Published online: May 22, 2012 Fungicide
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AMERICAN FALLS, Idaho-J.R. Simplot, Co., and Lamb Weston have told potato growers in Idaho and the Columbia Basin that they won't accept potatoes treated with Luna Tranquility, a fungicide recently released by Bayer CropScience.

A Simplot spokesman said a maximum residue limit for the product hasn't been accepted by Japan, a buyer of Simplot processed products. Lamb Weston also restricted potatoes grown with Luna Tranquility, explaining in a statement to growers: "Unfortunately, Bayer does not have an MRL with the Pacific Rim countries. ... Please be aware we will not be able to accept potatoes with Luna fungicide applications."

The product, released Feb. 3 in the U.S., has been heralded by potato growers as an alternative to BASF's fungicide Endura, which has begun to lose effectiveness against early blight.

"It would have been a change-up, which is always good for us to change from a chemistry to another chemistry so we don't get resistance," said Klaren Koompin, an American Falls grower, describing the loss as inconvenient but not devastating. "The studies look extremely good."

Ritchey Toevs, a Simplot grower from Aberdeen, is disappointed he can't use "an interesting product for white mold and things like that.

"We were really excited about having it, so that was unfortunate. It was nice to have a new active ingredient," Toevs said.

Herb Young, fungicide product manager with Bayer, explained the EPA set the Luna MRL for the U.S. at 0.02 parts per million. In tests involving five Luna applications, the highest residue concentration on spuds was 0.016 parts per million.

Young said it takes about a year after approval of a U.S. label to get an MRL in Japan, which would be April of 2013 for Luna. Prior to setting an MRL, Japan temporarily utilizes a standard level for all products of 0.01 parts per million, well below the Luna test results.

Young said Bayer has delayed release of Luna Sensation, used for cherries, anticipating challenges with Japan's MRL, but he never anticipated there would be an issue with potatoes.

He said Luna Tranquility would typically be applied no more than twice in actual production. Furthermore, Japan, which buys 1.6 percent of the U.S. potato crop on average, accepts only processed U.S. potatoes. The combination of washing and peeling a potato reduces residue by 85 percent, Young said.

Young said Bayer representatives have been in contact with several growers, relaying the processors' concerns.

"It's been a dramatic affect in the regions where there are processed potatoes," Young said of Luna sales. "The need has been so significant because some other things aren't working and the efficacy is so high. It's a shame it's slowed it down this first year."

Luna Tranquility, typically first applied around when potato flowers drop, is a combination of two chemicals, controlling a broad spectrum of diseases such as white mold, early blight, brown spot and black dot. The Luna portion offers the next generation of SDHI fungicides.

Jeff Miller, who tests chemicals with Rupert-based Miller Research, recently spoke with officials from McCain Foods about the Luna issue. He said they're considering their options, and he expects them to announce a decision soon.

SOURCE: John O'Connell, Capital Press