Crop Pests and Diseases

Introduction

In the Junior School CBC (KICD), Grade 9 Agriculture teaches learners to protect crops. A pest is any organism that damages crops, while a disease is caused by microorganisms such as fungi, bacteria and viruses.

Common crop pests

Common diseases

• Maize streak - virus, spread by leafhoppers.
• Late blight - fungus on potatoes and tomatoes.
• Bacterial wilt - bacteria in tomatoes and potatoes.
• Coffee berry disease - fungus.
• Rust - fungus on beans and wheat.

Control methods

1. Cultural: crop rotation, clean seed, early planting, weeding, removing infected plants.
2. Biological: using natural enemies, such as ladybirds eating aphids.
3. Chemical: pesticides and fungicides, used carefully.
4. Physical/mechanical: handpicking, traps, burning residues.
5. Resistant varieties: tolerant seeds.

Integrated pest management

Combining several methods lowers cost and harm to the environment.

Safety with chemicals

• Wear protective clothing and a mask.
• Follow label dosages.
• Do not spray in windy conditions.
• Keep chemicals away from children and food, and obey the pre-harvest interval.

Worked example

A farmer finds holes in maize leaves and caterpillars inside whorls. The pest is likely armyworm. Control: scout fields often, handpick on small plots, apply a recommended pesticide only if the infestation is heavy, and rotate crops next season.

Try it

• Match each pest to the crop it harms.
• List three cultural control methods.
• Explain why pesticide labels must be followed.
• Scout a school garden and record any pests.