Sulfur drift draws attention Unless complaints of sulfur drift are curtailed, one of man's oldest and most widely-used ag chemicals could become a restricted pesticide in California.
Hopefully that will be averted with a set of best application practices for dusting sulfur, which accounted for about 65 million pounds, or nearly one-third of the 202.6 million pounds of pesticides used in the state in 1999.
In Fresno County, the top-ranked pesticide user among all 58 counties, with nearly 37 million pounds applied, almost one-half was dusting sulfur.
Primarily used as a fungicide against powdery mildew on grapes, it is also applied to protect processing tomatoes, sugar beets, and other crops from the disease. It is also a miticide.
The California Department of Pesticide Regulation has received enough complaints of drift to place continued, unrestricted use of sulfur in jeopardy.
In response to the drift concerns, DPR, agricultural commissioners, the Coalition for Urban/Rural Environmental Stewardship (CURES), and the California Sulfur Task Force, registrants of the material, compiled the best practices in a four-page brochure.
It is available through CURES (tel. 916/646-9951), chemical dealers, and ag commissioners. An English version is currently available, and a Spanish version is being prepared for the coming season.
Focusing on weather conditions, equipment, and timing, the practices are intended to eliminate or reduce as much as possible sulfur drift near sensitive areas such as schools and other densely populated sites.
Jerry Prieto, Fresno County agricultural commissioner, was involved in developing the practices. He says although sulfur is the least intrusive to the environment, humans, and non-target life forms, it has come under increasing attack, largely due to drift incidents.
Sensitivity reaction "Because it is thought of as a safe material, some applicators do not use the same caution and care in applying it as they would when applying other pesticides," he said, adding that the element can cause eye irrigation and breathing difficulty for those sensitive to it.
That's something the 50-year-old Prieto can relate to. He recalls as a boy complaining of itching eyes after applying sulfur as a miticide on cotton on his family's farm at Corcoran.
Prieto and his fellow ag commissioners began encouraging awareness of the practices last year. Fresno County held 30 continuing education classes aimed at preventing sulfur drift and will be stepping up the program this year.
"We will continue classes in 2001 as soon as the sulfur applying season starts," he said. "In addition, we will be conducting sulfur application inspections near sensitive sites to ensure that applicators are practicing best practices.
"The whole idea is we want to protect the use of sulfur. We are focusing on education to do it, so we can make the effort work for everyone."
Safe application techniques center on working with weather conditions, controlling spray deposition, familiarity with the application site, and knowledge of surrounding sensitive sites and hazards.
Chief among the guidelines is application only when winds are no more than 10 miles per hour.
Air temperatures during application are also critical. In some parts of the state, so-called "dead calm" conditions may mean an inversion layer has formed because air 20 to 100 feet above the ground is warmer than air below.
The warm layer blocks vertical air movement and tends to concentrate particles or spray droplet. Rather than dispersing, the concentrated material may move away from the treatment site.
"We are asking growers to consider using wettable sulfur formulations, because they do just as good a job as dust," he said.
Prieto concedes, however, that since sulfur blowers are so common, a shift to other sulfur formulations and equipment to apply them isn't likely to occur overnight.
Regardless of the type of equipment used, it should be suited to conditions of the treatment site. Rigs too big or too powerful can be a problem when making applications near sensitive areas.
Shut-off valves Shut-off capabilities are important in controlling drift. Some dusters can be fitted with manifold shut-off valves or have hydraulic shut-off systems to allow operations to make row-end turns without discharging dust onto sensitive sites. Slowing down rigs at the ends of rows can also reduce drift.
Buffer zones, defined as enough distance for dust or spray to settle within the treatment area, need to be observed where drift might contact people, animals, or structures. The size of the buffer depends, of course, on the equipment used, the weather, the material being applied, and the sensitivity of the adjoining areas.
Ideally, sulfur treatments should be made at night or during weekends near urban areas, schools, bus stops, and highways. If an application must be made on land bordering public roadways, it should be made when traffic is at a minimum.
"Folks tend to think, because they've used sulfur for so long without the handling restrictions of other materials, that somehow it isn't really a pesticide," Prieto said.
"We are emphasizing it is a pesticide and must be applied with the same precautions as other materials."