Page 85 - Agriculture_Form_3

Agriculture for Secondary Schools

protect the crop. Good disease management increases yield and bean quality.
Some of the common diseases are described in the following sub-sections.
Angular leaf spot: This is a fungal disease which affects leaves. It forms brown,
square-like spots that reduce leaf health. When severe, the disease causes early
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leaf fall and low yield. Removing infected leaves helps to minimise disease
spread. Practising crop rotation helps to break the disease cycle. Resistant bean
varieties should be planted to reduce future infections. Figure 5.4 (a) shows
symptoms of angular leaf spot in beans.

Figure 5.4 (a): Symptoms of angular leaf spot in the common bean leaf and pods

Rust: This is a fungal disease that produces orange-brown spots on leaves (Figure
5.4 (b)). The spots look like small, raised bumps on leaf surfaces. Rust weakens
the plant and lowers pod production. Using resistant varieties is a simple and
effective solution. Using resistant varieties and avoiding excessive application
of nitrogenous fertilisers reduces disease risk. Additionally, recommended
fungicides may be used under the supervision of crop extension officers.

Figure 5.4 (b): Symptoms of rust in bean leaves
Root rot: This disease is caused by fungi that live in wet soils (Figure 5.4 (c)).
It makes bean roots rot and turn brown or black. Bean plants with root rot wilt
may die early. Sowing beans in well-drained soils helps to reduce root rot cases,

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