Using fungicides to suppress Fusarium head scab in wheat

Martin Nagelkirk, Michigan State University Extension, and Martin Chilvers<chilvers@msu.edu>, MSU Department of Plant, Soil and Microbial Sciences - June 05, 2019

Wheat fields are beginning to show signs of head emergence. This marks the time to consider applying fungicides to reduce the risk of head scab and leaf diseases.

Wheat head with flowers (anthers) mark the time for fungicide application. Photo by Martin Nagelkirk, MSU Extension.

The wet weather this spring has greatly elevated the risk of Fusarium head scab. At this point, the use of a fungicide at flowering is the best response for trying to curb the disease and suppress its associated mycotoxin (a.k.a. DON or vomitoxin). A fungicide application at the flowering stage offers the added benefit of helping keep leaf diseases in check.

Head scab is favored by moderate temperatures (56 to 86 degrees Fahrenheit) and high relative humidity (particularly in excess of 90%) around and during the flowering stage. Michigan State University Extension recommends utilizing the Fusarium head scab risk assessment tool. This prediction model provides a daily level of risks for specific locales. For southern Michigan where wheat is heading, the model is suggesting some of the highest risks levels that we have seen in recent years. For those in central Michigan where the flowering stage may still be a week away, the level of risk may be significantly less or even low depending on weather. The model is correct most of the time, but growers are also encouraged to rely on their knowledge of localized environments and their own experience.

Another important consideration is the innate resistance level individual varieties possess to fend off the disease. Below is a table providing a list of some common, established varieties and their respective resistance rating. Another good source of information is the Michigan State Wheat Performance Report. Table 3 of this updated report provides the resistance ratings for varieties from the 2018 season.

Relative susceptibility of winter wheat varieties to Fusarium head scab
Soft white winter wheat		Soft red winter wheat
variety	rank*	variety	rank*	variety	rank*	variety	rank*
Ambassador	VS	Pioneer 25R40	S	Branson	MS	MCIA Roane	MS
Skeet Safety	VS	Wellman 206	S	Red Devil	MS	Pioneer 25R50	MS
Jupiter	S	Hopewell	S	AgriMax 413	MS	Red Dragon	MR
AC Mountain	S	Shirley	S	DynaGro 9223	MS	DF 112R	MR
Aubrey	S	DynaGro 9243	S	Pioneer 25R39	MS	Pioneer 25R25	MR
Pioneer 25W36	S	Pioneer 25R47	S	DF 105R	MS	Agrimax 415	MR
E6012	S	Red Ruby	S	Sienna	MS	Steyer Hunker	MR
Venus	S	Pioneer 25R62	S	Rupp 907	MS	L334	MR
DynaGro 9242W	MS	Whale	S	Sunburst	MS	Rupp 972	MR
Pioneer 25W43	MS	DF 109R	S	DynaGro 9171	MS
Syngenta 901	MS	Agrimax 438	S	AgriMax 444	MS
Pioneer 25W31	MS	DF 045	S	DynaGro 9053	MS
DynaGro 9353W	MS	SC1342	S	DynaGro 9042	MS
		DynaGro 9522	S	Wellman 123	MS
* the relative susceptibility of varieties are ranked as VS (very susceptible), S (Susceptible), MS (moderately susceptible), or MR ( moderately resistant)

Head scab map — The daily updated national head scab assessment tool uses colors to indicate risk level (Map as of 6-4-2019)

Ground application is generally recommended for applying wheat fungicides. However, aerial application of fungicides may be necessary where wet conditions prohibit ground rigs from operating. Fungicides applied by air may have reduced head deposition compared to ground rigs, but they still can offer significant protection against head and leaf diseases. See Aerial Application of Fungicides from work in North Dakota for application recommendations.

The best fungicides for head scab include Prosaro, Caramba and Miravis Ace. These products usually reduce the severity of the disease and the associated mycotoxin (D.O.N. or vomitoxin) level by half if applied correctly. To optimize the benefit of these fungicides, growers should treat 2 to 7 days after the heads have begun to flower. An information piece, Managing Fusarium head blight, is available as a resource.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).