Nine fungicides are awaiting EPA Section 18 registration for use on soybeans to help combat soybean rust, according to Marty Draper, South Dakota State University extension plant pathologist.

Currently, only two chemistries are registered for use on soybeans to fight soybean rust — azoxystrobin (Quadris from Syngenta Crop Protection) and chlorothalonil (Bravo WeatherStick, Echo 720 and others).

“That's not going to be enough to handle soybean rust if we have to address it,” Draper says. “The Section 18 registration is based on the concern that, with 148 million acres of soybeans in the U.S., if you treated with a low rate of Quadris you'd need nearly 7 million gallons of product just for one application.”

EPA is being asked to register four triazole chemistries, one strobilurin and two combination products. The triazoles include: 1) propiconazole — Tilt from Syngenta Crop Protection, PropiMax EC from Dow AgroSciences and Bumper from Makhteshim-Agan of North America; 2) tebuconazole — Folicur from Bayer CropSciences; 3) myclobutanil — Laredo EW from Dow; and 4) tetraconazole — Eminent from Sipcam Agro USA. The strobilurin is pyraclostrobin, or Headline, made by BASF. The two combinations are trifloxystrobin plus propiconazole, or Stratego, made by Bayer; and pyraclostrobin plus boscalid, or Pristine, manufactured by BASF. Approval is expected by mid-February.

How To Treat Soybean Rust

Preventative — If disease is expected but not yet present
First Application Second (if needed) Third (if needed)
Azoxystrobin or pyraclostrobin Section 18 triazole Chlorothalonil
Section 18 combination product* Chlorothalonil or Section 18 triazole
Azoxystrobin or pyraclostrobin Section 18 triazole
Azoxystrobin or pyraclostrobin Section 18 triazole Chlorothalonil or Section 18 triazole
Curative — If disease is established on site
First Application Second (if needed) Third (if needed)
Section 18 triazole Minimal rust — azoxystrobin Chlorothalonil
Severe rust — Section 18 triazole
*trifloxystrobin + propiconazole or pyraclostrobin + boscalid
SOURCE: MARTY DRAPER, SOUTH DAKOTA STATE UNIVERSITY