Foliar diseases in cereal grains are important to pay attention to as they can suppress photosynthetic mechanisms which are needed to produce a healthy grain head. Foliar diseases can lead to reduced vigor, growth, and yield. If your grain is infected earlier in the season there is a greater chance of yield loss, if favorable conditions remain.
Common Foliar Diseases of Grain
Septoria Leaf Blotch (SLB)
Affected Crops: Wheat, Barley, Rye
Septoria Leaf Blotch (Parastagonospora nodorum) infects mature leaves starting at the midrib. Symptoms appear as small necrotic spots and coalesce into brown oval lesions, surrounded by a yellow halo. As the lesion develops black pin-head structures (Pycnidia) can be seen which hold white to pinkish asexual spores. SLB infection increases as temperatures raise between 68-80 F and high humidity holds for long periods of time. Rain is essential for spore dispersal. Infection which occurs on the ear can lead to Glume blotch and cause infection to kernels.
Tan Spot
Affected Crops: Wheat, Barley, Rye
Tan Spot (Pyrenophora tritici-repentis) can be confused with SLB infection, spore identification is needed for the correct diagnosis. Tan Spot lesions develop in the mid to upper canopy and form lens-shaped necrotic lesions with a yellow halo. Once wet, the lesion darkens and produces olive-brown spores. The disease develops in a wide range of temperatures but prefers 60-82 F with long periods of moisture. Late season infection can cause bleaching on the grain spikes, along with the browning of glumes and kernels turning a red to pink hue.
Barley Yellow Dwarf (BYD)
Affected Crops: Wheat, Barley, Oats, Rye, Triticale
BYD is a viral disease which is transmitted by aphid feeding. The tips of leaves tend to have a yellow or red discoloration, which can resemble a flame. Plants infected with BYD may be stunted. This virus is usually seen in patches among a field, but the size and distribution are dependent on the aphid’s activity. Be sure to monitor your fields for aphids to reduce the risk of having BYD transmitted to your crop.
Powdery Mildew (PM)
Affected Crops: Wheat, Barley, Oats, Rye, Triticale
Powdery mildew (Blumeria graminis) prefers cooler conditions between 60-72 F with high humidity, 80% or higher. White, cottony fungal growth can be noticed on the upper surface of the leaf while the underside is yellow. As it matures, dark reproductive structures will form on the leaf surface. Plants can be more susceptible at times of rapid growth or after nitrogen application.
Leaf Rust
Affected Crops: Most common wheat, but can affect barley, rye, and triticale
Leaf rust (Puccinia triticina) appears as small, orange-brown or reddish-brown lesions on the leaf surface, it can be found on the leaf sheath during periods of high infection. Leaf rust is common and can occur more frequently when temperatures are mild, between 59-77 F. Most often, leaf rust can overwinter on early drilled crops or previously infected volunteer plants.
Management
It is important to scout fields for signs of diseases or insects often, so you can manage risk properly. For many of these diseases managing a good crop rotation with non-host crops, weed and volunteer control, and not overapplying nitrogen may help reduce the risk of an outbreak.
For more information and resources check out UVM Extension NW Crops and Soils Program- Grain Information
All photo credits: Bugwood.org