Sulfur has never been more important to growers than today. It represents the cheapest and most reliable material to control powdery mildew at a time when grape prices are at historical lows.
However, if California grape growers do not practice good stewardship, they may lose the old reliable.
“Misuse of dusting sulfur by growers will cause growers to lose dusting sulfur,” Madera County UCCE farm advisor George Leavitt told growers at the series of grower meetings he and Fresno County Farm Advisor Steve Vasquez conducted this spring on managing powdery mildew.
“Air quality people are looking at any excuse they can to get rid of sulfur. We have to be our own best stewards,” Leavitt said.
According to Vasquez, ag commissioners are going to encourage growers to be good stewards by increasing fines for improper use, which unfortunately the two farm advisors say are still occurring too frequently.
Vasquez said the Fresno County Agricultural Commissioner's office can levy fines from $50 for minor infractions like failure to properly fill out use forms to up to $5,000 for such things as sending a sulfur dust cloud into a school or home.
Misuse will be treated this year more harshly than every before, Vasquez warned.
When sulfur complaints began to mount, the industry created a California Sulfur Task Force that worked to create voluntary guidelines to minimize drift and avoid mandatory regulations. These were put into a booklet developed by the Coalition for Urban/Rural Environmental Stewardship (CURES).
Critical wind speeds
Among the key issues is applying sulfur when wind speeds are from 2 to 10 miles per hours. Applying sulfur in high winds conditions obviously can cause drift, but putting on sulfur when winds are less than 2 miles per hour can be equally bad.
When speeds are less than 2 creates an inversion or dead calm conditions can occur where sulfur clouds can drift off target.
“Carry a little wind speed indicator and record the wind speed when you are dusting,” said Vasquez Failure to turn off sulfur dusters at row ends continues to be a problem, said Vasquez, who said growers will be fined this year for failure to disengage blowers or slowing engine RPM. Also, he has seen growers improperly dust outside rows adjacent to roads with both fans operating. “One fan is just blowing sulfur on to the road and into passing cars,” said the farm advisor.
“If you are applying sulfur next to Highway 99 or any main thoroughfare, don't use dusting sulfur,” said Leavitt. “If dusting sulfur drifts across a major road, you can bet people will be on their cell phones calling someone about pesticides drifting all over their cars,” said Leavitt. “Use wettable sulfur in vineyards next to busy roads if you use sulfur.”
Be a good neighbor, said Vasquez. Create a buffer zone between where the sulfur is being applied and schools and houses.
“Don't assume just because school is out that there will not be people at schools in the afternoon or evenings,” warned Vasquez.
“Sulfur is one of the cheapest products we have for powdery mildew control, and we don't want to lose it, especially now when the prices for grapes are so low many growers cannot afford some of the newer compounds,” said Vasquez.