Kiserian,Kenya
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July 25, 2023
Farmers Pest and Diseases

Common Pests and Diseases in Onion


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  • DISEASE.

     Here are some of the common Diseases and their symptoms and how to control them:

    Fungal Black mold Aspergillus niger:

    Symptoms.

    Post-harvest black discoloration at neck; lesions on outer scales; black streaks under outer dry scales; entire surface of bulb turning black and shriveling.

    Management:

    Treat seeds with appropriate fungicide prior to planting to reduce rot in mature bulbs; avoid bruising bulbs during and after harvest; storing at temperatures below 15°C (59°F) prevents mold from spreading but it will resume once temperature increases
  • Botrytis leaf blight Botrytis squamosa.

    Symptoms.

    Small white lesions with light green halos which may expand slightly as they age; in prolonged periods of moisture fungus may develop rapidly and cause leaf blighting

    Management.

    Plant onions in single rows allowing at least 30 cm between plants to promote good air circulation and quick drying of foliage after rain; time irrigation to allow plants time to dry out sufficiently; apply appropriate fungicide sprays when plants have at least five true leaves and early symptoms of disease
  • Downy mildew Peronospora destructor.

    Symptoms:

    Pale spots or elongated patches on leaves; gray-purple fuzzy growth on leaf surface; leaves turning pale then yellow; leaf tips collapsing.

    Management.

    Avoid planting infected sets; rotate crops to non-allium species for 3-4 years; plant in well-draining areas and do not overcrowd plants; destroy all infected crop debris; apply appropriate foliar fungicides taking care to apply thoroughly to waxy leaves
  • PESTS.
  • Mites 

    Bulb mites Rhizoglyphus spp. Tyrophagus spp.

    Symptoms:

    Stunted plant growth; reduced stand; bulbs rotting in ground or in storage; pest is a cream-white, bulbous mite <1 mm in length, which resembles a pearl with legs.

    Management:

    Do not plant successive crops of onion or garlic in same location; allow field to fallow to ensure that any residual organic matter decomposes completely - crop residues can harbor mite populations; treating garlic seed cloves with hot water prior to planting may help reduce mite populations
  • INSECTS
  • Leafminers Lyriomyza spp:

    Symptoms:

    Thin, white, winding trails on leaves; heavy mining can result in white blotches on leaves and leaves dropping from the plant prematurely; early infestation can cause yield to be reduced; adult leafminer is a small black and yellow fly which lays its eggs in the leaf; larave hatch and feed on leaf interior.

    Management.

    Check transplants for signs of leafminer damage prior to planting; remove plants from soil immediately after harvest; only use insecticides when leafminer damage has been identified as unnecessary spraying will also reduce populations of their natural enemies
  • THRIPS

    (Onion thrips, Western flower thrips) Thrips tabaci Frankliniella occidentalis

    Symptoms.

    Discolored, distorted tissue; scarring of leaves; severly infected plants may have a silvery appearance

    Management.

    Natural enemies include some species of predatory mite, pirate bugs and lacewings; avoid planting onion in close proximity to grain fields as thrips populations build up on these plant in the spring; overhead irrigation of plants may help reduce thrips numbers; apply appropriate insecticides at first sign of thrips damage


The most effective way of managing Pests and Diseases is religiously following a spray and feeding regime. Onion Doctor curates spray and feeding programes at competitive prices. Be sure to contact us for a quote.


Onion Doctor supports small holder farmers across Africa with quality and affordable Onion and Garlic seedlings, Onion seedlings, Farm planning services, Soil testing, Drip irrigation installation and maintenance, Agronomic support, Onion and Garlic value pack, Farm management, E-extension and on-farm training for farmers to optimize on yields and get maximum profits.

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