies indicate that trap counts for olive fruit fly adults in pesticide-free sites decrease in mid- and late summer and then rebound from September to November. Part of this decline is associated with heat stress that the flies experience in mid-July and August. Studies have shown that adult flies will die within a few days if they cannot access adequate amounts of water and carbohydrates. Flight ability is dramatically reduced when resources are unavailable. Olive fruit fly adults may use black scale honeydew as a carbohydrate source to help them survive hot periods. Heat also affects the fly’s reproduction and immature stages within olive fruit. Geographic information system (GIS) maps may be useful for predicting the risk of olive fruit fly infestation.

Traditional olive oil production is limited by its high cost, mainly due to labor expenses for harvesting and pruning. A new olive planting system based on hedgerows and harvesting machines could decrease production costs while maintaining high quality. To improve the efficiency of the continuous-straddle mechanical harvesters, vigor must be managed to limit tree size. However, few cultivars are adapted to this system. Selections from three cultivars are typically used in these super-high-density orchards. We field-tested ‘Arbequina i-18’, ‘Arbosana i-43’ and ‘Koroneiki i-38’ in an irrigated, super-high-density planting system in Catalonia (northeast Spain). We present a review of 6 years of horticultural data and summarize sensory characteristics and other properties of the resulting olive oils.

Many commodities depend on preplant soil fumigation for pest control to achieve healthy crops and profitable yields. Under California regulations, minimizing emissions is essential to maintain the practical use of soil fumigants, and more stringent regulations are likely in the future. The phase-out of methyl bromide as a broad-spectrum soil fumigant has created formidable challenges. Most alternatives registered today are regulated as volatile organic compounds because of their toxicity and mobile nature. We review research on methods for minimizing emissions from soil fumigation, including the effectiveness of their emission reductions, impacts on pest control and cost. Low-permeability plastic mulches are highly effective but are generally affordable only in high-value cash crops such as strawberry. Crops with low profit margins such as stone-fruit orchards may require lower-cost methods such as water treatment or target-area fumigation.