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By Brad Carlson
Recurring powdery mildew appeared early; CLS has been intensifying in recent years.
Powdery mildew and Cercospora Leaf Spot have been found in some southern and eastern Idaho sugar beet fields. Capital Press File
The Pacific Northwest Pest Alert Network in late June notified sugar beet growers in southwest Idaho and eastern Oregon about powdery mildew, Cercospora Leaf Spot and the looper insect.Capital Press
The advisories did not worry Wendell Robinson, agricultural manager for grower-owned cooperative Amalgamated Sugar’s western region.
“At this point, everything is manageable and treatable,” he said.
Robinson said beet fields should remain healthy overall if growers stay aware of pest and disease threats, and know how to treat them.
A crop consultant with J.R. Simplot Co. found powdery mildew in fields near Adrian, Ore., and Parma, Idaho, a June 23 alert said. Staff with Amalgamated Sugar confirmed the finding.
The alert said several fungicides are available to treat powdery mildew, and that applications should be repeated every two to three weeks depending on the disease pressure and chemistry used. A network publication said the fungus — whose spores can blow in from plants that carried over from winter, including previously infected seed beets — causes small white patches on both leaf surfaces. Widespread in several Western states for more than 40 years, it is often treated with sulfur dust.
Powdery mildew is “more or less a recurring problem we are having in the Treasure Valley” of southwestern Idaho and eastern Oregon, said Amalgamated Sugar Plant Health Manager Oliver Neher.
“Most of the time we see it in early July and it moves from west to east, he said. “We are seeing it this year a little bit early.”
Neher does not expect powdery mildew to be more of a problem than usual. Timely application of fungicide makes it fairly easy to control, he said.
The network on June 25 advised beet growers to start scouting for CLS as temperatures rise, beet field rows start closing and irrigation stays intense. Favorable conditions for the fungus that causes CLS materialize when average nighttime temperatures exceed 60 degrees and humidity is 90 percent or higher for at least five hours, the alert said.
An increase in fungicide resistance makes proper chemistry rotation important in treating for CLS, the alert said. It recommended consulting with Amalgamated field staff.
Sugar beet growers can control CLS by applying fungicide in a timely manner and by not over-watering crops, Robinson said.
CLS was not a major problem in southern Idaho and eastern Oregon until four to five years ago, Neher said.
“We saw a shift in temperatures and irrigation methods,” he said. As more irrigators used sprinkler pivots and hand lines, the moisture part of the equation became more favorable for the fungus that causes CLS, he said.
Last year saw many very overcast days with high relative humidity. “We even saw CLS in furrow-irrigated fields, where it is not so common,” Neher said.
If this year’s wildfire season is active, smoke conditions could increase relative humidity and in turn keep conditions favorable for CLS as leaves stay moist longer, he said.
Also June 25, the network said Amalgamated Sugar reported that loopers, which are minor leaf-feeding pests controllable with biological or chemical means, were found in fields in the Caldwell, Idaho, area.
Robinson said the small, worm-like loopers often are controlled by applying an insecticide in conjunction with a fungicide.
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June 27, 2018 at 01:33PM