California, USA: Postharvest pest management, nutrition, and irrigation critical for next year’s almond season

Western Farm Press Daily

Advice from two authorities on growing almonds in California – Jhalendra Rijal, University of California (UC) area integrated pest management advisor for the northern San Joaquin Valley, and David Doll, UC Cooperative Extension pomology farm advisor in Merced County.

The hay may be in the barn and the almonds at the processor, in storage, or on the shelf. But that doesn’t mean the farming stops.

That’s the advice from two authorities on growing almonds in California – Jhalendra Rijal, University of California (UC) area integrated pest management advisor for the northern San Joaquin Valley, and David Doll, UC Cooperative Extension pomology farm advisor in Merced County.

Both men spoke at an almond post-harvest management field day in Los Banos, presented by UC and the San Joaquin Sustainable Farming Project.

Rijal said postharvest should start with a sample that “gives you the extent of damage by different insects.”

From there, growers and pest control advisors can draw on a trove of information on controlling those pests on the UC integrated pest management (IPM) website – www.ipm.ucdavis.edu/PMG/selectnewpest.almonds.html.

Rijal is hearing that Navel orangeworm, one of the most troublesome pests for the almond industry, is posing a considerable problem again this year with damage levels in some Valley orchards up to 10 percent to 12 percent.

To counter the pest, Rijal emphasizes orchard sanitation, removing mummies that may contain larvae by Feb. 1. He acknowledges it can be labor intensive, involving hand-pulling the mummies or shaking them out of trees.

Rijal said, “That’s the best option. They must be removed and destroyed.”

By March 15, he said mummies should be destroyed by flail mowing and shredding.

Rijal warns against applying broad spectrum pyrethroids during May since it can cause mites to flare. He says it’s best to use softer chemistry Bt products including Intrepid, Delegate, Entrust, Altacor, Proclaim, and Best.

He also advises softer materials for peach twig borer control.

Monitoring for the degree of any pest infestation was another emphasis of Rijal’s talk. He urged listeners to check the IPM website for guidelines on thresholds to determine the point at which spraying is in order.

For example, Rijal says it is important to monitor scale populations, checking 100 spurs randomly taken from 50 trees, and then basing treatment decisions on the percentage of infestation.

If sprays are needed, he recommends applying 100-200 gallons per acre and to remember that scales can be hidden and unlikely to be hit by sprays.

He said broad spectrum insecticides can cause less damage during the dormant season compared to the same insecticide used during the growing season.

When spraying, Rijal suggests calibrating sprayers and other equipment and use a sufficient volume of water. He says pay attention to weather and avoid rain or foggy conditions, minimize spray drifts by shutting the sprayer off while making turns, and mix or load pesticides in places away from bodies of water.

Those who attended the workshop shared with Rijal their concerns over the leaffooted bug, a pest that overwinters, particularly given recent mild winters, and “comes out earlier.”

Another concern is lower limb dieback, which is claiming lower portions of trees. He says the cause for the problem is unknown.

Doll discussed postharvest nutrition and irrigation, and the importance of determining whether a leaching program should be adopted to seek to remove salts from the root zone. Before doing this, he suggested that growers should conduct soil sampling to determine any potential issues with sodium, chloride, or boron.

“These salts are ‘imported’ onto the farm through fertilizers and soil amendments, with the largest amount coming through irrigation water,” Doll said.

The problem can be particularly acute as growers have turned increasingly to groundwater for irrigation.

Doll says several online videos explain the procedure for collecting a soil sample available at http://thealmonddoctor.com/2013/09/23/soil-sampling-videos/. He adds that leaching should be considered if sampled soil shows electrical conductivity exceeding 1.5.

“Try to do it before the rains arrive in late October or early November,” Doll said.

Winter rains can also help push the salt out of the root zone.

Doll says the postharvest period is not a time to skimp on irrigation.

“Get it on as soon as you can so the tree can pull it up while leaves are still on,” the pomologist said. “Fill the tank before the tree goes to sleep.”

Postharvest is a critical period of full bud development, he says, and it extends a month from harvest, a period when it is important to minimize stress.

It’s also an important time to apply nutrients, as much as 20 percent of the nutrition budget.

During dormancy, Doll says it’s especially important to replace potassium, a time when 50 percent to 75 percent of the potassium budget should be applied, depending on soil types and crop loads.

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