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BRE 211: Principles of Agriculture and Forestry


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Title: BRE 211: Principles of Agriculture and Forestry

BRE 211 Principles of Agriculture and Forestry
  • Lecture 4

Principles of Agricultural/ Crop Production
  • They include
  • Land preparation
  • Plant propagation
  • Nursery establishment
  • Transplanting seedlings
  • Field Planting
  • Fertilizer application
  • Crop protection
  • Harvesting
  • Post harvest handling and storage

Land Preparation
  • Involves
  • Land Clearing
  • Drainage
  • Preparatory cultivation
  • Land Clearing
  • Existing vegetation is cleared.
  • Intensity of clearing varying from clear felling
    to selective thinning depending on the crops to
    be grown.
  • Intensively grown crops usually require total
    clearance of the vegetation.

Techniques of Land Clearing
  • Normally two techniques including
  • Slash and Burn
  • Clear Felling and Stumping
  • Slash-and-burn involves
  • Slashing the herbaceous undergrowth followed by
    burning of the debris and standing shrubs and
  • In some instances the bigger trees are pruned or
    ring barked and fired to kill them in places
    where they endanger the growing crops.

Advantages of Burning
  • Releases nutrients bound in the plant tissues in
    readily soluble ash and the planted crop may
    subsist on such nutrients immediately on
  • Acts as a disinfectant that destroys pests,
    disease causing organisms and weed seeds.

Disadvantages of Burning
  • Destroys the potential organic matter in
    vegetation by releasing the volatile nutrients
    such as nitrogen and sulphur.
  • Some forest litter may resist burning thus result
    in poor land clearing.
  • However,
  • Burning is becoming less frequent on intensively
    farmed areas near homes and villages.
  • Burning of clearings is still practiced in the
    establishment of tree crops.
  • Clear felling and stumping
  • This is rare but under intensive or mechanized
    cropping it is done thoroughly in order to
    facilitate mechanical cultivation.
  • After clearing, soil conservation and drainage
    works commence.

  • Causes of Poor drainage
  • Some soils have a water table permanently or
    seasonally high enough to adversely affect crop
    growth thus need drains to lower the water table.
  • Physical condition of one or more horizons of the
    soil checks the downward movement of excess
    surface water thus impeding the drainage of
    excess surface water to a depth below the root
    range of crops.
  • If the soil is wet and especially if it is high
    in clay content, a barrier impeding water
    percolation can also be formed by the smearing
    action of tractor wheel slip or of an implement
    which destroys structure and seals coarse pores
    and cracks.

Conditions for Drainage
  • Where rainfall in abundant and well distributed
    throughout the year, it might be desirable to
    keep the water table below crop rooting depth at
    all times.
  • Although it is necessary to improve drainage
    during part of the wet season in drier areas, it
    is undesirable to lower the water table more than
    is necessary since in such areas the objective is
    to conserve water.
  • On peat soils, it is usually desirable to
    maintain the water table as high as crop
    requirements permit because draining peat too
    deeply enhances its tendency to dry, shrink and
    reach a high temperature during the day.

Conditions for Drainage
  • Tree crops that need to develop a deep root
    system to anchor them firmly against strong winds
    will require a lower water table than some annual
    crops or surface-rooting perennials such as
  • Main effect of improving drainage is to improve
    the aeration of the soil enabling the crop to
    develop a deeper root system so that it can tap a
    larger volume of soil for nutrients and is better
    able to withstand periods of draught

Methods of improving drainage
  • Sub-surface drains of tile, plastic pipe, rubble
    (bits of broken stone) and brushwood. Uncommon
    due to initial and maintenance cost
  • Open surface drains Made mechanically with
    scrapers, bulldozers, and drainage ploughs or
    dragline excavators. Cheaper in cost but take up
    land, inconveniences mechanized tillage
    operations, harbour obnoxious weeds and rodents
    requiring constant maintenance.
  • Ridge and furrow system Land is formed into
    broad ridges with a slight gradient on the
    furrows or ditches between them.
  • Cambered bed system This is a modification of
    the ridge and furrow system in which the land is
    raised into beds.

  • Drains cannot help once the structure of the
    surface soil has been destroyed
  • They only reduce the risk of such damage
    occurring by keeping the surface layer drier and
    thus prolonging periods during which it is not
    too wet for mechanized tillage.

