Fungicides Protect Sunflowers From Rust

Sunflower Rust

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.

Fungicides Cover for Failure of Crop Breeding for Rust Control in Dry Beans

Bean Rust

Bean Rust

Bean rust usually is observed first as discrete pustules which are filled with cinnamon-brown spores, which leave a dusty brown streak when rubbed. The last bean rust epidemic in North Dakota in the 1990s caused in excess of $10 million in crop losses. Following the introduction of rust-resistant dry bean varieties produced through crop breeding, rust was not a problem until 2008 when a new race appeared which could overcome the resistance. Since the new race was first detected, rust has re-appeared every year. However, the disease has caused little damage due to frequent fungicide applications for white mold (most of the fungicides applied for white mold have some efficacy against rust).

“Between 1996 and 2008, bean varieties with resistance to rust made the threat of a bean rust epidemic in North Dakota very low. However, in 2008 a new race of the pathogen was identified in North Dakota. The new race has the ability to cause disease on the only commonly used effective resistance gene in common varieties. In 2010, the new race spread throughout North Dakota and into northwestern Minnesota. With the spread of the new race, the region is at risk again for the multimillion dollar yield losses caused by bean rust decades ago.

A fungicide application can be a very effective tool for rust management… In rust trials conducted between 2009 and 2011, all fungicides tested reduced rust severity… Because of this, a secondary benefit to a fungicide for white mold (which occurs at early bloom, R1-R2) is that the application may offer some measure of rust protection.

A fungicide application is most effective soon after the disease is found, making scouting for the disease critical.”

Authors: Markell, S., Olson, L., and Acevedo, M.
Affiliations: NDSU Department of Plant Pathology
Title: Dry edible bean rust
Source: Plant Disease Management. NDSU Extension Service. January 2012. Available at:

Fungal Growth on Sugarbeet Leaves Would Lower U.S. Sugar Production

Fungicide Treatment (Left: Treated - Right: Untreated)

Fungicide Treatment (Left: Treated – Right: Untreated)

The Red River Valley in North Dakota and Minnesota is a major sugarbeet production area. About ½ of U.S. sugar comes from sugarbeets. A disease on the leaves damages the plant’s ability to produce extractable sucrose in the roots. Fungicides kill the fungus before the damage is done to the plants.

“Cercospora leaf spot is the most economically damaging foliar disease of sugarbeet in Minnesota and North Dakota. The disease reduces root yield and sucrose concentration, and increases impurity concentrations resulting in reduced extractable sucrose and higher processing losses.”

“It is difficult to combine high levels of Cercospora leaf spot resistance with high recoverable sucrose in sugarbeet. Consequently, commercial varieties generally have only moderate levels of resistance and require fungicide applications to obtain acceptable levels of protection against Cercospora leaf spot under moderate and high disease severity.”

Authors: M.F.R. Khan1 and A.L. Carlson2
1North Dakota State University & University of Minnesota; 2Plant Pathology Department, North Dakota State University
Title: Efficacy of fungicides for controlling Cercospora leaf spot on sugarbeet.
Publication: Sugarbeet Research & Education Board of Minnesota and North Dakota. 2011 Research report available at: