Push Back Powdery Mildew in Tomatoes

Starting early with a well-planned fungicide rotation is key to reliable control.

The return of drier spring growing conditions spells fungal disease pressure in tomatoes, including powdery mildew. The fungal species affecting tomatoes, Leveillula taurica, is found in most California tomato-growing areas, infecting weeds and crops in the solanaceous family. Spores are easily carried by wind, so any warm, windy day can set the disease in motion in your fields.

Staying ahead of powdery mildew infection with a preventive fungicide application is the best way to protect your crop, says Jeff Pacheco, DuPont Crop Protection technical sales agronomist. “Growers can’t afford to simply react to conditions in the fields. They need a season-long disease management game plan that includes a combination of fungicides applied in the proper rotation to manage powdery mildew outbreaks and minimize resistance development.”

Since this particular powdery mildew is difficult to control in tomatoes, growers should consider all options, he says. “Field trials in the San Joaquin Valley have demonstrated that DuPont™ Fontelis® fungicide delivers effective powdery mildew control as part of a rotational fungicide program.

Fontelis® offers key benefits:

  • Pre- and post-infection activity
  • Rapid penetration into plant tissue
  • Rainfast within 1 hour
  • Effective foliar disease control
  • Excellent crop safety
  • Compatible with fungicides, insecticides, adjuvants, liquid fertilizers and biological control products

Great rotational partner
Resistance management is an important element of an effective integrated pest control program, says Pacheco. “Choose fungicides as part of a season-long plan that rotates active ingredients.

Fontelis® offers flexibility for tomato disease-control plans, he says. “It’s the only single-active-ingredient FRAC Group 7 fungicide labeled for control of powdery mildew in tomatoes. Fontelis® can be used alone in a rotational program or it can be tank-mixed with other fungicides in rotational programs to improve powdery mildew efficacy. That makes it easier to design and implement a season-long rotational program with other powdery mildew fungicides that have different modes of action.”

No more than two sequential applications of Fontelis® should be made to a crop before switching to a fungicide with a different mode of action, he adds.

Effective black mold control
A disease more common in late-season processing tomato crops, black mold (Alternaria alternata) can devastate quality and marketability of ripening fruit. Most commonly found from San Joaquin County northward, black mold can also be a problem in the Central and Southern San Joaquin valleys when conditions are right. Black mold spores need three to five hours of wet conditions to germinate, then infect fruit by directly penetrating tomato skins or colonizing wounds, including sunburned areas. The disease can heavily damage the crop with black lesions within just four to five days.

A preventive fungicide application is the best defense against black mold and other late-season diseases. “Fontelis® has strong residual, preventive and curative properties to provide reliable control of diseases, including black mold and powdery mildew,” says Pacheco.


Always read and follow all label directions and precautions for use.
DuPont™ Fontelis® fungicide is not registered in all states. Contact your DuPont representative for details and availability in your state.
Unless indicated, trademarks with ®, ™ or sm are trademarks of DuPont or affiliates. © 2017 DuPont
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