Pacific Pests, Pathogens & Weeds - Mini Fact Sheet Edition

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Bean Cercospora leaf spot (301)

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Photo 1. Leaf spot of Cercospora canescens on long bean.

Photo 2. Leaf spot of Cercospora canescens on long bean.

Photo 3. Round, angular and merging brown leaf spots of Cercospora canescens on mung bean. Many of the spots show the typical grey centre.

Summary

• Worldwide distribution. Common on food legumes,e.g., French bean, long bean, cowpea, mung bean. Minor fungal disease on older leaves.
• Small brown flecks, expanding to brown, round, to slightly angular spots with grey centres, up to 1 cm diameter. Brown margins, sometimes with yellow halos. Spots occur on pods.  
• Spores are spread in wind and rain. Survival is on seed, crop debris, and weeds.
• Cultural control: wide spacing (air movement); avoid overlapping crops; remove infected leaves; avoid overhead irrigation; weed; collect debris and destroy; crop rotation (maize, sorghum, root crops); tolerant varieties.
• Chemical control: treat seed: thriam, captan or mancozeb; sprays of copper, mancozeb if needed.

Common Name

Bean Cercospora leaf spot, Cercospora leaf spot

Scientific Name

Cercospora canescens. It is considered by some taxonomists to be identical with Celery early blight, Cercospora apii (see Fact Sheet no. 136), and the same as Cowpea Cercospora leaf spot, Pseudocercospora cruenta (see Fact Sheet no. 303).

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