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Arkansas Wheat: Stripe Rust Shows Early – A Concern Yet?

Owen Taylor
By Terry Spurlock, Extension Plant Pathologist, Trent Roberts, Extension Soil Fertility/Testing Jason Kelley - Wheat and Feed Grains Extension Agronomist - U. of Ark. February 16, 2017

Arkansas Wheat: Stripe Rust Shows Early – A Concern Yet?

Stripe Rust

An estimated 180,000 acres of wheat were planted in Arkansas during the fall of 2016, which was approximately 15,000 acres less than 2015. An extremely dry fall until late November may limited planting for some producers, but a weak grain market was the biggest factor reducing wheat acres this year.

An extremely warm October -February has led to excessive growth on many fields, even on fields that were planted relatively late. Overall precipitation has been below average for much of Arkansas this winter.

Some of the early-maturing wheat varieties that were planted early have started to joint, but a majority of the wheat has not yet started to joint. The current wheat growth stage is 2 weeks or more ahead of what would be considered normal for this time of year.

Arkansas Wheat Disease Update:

With the warm temperatures this winter and relatively little cold weather, it is not surprising that foliar diseases are being found. As of this week, stripe rust has been confirmed in 7 counties across eastern Arkansas (see map), but it is likely more widespread than the confirmed areas.

Stripe rust has been found this early in past years, so this is not all that unusual, but still is a concern for producers. Even though wheat varieties may be rated as resistant to stripe rust, it can still be found on those varieties at the current growth stages.

Click map to enlarge.

The wheat resistance genes to stripe rust become expressed closer to heading (known as adult plant resistance), so a variety that has stripe rust now may be resistant in the end.

The concern is that stripe rust strains can change, so a resistant variety last year may not be resistant this year.

If stripe rust is found now (especially on a known susceptible variety) it can be easily and economically controlled with propiconazole or tebuconazole foliar fungicides which can be tank-mixed with planned herbicide applications.

A fungicide application now will not last season long, but will control stripe rust to preserve yield, limit spread of spores to other fields and allow time to see if the resistance genes kick in.

If the variety is truly susceptible, another fungicide application will be needed near heading to protect yield.

Current wheat variety disease ratings can be found here.

Leaf rust and other foliar disease:

Other foliar diseases are showing up in addition to stripe rust. Last week leaf rust was at trace to low levels around the state and septoria tritici blotch and powdery mildew could also be found at low levels in some wheat fields.

Fungicide applications for these diseases are not recommended at this time. Typically optimal fungicide application timing for control of foliar disease occurs when the flag leaf emerges (Feekes 8).

Owen Taylor
By Terry Spurlock, Extension Plant Pathologist, Trent Roberts, Extension Soil Fertility/Testing Jason Kelley - Wheat and Feed Grains Extension Agronomist - U. of Ark. February 16, 2017