Research shows Valent’s Quash fungicide appears to boost spud yields

Crop scientists at Miller Research say they’ve seen a significant yield boost in potatoes treated with Valent’s Quash fungicide.

Jeff Miller, the research company’s president and CEO, said the boost has been observed in all 14 research trials involving Quash that he’s conducted during the past four growing seasons.

Miller believes it is caused by a physiological change in potato plants, which tend to be shorter and greener when treated with Quash, rather than due to improved disease control. The product is a broad-spectrum triazole fungicide containing metconazole.

“It varies from year to year, but you could probably get 30 to 40 sacks (of potatoes) more,” Miller said, adding Quash had no impact on tuber size or quality.

He said a boost of just a few sacks would more than cover the added expense of using Quash. Miller said a few of his trials were funded by Valent, initially to test the product’s efficacy for diseases it’s labeled to control in potatoes, including white mold and early blight.

Valent’s competitor, BASF, funded additional Quash trials, hoping to find good products to mix with its flagship fungicide Endura. The Idaho Potato Commission also funded some of the Quash trials.

Miller said a single treatment with Quash near the row-closure stage seems to be sufficient to produce the yield boost. Though Miller advises against using Quash as a stand-alone treatment for white mold and early blight — noting testing shows it’s less effective than top-line products such as Endura and Luna Tranquility, by Bayer Crop Science — he sees great potential to mix Quash with other fungicides to delay the onset of resistance. Miller said it’s been a hard sell to get growers to use “multiple modes of action,” due to the added expense.

“If anything, the disease control wasn’t quite as good with Quash, yet yield-wise it’s performing better,” Miller said.

Though Quash is labeled for potato use in the U.S., Northwest growers are avoiding it until maximum residue limits for the product are set in foreign markets, removing the threat of export challenges, Miller said.
“The thinking is it could come at any time, or we could go a whole season without using it under the worst-case scenario,” Miller said.

Miller said some chemical companies have made claims that strobilurin fungicides produce a similar physiological yield boost in spuds by affecting enzymes responsible for producing ethylene, a chemical that causes plant senenscence. Miller said he’s never noticed any yield bump from strobilurin on par with Quash. Once MRL issues are addressed, he plans to encourage growers to plant their test strips to see if they experience the same results.