WEEK 2: PEST AND DISEASES OF CROPS

TOPIC: Pest and disease of crops
MAIN AIM: To help the learners know about pest and disease of crops
SUSIDIARY AIM: By the end of the lesson, learner should be able to;

1. Define pest.
2. Classify pests based on the parts of crops they attack and their animal types.
3. Explain the life cycles of some pests.
4. Discuss methods of pest control.

PERSONAL AIM: To keep strictly to time allotted to  each stage of the lesson
PREVIOUS KNOWLEDGE: The learners know about pest from experience
TEACHING AIDS: Research work from the internet, pictures
PROCEDURE: The teacher present the lesson with the following steps
STEP ONE: PEST

 A pest can be defined as any animal (or plant) which causes damage to crops or livestock thereby reducing their yields and economic values. Pests are living organisms which may bite, destroy food crops, damage property or otherwise make lives more difficult.

STEP TWO: Classification of Pests
Pests can be classified based on;

1. The part of crops/plants they attack
2. The type of animal

Base on the part of plants they attack, pests can be classified as;d

1. Leaf feeders
2. Root feeders
3. Stem borers
4. Young shoot feeders
5. Fruit and seed eaters
6. Pests of stored grains

Leaf feeders: These are pests that feed mainly on the leaves of plants. They are referred to as defoliators because they cause the removal of leaves (foliage) of crops, a process known as defoliation. Pests that feed on the leaves of plants are mostly insects such as grasshoppers, beetles, pecan leaf case bearer, moth caterpillar, butterfly caterpillar, sawfly larva, etc. 

Root feeders:  Some pests feed on the roots of crops/plants. These pests live mostly inside the soil. They either prune off roots below the surface or suck root fluids which make them wilt or stunt the growth of the crop.  Examples of root feeders are beetles, gnats, grubs, meadow mice, root-knot nematodes, etc.
Stem borers:  These are mostly insects that attack the stems of plants/crops.  These insects bore or make holes in the stem of crops and feed on the vascular tissues.Examples of boring insects are maize weevils, moths, etc.

Young shoot feeders:  Some pests feed on young shoots of some crops. The pests pierce into the shoots and suck juices from the shoots. Examples of young shoot feeders include water flies, aphids, rabbits, slugs, mice, etc.
Fruit and seed eaters: A wide variety of pests feed on the fruits and seeds of different plants. Examples include cotton stainer, weevils, fruit flies, etc.
Pests of stored grains: Some pests, both insect pests and rodents infest harvested or stored crops especially cereal grains such as rice, wheat, sorghum, millet, and other crops crops like groundnut and beans. Insect pests involved are weevils, beetles, moths while rodents include rats, rabbits, etc.
Based on the type of animal, pests are classified into two

1. Invertebrate pests
2. Vertebrate pests

Invertebrate pests are pests that do not have backbone.  Examples of invertebrate pests are grasshopper, cotton boll weevil, fruit flies, beetles, ticks, caterpillars, crickets, termites, wood ants, etc.
Vertebrate pests are animal pests that possess backbones. They include mammals such as rats, rabbits, grass cutters, pigs, monkeys, squirrels, deer and birds such as guinea fowl, weaver birds, pigeon, quell, etc.
 

STEP THREE: Life Cycles of Some Pests
Life Cycle of beetle
Beetles under complete metamorphosis which means that they pass through four stages of development i.e. Egg→larva→pupa→adult (imago).
Egg stage: The life cycle of beetle begins with the female beetle laying hundreds of tiny, oval, white or yellow eggs usually on a leaf, in the soil or in rotten wood depending on the species involved.  It usually takes 4-19 days for the eggs to hatch into the larval stage.
Larval stage: The larva of beetle is called grub. The larva eats tremendous amount of food and continues to grow, shedding its exoskeleton many times while it grows. This process of removing the exoskeleton is known as ecdysis or moulting.
Pupa stage: This is the resting stage where gradual transformation into the adult stage takes place. The pupa does not move about and seems to be inactive. The pupa stage usually occurs during winter and can last for about 9 months. After pupating, an adult beetle emerges.
Adult beetle: Adult beetle feeds, move about and mate with the opposite. After mating, the female beetle lays eggs for the beginning of another generation.

 
LIFE CYCLE OF BEETLE

Life Cycle of Grasshopper

Grasshopper undergoes incomplete metamorphosis which involves three major stages—the eggs, nymphs and adults. The male and female grasshoppers mate for fertilization to take place.
Egg stage: The female grasshopper lays fertilized eggs either underneath the sand (about 1-2 inch depth) or among leaf litters. There are usually more than 10 egg pods, each of which contains about 10- 200 rice shaped eggs. The eggs remain dormant for months (about 10 months) especially during winter. When the weather becomes warm, the eggs hatch into nymphs.
Nymph stage:  The nymphs feed on soft and succulent plant foliage. Nymphs are miniature versions of adult grasshoppers except they are light in colour, smaller in size and wingless. Nymphs undergo 3-6 moults and change their forms before becoming adults. As they moult, they increase in size and wing pads gradually develop on the thorax part of the body. After about 25-30 days, the wings develop completely and they become adults.
Adult stage:  This is the final stage of development. At this stage, the grasshopper gain sexual maturity after about 15 days and the cycle continues.
 

STEP FOUR: Control of Pests
Pests of crops can be controlled through the following methods;

1. Physical method
2. Cultural method
3. Chemical method
4. Biological method

Physical method: This involves the removal of pests by hand-picking of insects and their larvae, setting traps or sticky boards to catch rodents, shooting rodents with gun, fencing round the farm with wire nets.
Cultural method: This method involves the use of farm practices to prevent or control pests especially on the field.  Some cultural method strategies include crop rotation, mixed cropping, early planting, regular weeding, use of resistant varieties,etc.
Chemical method: This involves the use of chemicals to eliminate or control pest population. These chemicals can be in form of powder, liquid, granules and emulsions. Examples of chemicals used are
Pesticides- chemicals used to control pests
Avicides—chemicals used to control birds
Rodenticides-chemicals used to control rodents
Nematicides—used to control nematodes
Insecticides—used to control insects
Biological method: Biological control involves the introduction of the natural enemies of the pests to control or keep the pest population under control. Such enemies eat up the pests thereby reducing their populations.
EVALUATION:

1. Define pest.
2. Classify pests based on the parts of crops they attack and their animal types.
3. Explain the life cycles of some pests.
4. Discuss methods of pest control.

CONCLUSION: The teacher concludes the lesson by summarizing the topic from the begining and give assignment to the learner.
ASSIGNMENT:

1. Define pest.
2. Classify pests based on the parts of crops they attack and their animal types.