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How is the wheat crop doing?
Justin Petrosino, ANR Extension Educator
OSU Extension, Darke County
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 http://www.oardc.ohio-state.edu/ohiofieldcropdisease/wheat/OFCDwheatfungicides.pdf.
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 http://agcrops.osu.edu and click on ‘diseases’ on
the right hand side of the screen or visit the CORN Newsletter at http://corn.osu.edu/.
There are also factsheets available here in the office about our wheat
diseases.
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