From advice on ways to clear pomegranates for the most lucrative export markets for the United States to pointers on how to combat the worst insect pests, growers in the central San Joaquin Valley recently were provided with a trove of advice.

They were told of precautions they can take for export of the fruit, along with tips on how to combat diseases that could sour their markets in the United States and abroad.

The advice came during a pomegranate workshop at the Kearney Agricultural Research and Extension Center in Parlier, Calif.

The session opened with a talk from Jim Adaskaveg, a professor of plant pathology with the University of California at Riverside, who talked of the importance of complying with import protocols set by lucrative markets that include the Republic of Korea.

He said gray mold posed the greatest threat to sales in that market, and in 2000-2001 there were crop losses of up to 50 percent because of it. That percentage has been cut considerably due to actions taken by the industry since then.

Today, the biggest challenges come from “heart rot,” diseases that may go undetected initially. Because of those challenges, Paramount Farming Co. has stepped up to fund research.

Adaskaveg said gray mold remains a major problem for Korean importers. It results from flower parts being infected at bloom time. When it comes to pomegranates going into South Korea, two postharvest decays are regulated under quarantine: Alternaria “black heart disease” and dry fruit rot.
For exports to Korea, Adaskaveg said, growers must register orchards and packinghouses with the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service. Field requirements include removal of old branches and fruit; training of pickers, graders and others in identification of Alternaria decay; and inspection of 2 percent of each consignment before shipment.

The bottom line, Adaskaveg said, is that “black heart” cannot be managed by postharvest treatments for the fungi that cause the decay, Aspergillus niger and Alternaria. He said black heart infestation is often not visible from simply looking at the fruit, but infested fruit often weighs less than healthy fruit.

Chlorine washes help lessen the risk of damage from gray mold and penicillium decays, he said. along with removal of contaminated fruit  and treatment with a postharvest fungicide like Scholar.

 

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Other speakers at the workshop included:

• Maxwell Norton, UC farm advisor in Merced County, who talked of the biology of pomegranate trees.

He noted they are native to Iran and India, like hot and dry summers and can be damaged by very cold temperatures. Norton said the trees are tolerant of saline soils and, although drought tolerant, they benefit from irrigation to produce better yields and larger fruit.

Applying “even moisture” may reduce splitting, Norton said, and researchers are looking at applying boron to counter splitting as well. But Norton cautioned that some soils, notably on the West Side of the San Joaquin Valley, may already be high in boron.

Norton said there is some experimentation with mechanical harvesting for juice. Among challenges is the fact that fruit ripens at various times, he said, meaning “it’s rare to get away with just one picking.”

Pomegranates are self-pollinating.

More details are available at http://ucanr.edu/sites/pomegranates.