Damage to heads from frost/freeze is beginning to appear as white awns/florets in wheat heads. Thankfully this damage is very minor in area wheat fields right now.
Barley yellow dwarf is also appearing in fields and is noticeable by flag leaves with a yellow/purple color. This is a disease vectored by various aphid species. The aphid in this photo is a corn leaf aphid and I’m seeing these in wheat as well right now in addition to lady beetles which are feeding on them. We also observed aphids last fall and were concerned about them potentially vectoring this disease. I would say this is my least favorite wheat disease because you can do many things correct with wheat just to have this one show up and affect yield.
Also seeing some loose smut in fields which again is fairly minor. Both loose smut and stinking smut (common bunt) can be prevented by using a seed treatment fungicide at planting. Often these diseases occur in fields where wheat has been planted and smut has occurred before and when using bin-run wheat that has not been treated with a seed treatment fungicide. Also notice all the yellow ‘flecks’ on these leaves which are indicative of fungal infection (most likely rust) on these leaves.
According to research, wheat is susceptible from flowering through soft dough development stage. “Typical” fungicides used for control of fungal leaf diseases are off-label thus illegal to apply once the wheat has flowered and they do not have activity on the Fusarium fungus causing scab of wheat. Management for scab includes the use of the preventive fungicides Caramba or Prosaro. Both are labeled for headed and flowering wheat. There’s a 30 day pre-harvest restriction for both. Rainfast varies from ¼ hour to 2 hours or when dry depending on environmental conditions. Both fungicides can help prevent scab and control rust on the plant.
Research from the US Wheat and Barley Scab Initiative (which is a combined effort of several Universities in the U.S. and Canada) has found that the best prevention using these products occurs when wheat is headed and 30% of the plants are in the beginning flower stage. Application within five days of these criteria still showed positive results. This research also showed that application before or after this time period greatly reduced effectiveness of preventing scab. Understandably, the economics of fungicide application are difficult in wheat, yet, if you are aiming to make one application, this could be your best option for both scab prevention and controlling rust in your plants. The risk map for scab can be found at: http://www.wheatscab.psu.edu/. With wheat at heading to beginning flower and rain/humidity this risk in reality could be higher for us.
Questions have been rolling in regarding dead leaves in the mid to lower wheat canopy. Wheat is heading in much of South Central Nebraska and in some cases has begun to flower. When considering a fungicide application, once your wheat has begun to flower, there are only certain products that are labeled for use. These include but are not limited to fungicides such as Proline, Folicur, and Prosaro. All of these have a 30 day pre-harvest restriction and can only be applied up to 50% flowering. For more information on all fungicides, rates, and pre-harvest restrictions for wheat, please check out this resource from Dr. Stephen Wegulo, UNL Extension Wheat Pathologist. Below is a short video of me scouting a wheat field so you know what to look for in your fields. Fungicides will not help leaves affected with barley yellow dwarf as that’s caused by a virus; however, with the amount of stripe rust in our canopies and seeing it on the flag leaves already in addition to the rain and humidity allowing for increased risk of Fusarium Head Blight (scab), I still feel a fungicide is a good option.