Powdery mildew in sugar beet fields

Powdery mildew covers sugar beet leaves with a white powder that feeds on the plants.

Fungus thrives in sugar beet fields in hot, dry weather


Capital Press

BOISE -- Sugar beet farmers in Idaho's Treasure Valley are experiencing heavy pressure from a fungus that reduces yields and sugar content, having benefited from a relative reprieve from the disease during the previous two growing seasons.

Powdery mildew, which covers sugar beet leaves with a white powder that feeds on the plants, arrived this summer about two weeks earlier than it did during the summers of 2010 and 2011, said Clark Millard, Amalgamated Sugar Co.'s district agricultural manager in Treasure Valley.

The fungus is spreading east and has already surfaced in fields in the Magic Valley near Filer, Idaho, according to an email alert recently sent to growers.

Millard said it was first spotted in Nyssa, Ore., on July 19.

"It was fairly well established, so it had been there for a number of days," Millard said.

Millard said the fungus likes dry, hot weather. He said it also tends to thrive more in surface-irrigated fields than under sprinkler irrigation, possibly because sprinklers wash off the mildew and offer less humidity.

He advised growers to be mindful of the threat in order to plan fungicide programs, making applications every one to two weeks. In addition to fungicides, elemental sulfur -- either alone or in a tank mix -- is effective against powdery mildew, he said.

"Usually it affects every acre in Treasure Valley to the point where we have to treat," Millard said.

In the Magic Valley, certain growers can sometimes get away with not treating for the fungus, Millard said.

Duane Grant, chairman of the board of Snake River Sugar Co., said farmers in his region occasionally have to treat their sugar beets for powdery mildew.

"It ramps up from Twin Falls west. To the east, it'll be an issue in some years, but it's generally not a real serious production issue for us," Grant said.

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