Pests and Diseases of Crop Plants

Back to: Basic Science Primary 4

 

Welcome to class! 

In today’s class, we will be talking about the pests and diseases of crop plants. Enjoy the class!

Pests and Diseases of Crop Plants

Introduction

Crop plants are plants that are grown by humans for food and other resources. Grains, vegetables, and fruits are some of the crops that can be classified as crop plants.

In this lesson, we will learn some pest and diseases that can affect these crop plants.

Meaning of concepts

A pest is any organism that spreads disease, causes destruction or is otherwise a nuisance. Pest: It is an organism that causes any type of damage to the crop plants.

A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism.

Common pest of plants

Common pest of crop plants are:

1. Insects:  Insects are responsible for two major kinds of damage to growing crops. First, it directs injury done to the plant by the feeding insect, which eats leaves or burrows in stems, fruit, or roots. The second type is indirect damage in which the insect itself does little or no harm but transmits a bacterial, viral, or fungal infection into a crop.
2. Bats: Birds attack the crop plants and eat grains. Crow, Parrots and Sparrows are major among birds that attack the crops.
3. Rodents: They consume and damage human foods in the field and stores. Also, they spoil it in stores by urine and droppings reducing the sales value.
4. Monkeys: Monkeys are a major agricultural pest. Monkey habitat often lies within a short distance from fields and villages.

Evaluation

1. What are pests?
2. What are diseases?
3. List four types of common crop pest you know.

Causal agents of diseases

The term disease causative agent usually refers to the biological pathogen that causes a disease, such as a virus, parasite, fungus, or bacterium.

These causative agents are transmitted from organism to organism where they cause the organism either plant or animal to fall sick.

 Common crop diseases

1. Cassava mosaic: An infected leaf has white or pale-yellow or pale-green spots. It is often twisted, distorted, and stunted
2. Yellow rust: A fungal disease of wheat.
3. Rice bacterial blight.
4. Corn Smut
5. Blossom End Rot
6. Crown Gall
7. Downy Mildew
8. Early blight
9. Fire Blight
10. Late blight
11. Leaf spot

Controlling pest and diseases of crops

The cultural method includes:

1. Selecting areas unfavourable to fungi and bacteria.
2. Choosing the right time to sow
3. Selecting healthy and disease-free seeds
4. Crop rotation is essential for controlling soil-borne diseases

The chemical method includes:

1. Seed treatment with fungicide before transplanting
2. The soil too is treated with some chemicals

Effects of using chemicals in controlling diseases

1. Some pesticides do not break down easily.
2. There could be an accumulation of the substances in the tissues of plants
3. The substances accumulated are transferred to other organisms as they eat the food.
4. The pesticides upset the ecosystem
5. The pesticides accumulating in the soul may kill useful decomposers in the soil.

Evaluation

1. Mention chemical and cultural ways of controlling diseases of the crop.
2. List five common plant diseases.

Assignment

1. Explain any physical method of controlling crop diseases.

 

In our next class, we will be talking about Water Evaporation and Condensation.  We hope you enjoyed the class.

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