This covers the various pests and diseases that are of economic importance when growing maize in Kenya. We Identify and define the methods of management of these pests and diseases.

Pests

Pest types vary, ranging from; insect pests, animal pests, weeds, pathogens and human pests. Common pests that affect maize plants include:

1) Fall Army Worm

The Fall armyworm is a migratory insect pest, native to America, with moth as adult stage and larvae (caterpillars) as the destructive phase which causes severe foliar and cob damage in maize and other cereal crops.

Symptoms

• Seeing the pest itself
• Observing symptoms and signs:
  Window pane-like damages, initially appearing as “scratch” on the leaf, large ragged and elongated holes on leaves, frass (excreta) or sawdust-like substance or granular (pellet-like) substance on leaves.

Management and Recommendation

• Ensure you plant early in the season.
• Look to avoid late and off-season planting.
• Use mechanical control methods such as collection and destruction of egg masses and young larvae, application of sawdust or sand into the whorls which leads to the aberration and desiccation of the young larvae, use of traps, bird perches can also be used.
• Use of insecticides.
• Restrict or prevent movement of infested plant materials.
• Report attack to nearest KALRO station and agricultural extension office

2) Maize Stalk Borer/ Stem borer

Symptoms

• The presence of boring on the stem.
• Internal feeding when you look inside the stem.
• Wilting and/or dying of the upper leaves or by ragged irregular holes chewed in the newly unrolled leaves.
• The characteristic “dead heart” is caused by the insect boring into the stalk at the soil level and tunnelling upward.

Management and Recommendation

• Intercropping with non-host crops like cassava.
• Use border crops like nappier grass (push-pull method).
• Use of chemicals to control infestation.

Other pests such as chaffer grubs and termites can be controlled by dressing seeds with the recommended chemical.

Birds and rodents

These can be controlled by trapping, scaring and use of rodenticide

Diseases in Maize Plants

1) Maize Lethal Necrosis (MLN)

Symptoms

• It is characterized by a black sooty substance at the flowering point (head) or the ear where the cobs form.
• Dying leaves, lead to premature plant death.
• Failure to tassel and sterility in male plants
• Malformed or no ears
• Presence of rotting cob

Management and Recommendation

• Use of hybrids that are resistant to MLN.
• Uprooting and removing affected plants.
• Use of crop rotation or growing alternative crops
• Be aware of the specific season and planting time to avoid the spreading of the disease.
• Apply good agronomic practices.
• Chemical spraying of vectors of the disease.
  NB/: If a plant with smut or Maize Lethal Necrosis (MLN) is noticed in the field, it should be uprooted and destroyed by burning since the disease is infectious. Do not bury or feed the plant with smut to livestock as this would further spread the disease.

2) Grey Leaf Spot (GLS)

GLS is a foliar fungal disease that affects maize. Environmental conditions that best suit infection and growth include moist, humid, and warm climates coupled with poor soil drainage.

Symptoms

• Leaf lesions.
• Discoloration (chlorosis).
• Foliar blight.

Management and Recommendation

• Use of crop rotation.
• Proper residue management.
• Use of fungicides.
• Proper weed control.
• Planting of GLS-resistant maize varieties developed by KALRO such as KH600-14E, KH600-15A, KH600-16A and KH600-18A.

3) Maize Mosaic Virus

Symptoms

• The virus causes a white to yellowish streaking on the leaves.
• The streaks are very narrow, more or less broken and run parallel along with the leaves.
• Eventually, the leaves turn yellow with long lines of green patches

Management and Recommendations

• Use certified disease-free seed
• Planting a large area of maize all at once
• Inspect the field regularly when the maize is small, looking for diseased plants
• Uproot infected plants when they first show signs of disease.
• Remove infected maize plants (roguing) at an early stage
• Keep the fields free from weeds,
• Remove cereal crop residues from the field.
• Use chemical insecticides.

4) Northern Corn Blight (Turcicum Leaf Blight)

Symptoms

• Cigar-shaped or necrotic grey-green lesions on the leaves range from one to seven inches long.
• Streaks that run parallel to the leaf veins.
• Lesions typically have a sooty appearance during humid weather

Management and Recommendations

• Using hybrid seeds that are resistant.
• Reducing the amount of infected residue left in a field
• Managing weeds to improve airflow and reduce humidity
• Encouraging residue decomposition with tillage
• Use of foliar fungicides

5) Common rust

Symptoms

• Abnormal outgrowths of maize leaf tissues

Management and Recommendations

• Use of resistant varieties
• Use of fungicides
• Remove and destroy all farm debris after harvest
• Practising crop rotation
• Burning of infected plant parts

6) Common Smut of Maize (Ustilago maidis)

Symptoms

• Fungus forms galls/swellings on all above-ground parts of maize species
• Ears produce mushroom-like tumours or galls

Management and Recommendations

• Use of resistant varieties
• Use of fungicides
• Remove and destroy all farm debris after harvest
• Crop rotation
• Burning of infected plant parts

7) Head Smut (Sphacelotheca reiliana)

Symptoms

• Abnormal development of the tassels/leaves
• Black fungal spores or malformed and overgrown black masses of spores that develop inside individual male florets
• Masses of black spores in place of the normal ear leaving the vascular bundles exposed and shredded
• Twisting and distortion
• Abnormal leaves, colours and fungal growth
• Empty grains, galls, rots
• Mould growth on seed and dwarfing of the whole plant

Management and Recommendations

• Use of resistant hybrids
• Cultural control and field sanitary methods
• Seed treatment of maize
• Frequent irrigation after planting reduces the incidence
• Application of organic amendments where applicable

8) Maize Ear Rot

Symptoms

• Early infected plants have a yellowish-brown colour, a golden-brown-spot on husks/ears or bleached husks/ears
• Husks on severely infected plants dry down well before the rest of the plant
• White fungal mycelia occur upon infection from the base of the ear to the tip.

Management and Recommendations

• Use of resistant hybrids
• Crop rotation
• The burning of crop residues reduces the infections

Read our Complete Guide on How To do Maize Farming in Different Regions of Kenya