Sunflower Rust

North Dakota, South Dakota, and Minnesota account for two-thirds of U.S. acreage of commercial sunflowers. 1.8 million acres of sunflowers produce an annual crop of nearly 2.8 billion pounds valued at $700 million. This valuable crop was recently threatened by a plant pathogen.

“Since 2008, sunflower rust has been a huge issue across the Northern Plains, increasing every year in severity and incidence.

The good news is that research trials conducted at North Dakota State University locations over the past two years demonstrate fungicides do work and in most cases, only one application of fungicide applied at the right time gives effective control .

“About three years ago, rust became an increasingly big issue,” said Sam Markell, NDSU plant pathologist, at the National Sunflower Association’s annual summer seminar in Bismarck. “When it comes really early, it causes a lot of yield loss.”

And that is precisely what began happening.

Previous to 2007, rust was typically found in late July and early August when it is less likely to cause an epidemic. But an NDSU Extension agent found rust in the aecia stage (which indicated the rust pathogen had completed its sexual cycle) three years ago in mid-June, which was very rare, Markell said.

“This may have been a result of favorable environment or it could be that a resistant sunflower was no longer resistant,” he said.

For example, when the NDSU scientist found rust in the aecia stage, he had the field aerially sprayed twice with fungicide except for one untreated test strip. In the treated field, the yield was 1,400 pounds, but in the untreated strip, the yield was 200 pounds, Markell said.”

Author: Roesler, S.
Affiliation: Farm & Ranch Guide.
Title: Type of fungicide on sunflowers not as vital as timing.
Source: Farm and Ranch Guide. July 16, 2010.