Preparatory Cultivation
  • It is better to cultivate at the end of the rains
    in order to expose weed seeds, pests and
    pathogens to desiccation during the dry season.
  • Extent and efficiency of preparatory cultivation
    depends on the type of soil and the cultivation
  • Simple and light tools such as the hoe, panga,
    slasher, etc are associated with cultivation of
    soils in small-scale tropical agriculture.
  • Human supplies the energy used in cultivation
    although farmers in the savanna also commonly use
    animal power.
  • Tractors and their associated implements such as
    ploughs, harrows, and ridges are associated with
    highly developed agriculture of industrialized
    countries .

Effects of Cultivation
  • Eliminates competition by weed species.
  • Incorporates organic and inorganic manure.
  • Improves the tilth or granular condition of the
    soil, which facilitates aeration, water
    percolation and easy rooting of seedlings.
  • Helps destroy some pests and pathogens present in
    the soil by exposing them to the sun.
  • Buries some weed seeds too deep for germination.
  • However may turn up previously buried weed seeds
    which can dominate the re-growth after

Plant Propagation
  • Objectives
  • To increase the number of plants
  • To preserve the useful characteristics of the
  • Types
  • Sexual Propagation (Propagation by seed)
  • Asexual Propagation (by use of specialized
    vegetative parts of the plants or by artificial
    techniques such as grafting, layering, cutting or

Propagation by seed
  • Commonest way of propagating self-pollinated and
    many cross-pollinated crops.
  • Advantages
  • Seeds are usually not expensive
  • Seeds can be stored for long periods
  • Seeds can remain viable at least until the next
    planting season when stored in a cool dry place
  • Seed does not usually carry over diseases and
    pests, which attack growing crops although some
    fungal spores infect seeds.

Propagation by seed
  • Disadvantages
  • Development of off-types and variation in plant
    populations when cross-breeds are grown
  • Long juvenile period when plant is unable to
    produce seeds especially in tree crops
  • Some seeds do not produce plants that resemble
    their parent plants
  • Some seeds cannot produce yields during the first
    year e.g. Root and tuber crops.

Vegetative propagation
  • Depends on the ability of plant parts to
    regenerate roots and shoots and grow into new
    plants having the same characteristics as their
    parent plant.
  • Advantages
  • Eliminates the problems of dormancy and reduces
    the juvenile period of plants
  • Yields are obtainable easier and faster than seed
    propagated plants.
  • Produces seedless crops e.g. banana easily
  • Maintains crossbred plants in heterozygous
    condition indefinitely.
  • Disadvantage
  • Danger of transferring diseases to the new plants
    or locations.

Methods of Vegetative Propagation
  • Use of specialized vegetative parts or modified
    stems and roots such as bulb, corm runner,
    rhizome, suckers, tubers and root.
  • Induction of adventitious roots and shoots by
    cutting or layering the stem e.g. in tea and
    sweet potato propagation.
  • Grafting Two plant parts are joined by
    regeneration of their tissues.
  • Budding Only the vegetative bud is joined to
    another plant where it regenerates a new plant.
  • Ratooning Outgrowths from stools of a harvested
    crop are used.

Nursery Establishment
  • A Nursery phase is an important part of the
    planting operation for most trees and some field
  • Seedlings can be better cared for and
    conveniently watered with less effort to increase
    growth and development.
  • Characteristics of a good nursery site
  • Should be near a source of water
  • Should be as near as possible to the site of
    field planting
  • Site should not be subject to planting other
  • Ground should be level or terraced.

Nursery Requirements
  • Water
  • A small nursery can be watered using watering
    cans by family labour while a larger one may
    require more workers or the use of a pump and
    hose system.
  • Polythene bags
  • Most widely used containers for nursery seedlings
    because they are cheap and durable and make
    handling of seedlings at planting very easy.
  • size of bags used depends on the seedlings.
  • Shade
  • Young seedlings do better under partial shade at
    the early stages. they will become self-shading
    when they get larger

Nursery Requirements
  • Fertilizer
  • Usually nursery seedlings will grow faster if
    fertilized. The easiest way to fertilize
    seedlings is to dissolve a nitrogen fertilizer
    containing all the major nutrients in water and
    water lightly once every week.
  • Fertilizer scorch can be avoided by immediately
    re-wetting with water alone.
  • Sometimes micronutrient deficiencies will occur
    and these are best dealt with by watering with a
    complete/compound fertilizer dissolved in water
    and given periodically.

