Common bunt
Wheat kernels infected by common bunt have a gray-green color and are wider than healthy kernels. Diseased kernels can be seen in developing wheat heads but are often not detected until harvest. The outer layers of diseased kernels remain intact initially but are easily broken during grain harvest, releasing masses of black, powdery spores. The fungus produces chemicals with a fishy odor, which sometimes causes this disease to be referred to as “stinking smut.”
Management: Fungicide seed treatment, disease-free seed sources.
Fusarium head blight
Symptoms of Fusarium head blight include tan or light brown lesions encompassing one or more spikelets. Some diseased spikelets may have a dark brown discoloration at the base and an orange fungal mass along the lower portion of the glume. Grain from plants infected by Fusarium head blight is often shriveled and has a white chalky appearance. Some kernels may have a pink discoloration.
Management: Avoid the most susceptible varieties and planting into corn residue, foliar fungicides.
Loose smut
The normal head tissue of plants infected by loose smut is completely replaced with dark masses of fungal spores, giving the heads a black powdery appearance. It is possible to see heads damaged by loose smut while much of the head is still inside the boot. Only the central stem of the head is left after the spores are released.
Management: Fungicide seed treatment, disease-free seed sources
Sooty head molds
Sooty head molds are characterized by a dark green or black mold growth on the surface of mature wheat heads. These molds are part of a naturally occurring complex of organisms that help to decay dead plant debris. Sooty molds are most common when mature wheat is subjected to repeated rains and delayed harvest. This disease also may affect plants that have been damaged by root rot. The sooty head mold growth is normally superficial. Its affect on grain is thought to be minor, but it can make for dusty harvest operations. Sooty molds can contribute to a discoloration of the grain called “black point.”
Management: Generally impractical or not needed
Stagonospora nodorum blotch
This disease causes dark brown or purple lesions on heads. Lesions are often more intense at the top of the glume, with brown streaks or blotches extending down toward the base of the spikelet. The presence of tiny fungal reproductive structures embedded in the tissue can confirm the diagnosis but will require significant magnification.
Management: Genetic resistance, foliar fungicides, crop rotation, fungicide seed treatment
Bacterial streak
Early symptoms of bacterial streak include small, water-soaked areas between leaf veins. These water-soaked areas become tan streaks within a few days. When the disease is severe, streaks may merge to form large, irregular areas of dead tissue. When dew is present, the bacteria causing this disease may ooze from the lesions and dry to form a clear, thin film. This film f lakes easily and is visible when the leaf is viewed from different perspectives.
Management: Avoid highly susceptible varieties
Leaf rust
Small,
orangish-brown lesions are key features of leaf rust
infections. These blister-like lesions are most common
on leaves but can occur on the leaf sheath, which
extends from the base of the leaf blade to the stem node. Lesions caused by leaf rust are
normally smaller, more round,
and cause less tearing of the leaf tissue than those
caused by stem rust.
Management:
Genetic resistance, foliar fungicides
