Federal environmental regulators are pressing ahead with plans to cancel a fungicide used in Northwest orchards despite the USDA’s concerns about unintended consequences.

The USDA and several farm groups argued for less drastic restrictions on ziram, but the U.S. Environmental Protection Agency has said it won’t alter a proposed ban on most uses of the chemical.

“Because of the risks associated with the use of conventional ziram products, the agency is proposing to cancel all conventional uses,” the agency said in an updated review.

Ziram is currently registered for agricultural applications on such Northwest crops as apples, blueberries, cherries, grapes and hazelnuts.

In late 2021, the EPA initially announced its intention to prohibit conventional uses of ziram as part of a period review of the fungicide. Some non-agricultural antimicrobial uses may be allowed under the plan.

Though EPA received recommendations to minimize ziram’s dangers from USDA and several crop organizations, the agency has now said, “It did not change the previous risk picture and proposal.” However, it’s providing another opportunity to comment on the ban until July 1.

The USDA advised the agency to retain some allowable uses of ziram to avoid the “unfortunate, unintended and fundamentally preventable outcome” of resistance “burn-out” among newer fungicides.

“Beyond just economic impacts to growers, we urge EPA to also consider that eliminating multi-site protectant options from the agricultural fungicide toolbox would likely drive unintended consequences on usage of other fungicide active ingredients,” the USDA said.

It’s unfortunate the EPA hasn’t been persuaded to allow some limited use of ziram, which could help forestall fungal pathogens from developing an ability to withstand other chemicals, said Katie Murray, executive director of the Oregonians for Food and Shelter agribusiness group.

“Reducing what’s available in the toolbox will lead to over-reliance on what’s left,” Murray said. “It’s a critical tool not just because it’s highly effective but because of managing fungicide resistance.”

Some fungal diseases in tree fruit are already becoming tolerant to fungicides, but farmers can undermine that adaptation by rotating chemistries to kill resistant pathogens, she said. Newer fungicides are typically considered safer than older products like ziram, but if growers can’t switch up chemicals, these modern fungicides will likely lose efficacy more quickly.

The EPA has imposed mitigation measures that decrease usage of other pesticides without banning them entirely, so it’s disappointing the agency isn’t willing to take that step with ziram, Murray said. The benefits of preventing broader fungicide resistance would likely outweigh the risks posed by scaled-back spraying of the chemical.

Together with other looming restrictions, the ziram proposal represents a narrowing of the alternatives available to farmers, she said. “When you take this with all the pushes from EPA, the ability to produce a crop continues to be eroded.”

The EPA’s decision to cancel most uses of ziram is primarily based on the hazards faced by “occupational handlers” who spray the chemical, rather than public exposure through food and water. The agency determined the fungicide poses “unreasonable risks” of being inhaled by applicators, even if requirements for personal protection and other controls were strengthened.

The USDA urged the agency to consider “risk mitigation options” for continued use of ziram, as it’s one of several “cornerstone disease management tools” whose elimination would adversely impact agriculture.

“These fungicides are critical for the effective and continued management of fungicide resistance,” the USDA said.

By maintaining the “sporadic use of older, reliable tools” such as ziram, the EPA can “preserve the safe use and efficacy of newer, safer but also resistance-prone chemistries,” according to USDA. The use of ziram as a “backstop” is particularly important for crops “vulnerable to higher levels of precipitation and plant disease outbreak.”

“We suggest that a number of potential label mitigation options, including medium and coarser droplet size, lower application/boom heights, and prohibiting applications when wind speed exceeds 10 mph could significantly reduce drift estimates to an acceptable level,” the USDA said.

Concerns about fungicide efficacy have lately taken on added relevance for Oregon’s hazelnut industry due to a new variety of Eastern Filbert Blight that can infect trees bred to resist the disease.

However, chemicals still available to the industry should be able to ward against fungicide resistance even if ziram is prohibited, said Jay Pscheidt, plant pathology professor at Oregon State University.

A bigger worry is whether EPA’s action with ziram could foreshadow restrictions on chlorothalonil, on which hazelnut growers depend to control the blight, Pscheidt said.

“My concern is a more holistic picture with EPA,” he said. “What’s the other foot coming down with chlorothalonil going to be?”