As public awareness of pesticide applications grows, so do the complaints associated with odors from agricultural practices. A recent Spray Safe event in Modesto, Calif., hosted by the Stanislaus County Farm Bureau, highlighted the issue of pesticide drift and its implications for growers. Spray drift, as defined during the session, is the airborne movement of pesticides away from the intended target area during or shortly after application, excluding post-application movement from volatilization, evaporation or soil erosion.

When investigating drift complaints, inspectors focus on several key factors and closely examine weather conditions, including wind speed, direction, temperature and other environmental factors at the time of application. Residue evidence is another critical aspect, with inspectors collecting samples from surrounding areas, such as swabs from surfaces and foliage samples, to determine if pesticide drift occurred. They also assess applicator decisions to evaluate whether “due care” was exercised, a standard requiring reasonable precautions like those of a competent professional in the same field.

Stanislaus County Deputy Agricultural Commissioner Judith Arroyo, who oversees the Pesticide Use Enforcement program, emphasized the importance of accurate sampling to provide physical evidence of pesticide presence and assess the degree of exposure.

“Our goal is to prove or disprove violations and guide mitigation strategies,” she said.

Arroyo explained sampling techniques can include surface swabs, residue collection and, in some cases, air and water samples, depending on the specific circumstances of the incident. When asked about the primary indicators investigated in a drift case, Arroyo said inspectors review weather reports, contact applicators about field conditions during the application and collect samples to assess whether drift occurred.

“It’s about understanding all factors and gathering evidence,” she said.

Odor Complaints and Drift Misunderstandings 

An emerging issue discussed at the event was the classification of odor complaints as drift incidents involving products like Zeal MVP and Goal 2XL. Chris Simas, territory sales manager at Valent USA, explained how Zeal MVP has been an effective tool against pests like spider mites, but it emits a noticeable smell during or after application.

“The odor isn’t pleasant, but it’s due to solvents that make the product more effective,” Simas said.

He encourages growers to communicate with neighbors before applying pesticides to reduce misunderstandings and foster better relationships.

“We want to encourage better conversations with your rural neighbors,” Simas said. “Tell them what’s going to happen so they can close their windows that night, and it’ll all be gone in a day or so.” 

Stanislaus County Agricultural Commissioner Linda Pinfold addressed the growing challenge of odor-related complaints, which she said often stem not from the active ingredients but from their inactive ingredients.

“It has distillate that vaporizes, that’s creating the smell, and that’s what people smell,” she said.

While these smells are not indicative of an actual exposure or hazard, Pinfold said, they can still provoke strong reactions. 

“People really react, and it’s the same kind of thing in many cases, like people feel ill just smelling people’s aftershave or perfume,” she said. “It can be something as simple as somebody smells it, and now they feel nauseous, and so now they’re complaining about it.”

Pinfold said while odor itself is not technically drift, ag commissioners are still required to investigate each complaint. That has kept her office busy in recent years, with the number of investigations and related complaints increasing between 2019 and 2023 by 122%.

Like Simas, Pinfold urges growers to consider their surroundings carefully, especially in areas with an agricultural-urban interface, and to communicate, particularly if they know they might have a difficult neighbor.

“If I was a grower and I know I have a challenging neighbor who may complain about this, I would probably give them a heads up, and I might even let my ag commissioner know if I think there’s a chance of hearing from them because of what I need to apply,” she said. “Open communication and proactive mitigation can prevent problems before they arise.”

Providing context can also help ease concerns, she said.

“It truly is that ounce of prevention to say, ‘Hey, we’re going to be doing this. This is an herbicide. You are going to likely smell it, but just because you smell it doesn’t mean it’s a hazard to you. You’re not getting exposure,’” Pinfold said.

Practical Steps for Drift and Odor Mitigation 

To mitigate the impacts of drift and odor, presenters at the Spray Safe event shared several practical steps, stressing the importance of timing pesticide applications during calm weather, early mornings or at night to minimize drift. Simas also noted there are some adjuvants that help with the odor and you should consult your PCA for those options.

He also reiterated the importance of maintaining open communication with neighbors about spraying schedules to alleviate concerns and help avoid complaints. 

“Odor is not drift,” Simas said. “If odor was drift, every dairyman in the county would have problems. When you pump gasoline, you smell gasoline, but it’s not drift.” 

Arroyo noted the role of sample collection in investigating drift claims, explaining the samples serve as critical evidence to determine the presence of pesticides, assess the extent of exposure and evaluate whether any violations occurred. 

“We want to understand what happened and whether due care was exercised,” she said.

Arroyo referred residents seeking more information on pesticide-related complaints to California Department of Pesticide Regulation’s Community Guide to Recognizing and Reporting Pesticide Problems, which outlines the steps taken during investigations and provides clear guidance on how to address pesticide emergencies or concerns.

Keeping Growers Ahead of the Curve

Stanislaus County Farm Bureau’s Spray Safe event has been held annually for almost two decades. Anna Genasci, the organization’s communication and education director, currently runs the program, which she said has had to evolve over the years to adapt to the ever-changing landscape of California’s strict pesticide regulations. The event is a collaboration between a committee and local regulatory bodies, including the agricultural commissioner’s office, which helps ensure the program reflects current concerns and changes in local practices and regulations.

Genasci said one of the most significant frustrations she sees farmers face is the constant evolution of regulations.

“The heartache is the goalpost keeps moving,” she said. “We bring growers into Spray Safe annually, and it seems like every year there is a new regulation to discuss.”

While growers work hard to adhere to the changes, she said the rapid pace of regulatory adjustments can be overwhelming.

“They adhere to the regulations and make those changes to improve practices, and then we change it up,” she said. “It’s one more thing to comply with.”

Some regulatory changes, Genasci explained, seem to be driven more by public sentiment than by science, a shift that complicates growers’ ability to navigate compliance and trust in the system. Decisions about pesticide use should be based on science rather than emotional reactions, she said.

“It does feel like now there are [regulatory] changes happening because of public interest rather than scientific findings, and that’s a real concern,” she said.