Pest and disease management

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Pest and disease management is crucial for obtaining higher marketable bulb yield and good quality bulbs.

• INSECTS  Thrips (Thrips tabaci):symptoms 1. Thrips infestation at an early stage (transplanting to 45 days) can be identified by curling and twisting of leaves. 2. Typical symptom is the presence of white or silvery patches on the leaves. 3. In severe infestation, whole plant looks blemished and turns white.:Control measures:1. Planting of two rows of maize or one outer row of maize and an inner row of wheat as a barrier crop surrounding garlic crop (250 sq. m) at least 30 days prior to planting of garlic helps to block the movement of adult thrips.  2. Spray insecticides Profenofos (0.1%), Carbosulfan (0.2%) or Fipronil (0.1%) when thrips population crosses the economic threshold level of 30 thrips/plant.control measures:

• Eriophyid mite (Aceria tulipae):Symptoms1. Leaves do not open completely. Whole plant shows stunting, twisting, curling and yellow mottling.  2. Mottling is seen mostly on the edges of the leaves.Control measures:Spray Dicofol (0.2%) or sulphur (0.05%) as soon as the symptoms appear. Repeat the spray after 15 days, if necessary.

• Red spider mite (Tetranychus urticae):Symptoms.1. White discoloration of leaves with small patches of faeces, eggs, larvae and adult mites.2. Yellow or bronze spots on the leaves. 3. Spider webbing on leaves.Control measures:Spray Dicofol (0.2%) or sulphur (0.05%) as soon as the symptoms appear. Repeat the spray after 15 days, if necessary.:

• NEMATODE

• Stem and bulb nematode (Ditylenchus dipsaci)Symptoms1. D. dipsaci enters through stoma or plant wounds and create galls or malformations in plant growth. This allows for the entrance of secondary pathogens like fungi and bacteria. 2. Symptoms are stunted growth, discoloration of bulbs, and swollen stems.Control measures:1. Bulbs that show signs of disease should not be planted 2. Proper sanitation of fields and tools is essential because this nematode can survive and reproduce in infected plants and residues.

• FUNGAL DISEASE

• Purple bloch (Alternaria porri)1. Initially small, elliptical lesions or spots on leaves that often turn purplish-brown and are surrounded by chlorotic margin.2. If the spots enlarge, chlorotic margin extend above and below the actual lesion. Lesions usually girdle leaves, causing them to fall over. Lesions may also start at the tips of older leaves.Control measures:Spay Mancozeb @ 0.25% or Tricyclazole @ 0.1% or Hexaconazole @ 0.1% or Propiconazole @ 0.1% at 10-15 days intervals from 30 days after planting or as soon as disease appears

• White rot (Sclerotium cepivorum)1. Yellowing and dying back of leaf tips.2. Roots are normally destroyed. Superficial white fluffy mycelium may be present on decaying scales. 3. Brown or black sclerotia develop on surface or within tissue.Control measures1. Crop rotation should be followed, infected plant may be destroyed and the soil around these plants should be treated.  2. Soil solarization at high temperature reduces the disease incidence. 3. Carbendazim @ 0.1% may be applied.:

• STORAGE DISEASE

• Black mould (Aspergillus spp.)Symptoms:1. Bulbs show black discoloration at the neck and streaks of black mycelium and conidia beneath the outer dry scales.2. In advanced stages all scales are infected and the bulb shrivels.Control measures1. After proper drying, store bulbs in dry conditions.  2. Avoid bruising when bulbs are harvested, stored or transported.

• Bacterial rot (Erwinia spp. and Pseudomonas spp.)Symptoms:Watery, foul-smelling fluid squeezes from the neck of diseased bulbs when pressed.Control measures:1. Proper curing after harvest  2. Store bulbs in dry conditions with good ventilation

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.