Safflower Cercospora Leaf Spot

From Bugwoodwiki

Author: Howard F. Schwartz and David H. Gent

P. cichorii
Scientific Name
Pseudomonas cichorii
(Swingle 1925) Stapp 1928
Common Names and Diseases
bacterial leaf spot, bacterial blight

Identification and Life Cycle

Cercospora leaf spot of safflower is caused by the fungus Cercospora carthami. The disease cycle is initiated when wind-blown or water-splashed conidia land on safflower and germinate in the presence of free moisture. The fungus infects plant parts through natural openings, wounds, or by direct penetration. Heavy and continuous early morning dew or other free moisture is essential for infection, and disease is most severe during warm, moist weather. The Cercospora leaf spot pathogen is disseminated by wind, water-splashing, and movement of infested plant material. The pathogen survives between safflower crops in and on infested crop debris, and perhaps as a pathogen on weeds.

Plant Response and Damage

Cercospora leaf spot symptoms can develop at any stage of plant growth, and appear as round to irregularly-shaped brown spots. Lesions are slightly sunken and often have concentric rings and a yellow margin. Diseased leaves may become mis-shapen and often have interveinal necrosis. Grayish sporulation by the pathogen is apparent during moist weather. Bracts, stems, nodes, and flower buds can also be infected. Seed is not produced in infected flower buds. The disease is of minor concern in the High Plains region, and generally does not require management.

Management Approaches

Biological Control

No biological control strategies have been developed for Cercospora leaf spot.

Cultural Control

Few specific cultural control strategies have been developed for Cercospora leaf spot. . Crop rotations of three-years or longer to non-hosts (small grains or corn), thorough incorporation of crop debris, and avoidance of overhead and excessive irrigation will likely reduce the incidence and severity of Cercospora leaf spot.

Chemical Control

Chemical controls are not necessary for Cercospora leaf spot management.

Product List for Cercospora Leaf Spot:

Pesticide Product per Acre Application Frequency (days) Remarks
Trilogy 2 pt 7-14 days Maximum of 2 gallons; 0 day PHI

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.