iCowApp

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Cowpea Mosaic Diseases

Damping-off Diseases

Bacterial Blight

Anthracnose

Powdery Mildew

Leaf Spots

Brown Blotch

Rust

Cowpea Wilt

Southern Blight

Charcoal Rot

(Sclerotium rolfsii)

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It attacks roots and stems of cowpeas. The first visible symptom of southern blight is a progressive, yellowing and wilting of the foliage beginning on the lower leaves.

The plant dies within a few days after the first symptoms appear. During warm, moist conditions, the coarse, white mycelium of the fungus makes characteristic fan-shaped patterns of growth on the stem at the soil line.

In this white mat of the fungus, numerous smooth, round, light-tan to dark-brown mustard seed-like bodies called sclerotia are formed.

What to do:

• Practise good field sanitation.
• Practise crop rotation with non-legumes.
• Plough the soil deep.

(Fusarium oxysporum f. sp. tracheiphilum)

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Fusarium wilt usually causes the lower leaves on one side of the plant to turn yellow.

Infected plants usually are stunted and wilted as the organism develops in the food and water conducting tissues.

Brick red tissue can be observed in the stem when it is split lengthwise.

What to do:

• Use resistant varieties, if available.
• Control root-knot nematodes since nematodes increase plant susceptibility to Fusarium wilt.

(Uromyces vignae)

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Small, reddish-brown pustules (blisters) appear on both upper and lower leaf surfaces.

Rust can develop rapidly, resulting in severe leaf damage and defoliation.

What to do:

• Use sulfur based products or potassium carbonate. Do not spray sulphur when it is hot, as it can burn the foliage and flowers.

(Colletotrichum truncatum)

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The fungus causes pre-emergence and post-emergence damping off when infected seeds are planted.

The former rots the seed before emergence from the soil while post-emergence kills the seedlings after emergence.

The disease also attacks the foliage, stems and pods. Sunken, oval spots may be seen on stems; circular spots on leaves.

Lesions are reddish-brown. Under prolonged wet weather heavy defoliation occurs.

During late reproductive stages, infected tissues are covered with black fungal fruiting bodies, which produce minute black spines (setae) that can be seen with the unaided eye.

It is transmitted through infected seeds and survives in crop debris.

What to do:

• Use certified disease-free seeds.
• Use resistant varieties where available.
• Practise good field sanitation.

(Cercospora sp., Aristastoma sp., Ascochyta sp., Colletotrichum sp., Stagnospora sp.)

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Leaf spots are various sized often yellowish in colour or with a yellow halo, others brown to purplish; These normally develop first on lower leaves.

With Cercospora leaf spot a dark, mouldy growth develops on the lower leaf surface corresponding to the spot.

Leafspot diseases are most serious during periods of prolonged moist weather and on late plantings.

Severe leaf spotting results in defoliation with subsequent yield reductions.

What to do:

• Use certified disease-free seeds.
• Practise crop rotation with non-legumes (e.g. cereals).
• Avoid cultivating fields when foliage is wet.

(Xanthomonas axonopodis pv. vignicola)

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This disease appears as tan to brown angular leaf spots with yellow margins on leaves, pods, and stems.

It may cause severe defoliation during periods of high humidity. It is seed-borne.

What to do:

• Use certified disease-free seeds.
• Avoid working in the fields when it is wet.
• Practise good field sanitation.

Credits: Biovision-Infonet

These viruses produce a mosaic pattern on cowpeas. They may be found singularly or in combination with others. They cause irregular light and dark green mosaic patterns on the leaves.

Some viruses cause thickened, malformed leaves. The mosaic patterns are best observed on the younger foliage. Plants may be stunted and fail to produce normal pods.

If the disease attacks plants at the early growth stage, no pods should be expected.

The most common virus disease on cowpeas is cowpea aphid-borne mosaic potyvirus. It is transmitted by aphids.

Mosaic diseases include:

• Cowpea mosaic comovirus (CpMV)
• Blackeye cowpea mosaic potyvirus (BICMV)
• Cowpea severe mosaic virus (CPSMV)
• Cowpea aphid-borne mosaic potyvirus (CAMV)
• Cowpea mottle carmovirus (CPMoV)
• Cowpea golden mosaic bigeminivirus

What to do:

• Plant resistant varieties, where available.
• Use healthy, disease-free seeds rather than saving seed from a crop that could be infected.
• Practise crop rotation with non-legumes (e.g. cereals).
• Remove alternative hosts of virus diseases (legumes).