Wednesday, May 25, 2011

How is the wheat crop doing?

This week there isn’t much to report on corn and soybeans. Acreage is being piecemealed in as rains allow. Some corn fields that were planted in late April are just now emerging. With the potential for several more inches of rain this week, if we believe the weatherman, it may be longer until we see the county planted. So what about our third largest crop in the county? The wheat crop seems to be a mixed bag.

Most of the wheat crop is looking good this year. Fields braved a dry planting and rebounded through the rains this spring. As of Saturday the crop is between Feekes’ growth stage 10 and 10.1, which is boot to heading stage. In “boot” the wheat head is just about to emerge from the sheath. “Heading” obviously refers to the stage where the head is fully emerged. There are several management considerations that go along with heading that revolve around the term, dare I say, “head scab”. But more on that later. The biggest management decisions of variety selection, fertility and weed control are long behind us. We have also passed the optimal timing of fungicide applications for control of foliar diseases (Feekes 8 and 9).

The most recent trip to the field this past Saturday revealed that we do have foliar diseases present. The most common disease is Septoria tritici, a fungal disease that grows best in cool, wet conditions. There are also signs of Stagonospora leaf blotch, which prefers warmer, wet conditions. Right now we are at a transition time between the two diseases. Septoria will decline with the warmer temperatures of late May and early June. However, Stagonospora may increase with warmer temperatures. The good thing is that no fields scouted Saturday were above economic thresholds. An economic threshold is the point where applying a treatment like a fungicide will pay for itself in returned profits.

A major concern from this past week’s scouting is that wheat is approaching flowering. It can be as little as three to five days from the time the wheat head is fully emerged to when flowering begins. If during flowering the weather is warm and wet, there is a higher risk of infection by head scab. Sunday night the wheat head scab prediction tool forecasted a low risk for Darke County because wheat is not flowering. However, if rain persists for a few days before or during flowering we have an increased risk. There is no completely effective treatment for head scab. If a resistant variety is planted and an effective fungicide is timed correctly only 75% control can be expected. So how do we maximize control of head scab?

The first way to maximize control is proper timing of the fungicide application. The application needs to occur at flowering. Before flowering, the location of infection will not be protected, after flowering, the infection will have already occurred. The application needs to be timed to catch as many flowering plants as possible.

Second, apply an effective fungicide: Prosaro 421 SC, Proline 480 SC, or Caramba. A few of these fungicides also have activity on some foliar diseases like Septoria and Stagonospora. So it is typically not necessary to mix another fungicide in the tank. An exception would be if you have a variety that is susceptible to a foliar disease not controlled by the fungicide and that disease is present and at or near economic levels. Fungicide efficacy is rated at

Third is to apply the fungicide correctly. To provide adequate protection of the flowering wheat head thorough coverage is needed. If ground application is utilized apply fungicides in at least 10 to 15 gallons per acre with nozzles and pressures to produce fine droplets. Higher spray volumes can increase coverage. Be sure to utilize any additives on the fungicide label. Be sure to read the application directions on the label before utilizing the product.

If we see wet weather persist during flowering and the decision is made to spray, apply at flowering, apply an effective fungicide, and apply it correctly. Scout the field ahead of time to make sure wheat is flowering and see if other diseases are present at or near economic levels. Thresholds for our top three (with a susceptible wheat variety planted) are 1-2 lesions on the leaf below the flagleaf for Septoria and Stagonospora, and 2-3 powdery mildew lesions on the leaf below the flagleaf. For more information visit and click on ‘diseases’ on the right hand side of the screen or visit the CORN Newsletter at There are also factsheets available here in the office about our wheat diseases.

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