Pacific Pests, Pathogens & Weeds - Mini Fact Sheet Edition

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Cowpea Cercospora leaf spot (303)

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Photo 1. Top and underside of a cowpea leaf showing the large reddish brown spots Pseudocercospora cruenta, mostly restricted by the veins.

Photo 2. As the spots caused by Pseudocercospora cruenta enlarge and merge, the leaves yellow and die.

Photo 3. Powdery spores form on the spots on the underside of leaves infected by Pseudocercospora cruenta.

Summary

• Worldwide distribution. On food legume, e.g., cowpea, French and mung beans. Pod numbers and seeds reduced on susceptible varieties.
• Reddish-brown fungal spots, up to 15 mm diameter, circular to angular, merging, often with a yellow halo. Leaves fall early.
• Spread by spores blown in wind, and splashed in rain. Survival is in debris left after harvest, and on alternative hosts.
• Cultural control: certified seed or seed with plant debris removed; interplant e.g., cowpea with maize or sorghum; remove volunteers; plant away from diseased crops; collect and destroy debris after harvest; resistant varieties.
• Chemical control: use mancozeb after flowering and when pods start to develop. Use 2-3 sprays per crop.

Common Name

Cowpea Cercospora leaf spot

Scientific Name

Pseudocercospora cruenta. Previous names are Cercospora cruenta and Mycosphaerella cruenta (the sexual state). Note that some taxonomists consider that this fungus is the same as Cercospora canescens (see Fact sheet no. 301).

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