Page 33 - Agriculture_Form_3

Agriculture for Secondary Schools

Stalk/stem borers: Stalk/stem borers are pests that cause great yield losses in
maize by boring into the stems. This results in ‘dead heart’, stunted growth, weak
plants, as well as poor grain development on cobs. Effective management includes
early planting to avoid peak infestations and the use of resistant maize varieties.
In severe cases, chemical insecticides should be applied early after consulting the
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agricultural extension worker. Figure 2.4 shows the maize stem borer larva and
the damage it causes.

Figure 2.4: Stalk/stem borers and the damage they cause

Fall armyworm: The fall armyworm is a destructive pest that feeds on maize
leaves, causing irregular holes and skeletonised foliage. In severe cases, it can
lead to complete defoliation and poor grain formation. Larvae also damage
maize cobs. To identify their presence, you will see the frass near feeding
sites. Management includes early detection and regular monitoring, along with
biological control using Bacillus thuringiensis (Bt) or natural predators like
lacewings and lady beetles. In severe cases, insecticides are used. Figure 2.5
shows the fall armyworm and the damaged maize leaves.

Figure 2.5: Fall armyworm and damaged maize leaves

24 Student’s Book Form Three

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AGRICULTURE F3.indd 24 17/09/2025 14:11