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Warm winter challenges almond crop

It has been a welcome wet winter in California, but not a particularly cold one and this could prove challenging for almond producers.

Rainfall totals around New Year's were of frog strangler proportions and snow pack totals are well above normal. San Luis Reservoir in the Central San Joaquin Valley was brim full in mid-January, months before it is scheduled to receive snow pack runoff from Northern California via the state's massive water storage and collection system.

No one is complaining about the wetness, but there are concerns about low chilling hours. There is still time to make up for some of low hours for some deciduous trees, but time is running out for the state's 550,000 acres of almond orchards.

Buds for the 2006 crop are beginning to swell ahead of the traditional mid-February bloom start.

Growers and Pest Control Advisers (PCAs) normally have plenty of in-season almond bloom pollinating weather and bee pollination worries. However, these could be exasperated by a long, uneven bloom period due to a lack of chilling in the winter of 2005-06.

How to handle disease sprays in a staggered bloom was one of the first questions tossed at a panel of University of California experts at a recent tree and vine seminar sponsored by Bayer CropScience in Monterey, Calif.

Madera County, Calif., farm advisor Brent Holtz fielded it first. He emphasized treating for disease prevention with fungicides at full bloom.

“I would probably push back the normal first pink bud spray at 25 percent and spray later,” he said, explaining that Nonpareil is normally the first to bloom, but it is also more resistant to brown rot than Carmel and similar varieties.

By pushing back the first Nonpareil bloom fungicide spray, a grower could possibly capture so-called California varieties in full bloom. The more trees in bloom, the fewer fungicide spray passes necessary.

“We had low chilling hours in December and this could mean the trees will not break dormancy evenly. Instead of bloom lasting one or two weeks, it could last a month,” he said. This would leave the trees and their worth-its-weight-in-gold almond crop more susceptible to diseases. Crop set is everything with California almonds.

Madera can get 1,000 chilling hours per winter, but this year it was about half that by mid-January, said Holtz. Chilling hours are those between freezing and 45 degrees.

Unlike pistachios which need about 1,000 chilling hours, almonds can get by on about 300 to 400 to set a crop. However, low chill hours can affect when trees break dormancy.

“We have some time left to accumulate more chill hours for trees like pistachios, but the accumulation of chill hours for almonds is coming to a close pretty quickly with bloom at hand,” said Holtz.

Fortunately, almond growers have a full arsenal of fungicides to deal with any disease at bloom or season-long, according to Jim Adaskaveg, UC Riverside tree nut and fruit tree plant pathologist who was on the panel with Holtz.

“I am really excited about this era we are in of working with new fungicides. There has been no time I can recall in my career that has been remarkable as the past six years in the development of new products,” said Adaskaveg.

Two of the products he has been working with during that period are fungicides Scala and Gem from Bayer CropScience. Scala was registered in California in December and targets brown rot blossom blight, shot hole, botryosphaeria blight, scab and blossom and shoot blight. It will be widely available this spring.

Gem, which has gone into posting by California Department of Pesticide Regulation, should be fully registered in California in February. It controls anthracnose, a growing problem in California almonds, shot hole and scab. It also suppresses brown rot blossom blight. It also controls botryosphaeria panicle and shot blight, shot hole and alternaria late blight.

“The university has been involved for five or six years in research on these products, gathering data to carefully prepare ourselves for when these fungicides would be available,” said the plant pathologist.

‘Ready with data’

“We are ready with a lot of data for these products to come out of the gate smoking,” Adaskaveg told the PCAs at the meeting as he detailed several years of commercial trials comparing Scala and Gem to other fungicides.

“These new products from Bayer fit nicely into the California disease control program,” said the UC researcher.

The program in California involves first effective control of diseases in almonds, one of the most highly prized crops in the state with prices reaching $4 per pound to growers for 2005. Prices are not expected to come down very much in 2006, even with a big crop.

But just as importantly is the resistance management element of fungicide use. The bottom line is the more the merrier so growers can rotate modes of action and stave off any resistance.

There are now 10 classes of fungicides to control almond diseases. A decade ago there were probably fewer than a half dozen individual products. There are at least two commercial compounds in each fungicide class.

Rotating modes of action among products in those 10 classes will allow producers to continue to enjoy the fruits of the fungicides developed over the past six years for years to come by practicing resistance management, Adaskaveg mentioned.


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