HPIPM:Ascochyta Blight

Taxonomy

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

Scientific Name

Ascochyta rabiei

Scientific Name Synonyms

Phoma rabiei

Didymella rabiei

Mycosphaerella rabiei

Phyllosticta rabiei

Common Name

Ascochyta blight of chickpea

Ascochyta Blight (Ascochyta rabiei)

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

Updated by: Mary Burrows

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Cause

Ascochyta blight of chickpea is caused by the fungus Ascochyta rabiei. The pathogen only infects chickpea, but related pathogens attack lentil and pea. Ascochyta blight is a very destructive disease in the Northern High Plains, and can cause heavy losses when environmental conditions favor the pathogen.

Symptoms

Infected plants exhibit dark, sunken lesions that soon take on a concentric ring appearance. Small, dark fruiting bodies called pycnidia are produced inside the lesions. Stem lesions often lead to girdling of the stem and plant tissue death above the point of infection. On pods, the lesions usually are circular with a darker border and they often display concentric rings and fruiting bodies inside the lesions also. Some infected seeds have dark spots /areas on the seed surface and often they are shriveled. However, other chickpea seeds that test positive show few visible symptoms.

Impact of Disease

Ascochyta blight can cause up to 100% yield loss and can reduce crop quality on untreated susceptible varieties.

Life Cycle of the Pathogen

Infection is initiated by sexual spores (ascospores) forcibly discharged up in the air from specialized fruiting bodies (asci) and can move several miles via wind currents. Asexual spores are produced during the season from fruiting bodies (pycnidia) on actively growing plants. These spores exude out of the pycnidia in very high numbers and move short distances via rain splash and wind. Spores germinate and infect chickpea optimally when temperatures are mild (68 to 77ºF) and free moisture is present. The pathogen survives between chickpea crops in and on infested seed, crop residue, and volunteer chickpea.

Management Approaches

Biological Control

No biological control practices have been developed for Ascochyta blight.

Cultural Management Practices

Plant only high quality seed free from the Aschochyta blight pathogen. Resistant varieties are available, and should be planted; the varieties Sanford, Dwelley, and Myles are considered resistant. Practice a three- to four-year rotation to nonhosts such as small grains. Eliminate chickpea residues and volunteer chickpea to reduce pathogen survival and overwintering.

Chemical Management Program

Chemical controls are essential for Ascochyta blight in most years, but are most effective when integrated with sound cultural control practices. Three or more fungicide applications are often necessary to effectively control Ascochyta blight when conditions are highly favorable for disease development.

NOTE: Strobilurin resistance has been identified in North Dakota and Montana. Strobilurins should not be used for Ascochyta control on chickpea.

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.