Almond experts draw from experience to provide grower tips

12/09/2011 02:19:00 PM
Vicky Boyd

Back in the 1980s, producing 2,000 pounds of nut meats per acre was a dream for California's almond growers.

Today, the state's almond growers average about 2,600 pounds of nut meats per acre and harvesting 4,000 pounds per acre isn't unheard of.

With the increase in production have come cultural changes and challenges.

A panel of three University of California experts, who collectively have nearly 100 years of experience, drew from their experiences and provided guidance for the future at the recent Almond Conference in Modesto.

Pest control, for example, has evolved.

In 1978, naval orangeworms caused an average of 8.8 percent defects. During the 2011 season, they caused a record low 0.68 percent.

Walt Bentley, an integrated pest management entomologist based at the Kearney Agricultural Center, attributed much of the decrease to winter sanitation.

Throughout the years, farm advisers and university experts have preached that removing mummy nuts during the winter, with no more than 2 per tree remaining, helped reduce overwintering NOW populations.

"When we started this, I didn't think we could get down to two," Bentley says, adding that Paramount Farms has a threshold of just 0.3 mummy per tree.

Although that means having a crew reshake or pole trees after harvest, it's well worth the effort, he says.

Recent research has tied Aspergillus flavus, the organism that causes the potential carcinogen, aflatoxin, to naval orangeworms.

The European Union has zero tolerance for aflatoxin and will reject contaminated shipments.

So the better job a grower can do to control NOW, the less chance he or she has of aflatoxin contaminating the crop.

Not only are naval orangeworms a pest of almonds, but they also attach pistachios and walnuts.

With the state's more than 1 million acre tree nuts, growers should think more about area-wide than individual pest control, Bentley says.

"What it does is you are creating your own landscape," he says. "It's not just the density but the nearly of your orchard to other nut crops that have the same pest problems."

Larger production=larger problems

John Edstrom, a UC Cooperative Extension farm advisor who just retired from Colusa County, called the industry's transformation over the years "truly remarkable."

He has seen the adoption of microsprinklers, high-density plantings with trees as close as 15 feet by 22 feet and orchards planted in some "pretty wild areas."

Growers now are pushing tree to come into production sooner with higher irrigation and fertilizer rates.

Three decades ago, growers never dreamed of harvesting a crop from a third-leaf tree, Edstrom says. Now they're seeing much higher production from third- four- and fifth-leaf trees.

Growers also have followed Edstrom's trials that showed lightly pruned trees yielded significantly more than heavily pruned trees.

But not all of these practices fit every planting situation, and Edstrom says growers may run into increased disease pressure from high vigor trees with dense canopies.

Alternaria, which never was a problem with wider tree spacings, now causes early leaf defoliaton if growers don't stay on top of the disease with fungicides.

Microsprinklers, coupled with a dense canopy, create the perfect microclimate for the fungal disease.

Hull rot, which is associated with higher nitrogen levels, also is becoming more of a problem, Edstrom says.

Mario Viveros, a farm adviser emeritus from Kern County, says hull rot is tied into higher yields, which delay overall crop maturity.

"The more we delay hull split, the more we are opening ourselves up to hull rot," he says. "There are trade-offs that we have to consider with yield increase."

In addition, growers are applying more fungicides because of increased disease pressures, whether from alternatia, hull rot or a host of others.

"I know of a couple of growers who put on seven fungicides sprays—that's getting up there," Edstrom says.

With an average cost of $50 per acre, including materials and application, those growers spent $350 per acre on disease control alone during 2011, he says

"Those high-input production systems produce earlier and have ultra-high yields, but often result in more problems and more costs," Edstrom says. "Especially in high fertility soils, you have to be careful where you apply these practices."

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