Barley yellow dwarf is starting to develop in winter wheat. Barley yellow dwarf is caused by the Barley yellow dwarf virus (BYDV). This disease usually becomes more distinct at flag leaf emergence. A typical symptom of Barley yellow dwarf is the purplish-yellow color of infected leaves, especially the flag leaf.
Winter wheat is starting to head. It is important to monitor weather conditions from when wheat is heading until flowering to decide the need for fungicide application to manage Fusarium head blight (FHB). Wheat is most susceptible to FHB around the flowering growth stage because the fungal pathogen that causes it infects wheat through the flower. Rainfall during wheat heading through post flowering is the main risk factor for FHB.
Some winter wheat fields scouted last week had patches of thin plant stands. Poor plant stands can be attributed to low soil moisture and winter kill due to lack of snow cover or crown and root rots. Determining the cause of the poor plant stand may help inform management decisions for the future wheat crop.
SDSU Extension will host Wheat Walks in the Pierre and Wall areas on May 25, 2017 and in the Clark area on June 1, 2017. The goal of these events is to provide wheat producers with the latest information to effectively manage their crop. SDSU Extension experts will be on hand at each location, providing expertise in plant pathology, weed control, entomology, soil fertility and agronomic information.
The winter wheat growth stage as of the week of May 15 ranges between jointing and flag leaf emergence. The flag leaf emergence growth stage often coincides with fungal disease development, mainly due the microclimate created by canopy closure. Flag leaf and the leaf below flag leaf should be protected from fungal diseases because these leaves contribute the most to grain yield.
Stripe rust was found in one winter wheat field in Hand county last week. A few plants at the edge of the field had stripe rust pustules. This is the first observation of stripe rust in 2017 in South Dakota. Stripe rust forms yellow/orange lesions (pustules) full of millions of spores. These spores are blown by wind into other fields.
While scouting winter wheat fields throughout Central and Eastern South Dakota last week, there were several fields that were exhibiting the tell-tale signs of leafhopper feeding injury. After a little additional scouting, it was determined that the fields were infested with large populations of the aster leafhopper (Figure 1). Aster leafhoppers are capable of producing feeding injury that is referred to as “hopper burn.”
In South Dakota, the most commonly encountered mites in wheat are wheat curl mite and brown wheat mite. In addition to feeding, wheat curl mites are vectors of Wheat streak mosaic virus. Brown wheat mites can build up large populations and injure wheat through feeding. There are other species of mites that may also be observed in wheat, but generally do not reach populations large enough to cause significant injury.
A few winter wheat fields in Central South Dakota have been found with wheat streak mosaic disease. Incidence of this disease varies from a few plants to large portions of the field with yellowing leaves. This disease can be confused with herbicide injury, water lodging or nitrogen deficiency. Wheat streak mosaic is caused by Wheat streak mosaic virus (WSMV).
We have not received any reports of cutworm issues in winter wheat yet this spring. However, it has been a cooler spring compared to 2016 when cutworms were causing issues as early as mid-March. It is possible that cutworm emergence may still occur and scouting for these pests may be necessary. There are two species of cutworms that feed on winter wheat in South Dakota.