HPIPM: Ascochyta Blight Pea

Taxonomy

Domain	Eukarya
Kingdom	Fungi
Phylum	Ascomycota
Subphylum	Pezizomycotina
Class	Dothideomycetes
Subclass	Pleosporomycetidae
Order	Pleosporales
Family	Didymellaceae
Genus	Ascochyta
Species	Ascochyta medicaginicola

Scientific Name

Ascochyta medicaginicola var. medicaginicola

Scientific Name Synonyms

Phoma medicaginis var. medicaginis

Common Name

Ascochyta Blight Pea (Scientific name )

Author: Howard F. Schwartz, David H. Gent, Martha Mikkelson,and Jack Riesselman

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Cause

Ascochyta blight of pea is caused by several fungi, including Phoma medicaginis var. pinodella, Ascochyta pisi, and Mycosphaerella pinodes.

Symptoms

Ascochyta blight symptoms can develop on leaves, pods, and stems. Stem and leaf lesions appear initially as irregularly shaped tan spots with dark brown margins. Stem lesions develop at or near the soil line and are slightly sunken. Pod lesions are circular, sunken and tan colored with dark margins.

Impact of Disease

Infected young plants may die or survive in a weakened condition. Later in the season, leaf, stem, and pod spotting can be severe with slight to severe losses in yield and quality. The disease is most damaging during cool, wet weather.

Life Cycle of the Pathogen

The primary inoculum source that initiates disease epidemics is airborne ascospores released from fungal fruiting bodies (pycnidia and perithecia) on infested crop debris. Ascospores germinate and infect pea over a range of tempatures (40 to 95ºF) when free moisture is available. Fungal fruiting bodies (pycnidia) develop on infected leaves, which produce airborne spores (conidia) when moisture is available. Plants become increasingly susceptible as they mature and are most susceptible from flowering to full maturity. The Ascochyta blight pathogens are disseminated in and among pea fields by windborne spores and splashing water, and survive between pea crops on infested seed and crop residue.

Management Approaches

Biological Control

No biological control strategies have been developed for Ascochyta blight of pea.

Cultural Management Practices

Plant high quality seed free from the Ascochyta blight pathogens. Practice a long (four years or longer) rotation to nonhosts such as small grains and corn. Promptly and thoroughly incorporate crop residues after harvest to reduce pathogen overwintering and survival. Delaying planting so plants mature during warmer weather can significantly reduce disease severity. Resistant varieties have been developed and should be planted if Ascochyta blight becomes a consistent problem.

Chemical Management Program

Chemical controls are most effective when integrated with sound cultural practices. If using nitrogen-fixing inoculants, add twice the amount of Rhizobial inoculant and put inoculant in the seed furrow, not on seed; or add inoculum no more than 2 hours before planting.

See Pulse Crop Foliar Fungicides and Pulse Crop Seed Fungicides for fungicide recommendations.

Consult pesticide labels for additional rate, application, and safety information. Additional information and current labels can be found at http://www.greenbook.net or http://www.cdms.net.

References

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.