Barley Stripe Mosaic (virus): Barley stripe mosaic is a seed-borne virus which causes yellow or light-green stripes or streaks of the leaves.
Barley Yellow Dwarf Virus (virus): Yellowing of leaves is the first visible sign that a plant is diseased. When infection occurs in a plant during the seedling stage, the leaves turn a bright golden yellow, usually beginning at the tips and progressing back along the edges. In very susceptible varieties, plants infected in the seedling stage are severely dwarfed and may grow less than six inches tall. They produce more tillers than healthy plants but form no heads. Several species of aphids can carry the virus from infected grasses to barley. Use resistant varieties (See Table 1 Below).
Basal Glume Blotch (bacterium – Pseudomonas atrofaciens): Basal glume blotch on barley is caused by a bacterium. It is caused by the same bacterium that occurs commonly on wheat. The symptom of basal glume blotch is dull brownish-black, discolored area found at the base of each glume covering the kernel. The discoloration is more pronounced on the inside than on the outside of the diseased glume. The base of a diseased kernel shows a discoloration varying from faint brown to charcoal black with the color depending upon the severity of the attack. Leaves affected by this disease organism show small, dark, water-soaked spots. These spots tend to enlarge and turn yellow and finally brown as the tissue dies. The use of clean and treated seed will reduce the severity of this disease.
Foot Rot, Take-all, and Rhizoctonia Root Rot and Sharp Eyespot: These diseases affect both barley and wheat and are described in the wheat section.
Leaf Blotch (fungus – Septoria passerinii): The spots characteristic of leaf blotch are elongated and yellowish-brown, and their ends have indefinite margins. Numerous dark-brown fruiting bodies develop in rows between the veins in the dead, straw-colored parts of the spots. Control is the same as for spot blotch.
Leaf Rust (fungus – Puccinia hordei): Small, round yellow or yellowish-brown pustules appear on the leaves (See Photo). Infected leaves eventually die. Leaf rust of barley does not infect oats or wheat. The development of resistant varieties is currently the only practical means of control (See Table 1 Below).
Nematodes: Lesion, spiral, stubby root and stunt nematodes feed on the roots and can result in poor root development. Plants will be stunted and in most cases show an off-color as a nutritional deficiency. Frequent turning of the soil during summer months tends to lower populations.
Net Blotch (fungus – Pyrenophora teres): Net blotch of barley is principally a leaf disease. The spots are internal with a characteristic netting (See Photo). The netted pattern, formed by the arrangement of brown pigment in transverse and longitudinal lines, can best be seen if the leaf is held against the light. The elongated, brown-netted areas finally cover most of the leaf and destroy it usefulness. The fungus causing net blotch may be carried on the seed or infection may come from old straw or stubble. Crop rotation, plowing old straw and stubble, and seed treatment will aid in prevention of this disease. Avoid susceptible varieties (See Table 1 Below).
Powdery mildew (Erysiphe graminis); Gray, fluffy threads of the fungus can be observed on the upper surface of the leaves and leaf sheaths. The fungal strands penetrate and invade the leaf tissue. As the disease progresses, the leaf turns yellow and is gradually killed. Spores of the fungus are carried from plant-to-plant by wind currents. While the disease can be controlled with fungicides (See Table 2 Below), such controls may not be economical. Some resistant varieties are available (See Table 1 Below).
Smut (fungi – Ustilago hordei, U. nigra, U. nuda): Three smuts occur on barley in Texas, but with seed treatment fungicides now available (See Table 2 Below), each can be controlled. Covered smut (U. hordei) is noticed at heading time. Hard, black masses of smut, each covered with a grayish membrane, are found in place of kernels. Semi-loose smut (U. nigra) destroys the floral parts and entire head. Spores of the nigra smut are carried within the husk covering or on the seed. Loose smut (U. nuda) is similar to semi-loose smut except the smut fungus is internally seed-borne.
Spot Blotch (fungus – Bipolaris sorokiniana): Spot blotch infection starts as dark brown-to-black spots on sheaths that cover the young shoots. The infection progresses inward and sometimes kills the seedlings below the surface of the ground, but more often it kills the seedlings after emergence. Diseased seedlings are dwarfed and tiller excessively. The leaf spot has round to oblong dark brown lesions. Spots may coalesce to form blotches. As crown rot, the disease develops at or near the soil line. Crown roots may be rotted and tillers killed. The pathogen can be soil- or seed-borne, and may be carried on crop residue. Seed treatment with a fungicide (See Table 2 Below), reduces losses from seedling infection. Clean plowing of crop residue and crop rotation will aid in control.
Stem Rust (fungus – Puccinia graminis): Pustules break through the stem and leaf tissue. Rusted stems turn brown, become dry and brittle and may lodge. Control is the same as for leaf rust.
Table 1: Disease Susceptibilities of Barley Varieties
|Variety||Leaf Rust||Powdery Mildew||BYDV||Net Blotch|
|R = Resistant, MS = Moderately Susceptible, MR = Moderately Resistant, S = Susceptible|
Table 2: Chemical Treatments for Barley Disease
|Net Blotch Seed Treatment||Powdery Mildew Fungicides||Smut Seed Treatment Fungicide|
|Imazalil||Triadimefon, Phopiconazole, Tribasic copper, Sulfate + sulfur||PCNB, Triadimenol, Carboxin + Thiram, Carboxin + Captan, Carboxin + Maneb + Lindane, Carboxin + PCNB, Mancozeb|