This is a final research report from Hort Innovation’s historical archives. Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.

What was it all about?

In September 2010 a study tour group visited California to investigate dried grape production. The group was made up of mostly dried grape growers, two Dried Fruits Australia staff members and one processor/marketer.

The tour covered numerous visits and meetings with some of the major players in the California raisin industry, including producers, raisin processors/marketers, researchers (including USDA vine breeders) and others involved in irrigation management research. Other visits included dried tree fruits and prune processors and the California Table Grape Commission.

The study tour objectives included:

• On-farm visits – to observe and discuss best practice production management and the various Dried On the Vine (DOV) mechanical harvesting options being used to achieve high quality raisins. It was also an opportunity to better understand the biosecurity issues facing Californian viticulture due to serious pests and diseases such as Pierce’s disease.
• Raisin processor/marketers visits – to observe best practice processing using the latest available technologies to produce high quality end products. It was also an opportunity to assess the latest raisin market outlook and gain insight into US consumer trends.
• Research (vine breeding) – to discuss and review USDA raisin breeding programs and the potential for further imports into Australia. This matter was important, given Dried Fruits Australia’s impending involvement in commercialisation of two new varieties.
• Water management – to review and gain an understanding of the water management and response to reduced availability of water for irrigation purposes and need to cater for environmental water requirements.
• Californian raisin industry contacts to establish a range of new industry contacts to open up the Communication channels between the US and Australian industries, then maintain these relationships and ensure growers in both countries were better informed.

Some of the main observations by the study group included:

• The climate in the Centre Valley based around Fresno and Selma was reliable for drying with no rainfall during the harvest period of July to September and average maximum temperatures of 35.5°C (96°F) peaking at 43.3°C (110°F). This provided ideal conditions to dry fruit on paper trays on the ground
• The soil was deep sand, up to 49m (160ft) deep. In parts of the valley there was a compacted zone somewhere between 0.9–1.8m (3–6ft) deep which restricts vine root depth
• Vines were planted almost universally to 2.1m (7ft) vines spacings and where traditional hand harvesting was still the practice, were grown on a single wire trellis. As a result, most vines seemed more vigorous than those in Australia, but did not produce extra fruit. There appeared to be little attention to vigour balance and subsequent shading
• There was a large swing over to new varieties to replace Thompson Seedless, with a focus on either Fiesta or Selma Pete to take advantage of their earlier maturity and better production capability. In addition, longer drying periods for the new varieties gave growers the opportunity to adopt trellis drying, a practice that was relatively new to them.
• Despite the change to new varieties, the US still had relatively low consumption of about 0.6kg per capita compared to Australia’s 2kg per capita.
• About 6,000ac (2,424ha) of poorer vines were being removed each year due to replanting to higher returning crops such as almonds, walnuts and Clementine mandarins. As a result, there was a slow reduction of surplus fruit which saw the price of TS raisins slightly increase on the world market
• In terms of water and environment, Californian growers at the time had access to cheap reliable sources of water. Snow melt from the Sierra Nevada Mountains provided flood irrigation and replenishes the aquifer. Despite this, the water table was getting deeper beneath the soil, making it more difficult to pump for irrigation
• Another area of potential change could have been occupational health and safety – the study tour group saw little evidence of use of things such as ear plugs/muffs, eye protection and dust masks when on the farm and there were no cab tractors or cabs on machinery. This was vastly different to Australia and Europe where attention was given to protecting those that grow the crop as well as those that eat it.