Small Grains

 

Cephalosporium Stripe

Ronda Koski, Colorado State University, Forest and Sade Tree Health Lab
Ned Tisserat, and Mary Burrows

Cause: Cephalosporium graminearum; a soil-inhabiting fungus

Occurrence: Winter wheat is the main economic host. Dryland winter wheat is much more severely affected that irrigated winter wheat. This disease is common throughout the Northwest, and Midwest.

Hosts: Many members of the grass family (Poaceae) are susceptible to this pathogen, including: Avena sp. (oats), Hordeum sp. (barley), Triticum species (wheat), Secale cereale (rye), Triticale hexaploide or Triticum secale or X Triticosecale (triticale), Bromus sp. (brome grasses), Dactylis sp.(crowfoot or orchard grass), and Poa sp. (bluegrasses). Spring-seeded grains escape serious infection by avoiding root injury due to winter frost heaving. Symptoms appear during jointing through heading, and develop on culms, leaf sheaths, and leaf blades.

Key Symptoms:

• Uneven stunting of tillers
• Conspicuous bright yellow (chlorotic), longitudinal stripes develop on green leaves of infected plants.
• Chlorotic stripes may initially appear diffuse or mottled.
• Tissues in chlorotic stripes eventually turn necrotic.
• Darkened veins develop within chlorotic stripes on culms, leaf sheaths, and blades.
• Usually only 1-3 stripes and discolored veins are present per leaf; entire leaf does not turn yellow.
• Yellow, mosaic-like symptoms may develop on leaves of seedling plants; such leaves are usually short lived.
• Darkened nodes develop on culms (stems) of infected plants nearing harvest.
• Premature ripening of infected plants that produce white sterile heads with shriveled kernels and outward turn awns.
• Symptoms may not develop on all leaves or on all tillers of diseased plants.

Look-alike symptoms:

• Severely infected fields have a yellowish cast that can be confused with yellowing caused by cool, wet soils and slow nitrogen uptake, leaf spot diseases, and/or wheat streak mosaic.
• Mosaic-like pattern that can develop on leaves early in the season could be confused with wheat streak mosaic (WSMV symptoms do not occur in the characteristic yellow stripes associated with Cephalosporium stripe).
• White head symptoms also can be caused by: take-all, fusarium crown rot, fusarium head blight (scab), common root rot, wheat stem maggot, or Hessian fly.

Significance: Yield losses result from reduced seed set and weight and premature death of tillers.Cephalosporium gramineum is soilborne and is the only true vascular fungal pathogen of wheat. In host plants, the hyphae inhabit and occlude xylem vessels, impeding the transport of water and nutrients. Pathogen hyphae enter the vascular tissues, where conidia are produced in the xylem and then transported upwards in the transpirational stream and then lodge and multiply at the nodes and in the leaves. Pathogen emits metabolites and occludes vessels in the course of leaf stripe formation. 

Favorable Conditions: Cephalosporium stripe tends to be more prevalent in areas with fluctuating winter temperatures and in the lower, wetter areas of a field. Pathogen survival is prolonged by soil pH in the range of 3.9 - 5.5.

Management Approaches:

• Soil-borne spores (conidia) serve as the primary inoculum, infecting roots during winter and early spring via wounds caused by soil heaving, frost injury, and  insects feeding on roots.
• Crop rotation and crop residue management will help to reduce soilborne inoculum (the pathogen persists in association with host residues on or within 8 cm of the soil surface).
• Good grassy weed control to prevent the green bridge.
• Deep tillage (greater than 8 cm).
• Some varieties are tolerant, but none are highly resistant.
• Late autumn seeding reduces incidence of Cephalasporium Stripe.

Laboratory Identification:

• Cephalosporium graminearum is easily recovered from symptomatic striped leaves and can be recovered directly from soil samples.
• Leaves or stems should be surface sterilized in 10% bleach for 30-90 seconds and plated on corn meal agar (CMA).
• In culture on CMA, colonies appear wet and gray, white, or pale yellow in color; hyphae being mostly submerged and produced in only limited amounts.
• Colonies may have a ‘ropey’ texture.
• Phialides (conidiophores) are short (1.0-2.0 X 4.0-10.0 um), hyaline, simple, and inconspicuous.
• Mucilaginous unicellular phialospores and blastospore conida (2.0-3.0 X 3.0-7.0 um) tend to clump together.
• On wheat straw, superficial raised sporodochia (< 1.0 mm in diameter) are produced.
• Sporodochium is yellow-brown in color, composed of a hymenial surface of branched, hyaline phialides (1.2 -1.5 wide by 10.0 – 30.0 um long), densely clustered on a thin stroma, glistening with mounds of mucilaginous unicellular, hyaline, ovoid conidia (0.8 - 1.5 um wide by 2.0 - 4.5 um long), these being smaller than those produced on artificial growing media.
• When dry, sporodochia appear flat and grayish-black and are easily dislodged from infected wheat straw; The sporodochial stage is considered to be saprophytic.

To isolate pathogen from infected wheat tissues:

• Sterilize symptomatic leaf and/or stem tissue in 10% bleach for 30-90 seconds
• Cut off ends of tissue and plate on corn meal agar (CMA).
• Colonies of Cephalosporium graminearum are white and "ropey" in texture.

Agrichemicals:

None currently listed on Greenbook.net

Product List for PEST:

Pesticide	Mode of Action	Product/Acre	Preharvest interval, remarks
		See labels
	RRestricted use pesticide. 1Labeled for chemigation. 2Generic active ingredient, several formulations.
	The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.

Categories: Small grains, Diseases, Cephalosporium Stripe

Date: 09/18/07