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Weather Forecast

Mar 14, 2017

Leaf Rust and Wheat Update

Wheat Growth

Wheat crops across the US continue to grow at an accelerated rate. Most of the wheat is in Feekes 8-10 (flag leaf to boot), and a field in the scouting program is already 50% headed as of today. Compared to last year, that puts us about 2 weeks or more ahead of schedule: in 2016, we had most fields in boot on March 28th.

We had a bit of a frost in some places last night, and some wheat in the more vulnerable stages could have been affected.

Leaf Rust

The unusually warm winter and periodic rains have resulted in high disease pressure this year. Stripe rust can be found in some fields, but in fields that were not treated at topdress (Feekes 5-6), leaf rust has increased significantly. Some fields remain completely clean, and others show pustules up to F1 leaf (just below the flag leaf). Fields with very heavy rust pressure may benefit from a treatment at Feekes 10 or before.

You may have heavy leaf rust in your wheat field if you come out orange after scouting.
Rust should be kept off the flag leaf, which contributes to 75% of the yield. At flowering, if there is 10% of the flag leaf surface covered by rust pustules, you can expect a 10% yield loss.

In this section of a leaf, pustules cover about 1% of the total leaf area. However, the yellow, necrotic areas are unable to photosynthesize and will also contribute to yield loss.

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