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Cercospora Leaf Spot of Gram

Cercospora Leaf Spot of Gram

Cercospora canescens

fungi

In a Nutshell

    Numerous small pale-brown necrotic ring spots surrounded by reddish brown margins on leavesSpots on branches and green podsSevere leaf spotting can lead to heavy defoliation at the time of pod formationFungal growth on and inside the pods can led to 100% yield loss

Hosts: %1$s

· Bean · Gram · Pigeonpea

Symptoms

Symptoms vary slightly depending on the strength of the pathogen and the plant type. Small water-soaked ring spots with a brown center and a yellow halo first appear on leaves 3-5 weeks after sowing the crop. At later stages of the disease, the spots become increasingly numerous and turn necrotic (dark brown) with reddish brown margins that appear slightly depressed. They can also develop on all other plant parts, especially on green pods. Under favorable environmental conditions, severe leaf spotting can lead to heavy defoliation at the time of flowering and pod formation. The fungus grows on the surface of and inside the pods, damaging them completely, and often leading to 100% yield loss.

Trigger

Leaf spot disease is caused by the fungus Cercospora canescens which infects blackgram and greengram alike. The fungus is seed-borne and can survive for periods of more than 2 years on plant debris in the soil. Following the root system it can travel huge distances within the soil. It also thrives in alternative hosts or volunteer crops in the field. The transmission to lower plant parts occurs via splattering water and air. Elevated day and night temperatures, moist soils, high air humidity or heavy stormy rains are favorable conditions for the spread of the fungus.

Biological Control

Hot water treatment of seeds is possible. The application of neem oil extracts are also effective in reducing the severity of the disease (higher pod and seed numbers, healthier pods, higher weight).

Chemical Control

Always consider an integrated approach with preventive measures along with biological treatments if available. If treatment with fungicides is needed, apply products containing benomyl, carbendazim or mancozeb. Application of carbendazim at first appearance of disease followed by spraying with hexaconazole reduces pod infection and enhances seed quality.

Preventive Measures

    Use seeds from healthy plants or from certified disease-free sourcesPlant resistant or tolerant varietiesPlant late to avoid damage of floral structuresLeave sufficient space between plants to maintain good ventilationMake sure that soil is well drainedEnsure good field hygiene by removing all plant residues and burning themClean contaminated equipmentAvoid working in the field while plants are wetMulch the plants to avoid transmission of fungi to lower leavesIntercrop with tall growing cereals and millets to avoid transmission between rowsCrop rotation with non-host crops is recommended