To Spray or Not:
This is a no-brainer- ABSUOLUTELY SPRAY! We are relatively wet and humid, and with the warm weather upcoming, a scab fungicide is absolutely needed and will ACROSS THE BOARD pay for itself- both in yield, Fusarium damaged kernels and in vomitoxin control.
Prosaro 6.5 oz/acre or Caramba 14 oz/acre are the top of the line products and the products of choice. Folicur (or tebuconazole generics thereof) do work OK, but they are NOT in the same league as Prosaro or Caramba on level of control. Proline is also possible, and it falls between tebuconazole and Prosaro on control level.
Crop Stage & Variable Heading Dates:
Full heading. We need to get all heads emerged. If a head is not emerged, a scab spray will not protect that head.
- So how do I manage wheat if the main head is out, but the tillers are lagging? There is no great answer here, but my advice is to determine where the maximum yield is- and that usually is the main spikes. If we wait for the tillers, we risk getting some scab in the main spike, but if we spray for the main spike, some tillers will still be in the boot and will be missed.
- The anthers on some heads are white, so it has flowered a while ago. Will a late application still protect the head? The answer here is YES and a little NO. We cannot CURE an infected head, but we CAN stop the scab from spreading to non-infected spikelets, we CAN protect the seeds above the infection point, and we DEFINITELY CAN reduce DON (vomitoxin) levels in the developing grain.
Application and Adjuvants:
Coverage is critical. This is a case to slow down a little, keep water rate UP and work on coverage. 15 gpa will generally look better than 10 by ground, if you can. 20 is not necessary, but 12-15 seems to be the magic number. DO apply an adjuvant- straight NIS is the preferred product. Adding fertilizers with scab products often can lead to leaf burn. Local experience will dictate whether any fertilizer application in conjunction with fungicide is feasible.
What about Leaf Diseases- rusts, powdery mildew, tan spot or Septoria?
The first thing is to protect the FLAG LEAF and FLAG-1 LEAF at all costs! These two leaves provide a vast majority (2/3 up to 75%) of the input into developing head. Rusts keep rolling along in South Dakota. As I have said before, stripe rust can be very damaging and needs to be controlled. Tan spot and Septoria can continue along throughout the season as well.
- The new kid this year seems to be POWDERY MILDEW. Look for dusty tannish-gray pustules on the wheat leaves. Pustules start at the bottom of the plant, but can move upward quickly.
- A fungicide application will stop these diseases in their tracks, but remember that lost leaf area is LOST- dead is dead and we cannot get that green tissue back. Scab fungicides are excellent fungicides for leaf diseases.