May
16

Entering Critical Wheat Stages to Control Disease with Fungicide

by Greg LaBarge, Fulton County

We are entering the critical stages for protecting susceptible varieties from foliar diseases and head scab. For the best effectiveness we need to closely stage wheat and apply these products at the right time based on disease pressure.

Looking at local wheat field late last week we ranged in stages from Feekes 5 to Feekes 8. As we get into Feekes 8, 9 and 10 these stages are the critical stages as we discuss foliar diseases. Feekes 8 to 10 expose the flag leaf which provides the majority of the energy used to in grain fillThe stages are defined as:

  • Feekes 8- The last leaf (flag leaf) is just showing through the whorl of the stem.
  • Feekes 9 is where the last leaf (flag leaf) is fully out of the whorl with the collar region exposed.
  • Feekes 10 is the boot stage where the head is inside the sheath of the flag leaf.

A line drawing of the stages can be found at: http://ohioline.osu.edu/b827/pdf/Wheat_Management.pdf

At stage 8 through 10 we need to scout for the common foliar diseases we see in Ohio which are primarily powdery mildew and Stagonospora leaf blotch. With powdery mildew 2-3 lesion on the leaf below the flag leaf justifies a spray. For Stagonospora we only need 1-2 lesions on that leaf below the flag leaf to trigger fungicide use. A guide to fungicides for foliar diseases can be found at: http://www.oardc.ohio-state.edu/ohiofieldcropdisease/wheat/OFCDwheatfungicides.pdf

Besides foliar disease we are concerned about Head Scab (Fusarium Head Blight). This disease is a big concern due to the potential for formation of vomitoxins the contaminate the harvest wheat and lead to dockage or rejection of the grain at the elevator. Fungicides are available that can suppress this disease but timing is critical and the product must be applied after foliar spray timing. The best timing to insure the highest payback is during the early stages of flowering or Feekes 10.5. The wheat head starts to flower from the center of the head and progresses to the base and tip as flowering progresses. More details on the products, effectiveness  and other factors to consider in head scab treatment can be found at http://corn.osu.edu/newsletters/2011/corn-2011-11/fungicide-application-and-vomitoxin-suppression

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