Transplanting seedlings
  • Should be done during a sufficiently wet season.
  • Before planting the seedlings, any weak,
    slow-growing, diseased, deformed or otherwise
    abnormal plants should be discarded as it affects
    the long-term yield of the field planting.
  • Seedlings grown in Polythene bags are easy to
    transport to the field and lorry, tractor,
    trailer or hand may carry them depending on the

Transplanting seedlings
  • Use a box and double poles carried on the
    shoulders of two workers to carry seedlings over
    rough ground.
  • Before planting the Polythene bags must be
    stripped off by slitting lengthwise with a razor
    blade or a very sharp knife.
  • Although Polythene bags are widely used for
    nurseries some farmers may still prefer to plant
    seedlings directly in the soil.
  • This often means that considerable damage is done
    to the seedling on extraction, thus delaying its

Field Planting
  • Seed or planting material largely determines the
    quantity and quality of the harvested produce.
  • Good stocks of planting materials ensure
  • Reduced costs of cleaning, standardization and
  • Uniform germination thus eliminating replanting
    or supplying missing stands
  • Vigorous seedling growth which reduces weed and
    disease damage
  • Uniform growth rates, maturity and produce

Field Planting
  • Low grade or poor-quality planting materials lead
  • Uneven germination and establishment which may
    necessitate replanting or supplying missing
  • Feeble seedling growth susceptible to disease and
    insect damage
  • Costly disinfection or grading of planting
    materials against seed-borne diseases and pests
  • Uneven growth rates due to lack of uniformity in
    genetic composition.
  • Uneven maturity which affects the cost and
    efficiency of harvesting
  • Lack of uniform produce due to a combination of
    all the above factors.

Field Planting
  • This affects not only the efficiency of primary
    processing but also the quality and market value
    of the products.
  • Most farmers in the tropics still provide for
    their planting materials from their own harvests
    or purchase them from unregulated markets.

Methods of planting
  • Broadcast
  • This is limited to crops that will be
    transplanted particularly small seed crops. It is
    unsuitable for large seeds and vegetative
  • Drilling
  • This is planting seed in small furrows
  • Dibbling
  • Holes are made and the seeds placed in these
    holes and covered. The crops could be planted in
    scattered like beans.

Sowing Practices
  • The successful establishment of seedlings of
    annual crops depends upon
  • Viable seed of adapted cultivar
  • Uniform sowing placement depth
  • Firm seed-soil contact
  • Availability of moisture and nutrients in the
  • The factors involved in sowing management can be
    divided into two broad groups
  • Mechanical factors such as depth of planting,
    emergence habit, seed size, seedbed texture, and
    seed-soil contact.
  • Biological factors such as companion crops (in
    mixed cropping and pastures) and competition for

Spacing and plant population
  • Spacing crops optimally reduces interplant
    competition for sunlight, moisture, air and
  • The ultimate yield from a unit land area is
    contributed to by all the plants growing on it.
  • Excessively wide or narrow spacing leads to
    reduction in yield.
  • The exact spacing for any crop depends on
  • Soil productivity
  • Location
  • Time of planting.
  • On fertile moist soils, closer spacing will give
    better results than on poor soils or soils
    susceptible to moisture stress.
  • This explains the sustained high yields from
    close spacing and high plant populations in
    irrigated as compared to rainfed crops.

Fertilizer Application
  • Fertilizers are chemical compounds containing the
    elements that are added to the soil to supplement
    its natural fertility.
  • Fertilizers containing only one of the major
    elements (N, P, and K) are single, simple or
    straight fertilizers
  • Those containing two or three elements are
    classified as mixed compound or complex

Fertilizer Application
  • Nutrients in fertilizers must come within the
    feeding range of plants roots for maximum
    benefit from the application.
  • The soluble constituents of fertilizers diffuse
    through the soil vertically and only slightly in
    a lateral direction.
  • The method of application therefore must ensure
    distribution in a moist soil to reach the plant
  • Thus method of applying fertilizer is important.

Methods of Fertilizer Application
  • Broadcast before planting Fertilizer is spread
    as uniformly as possible over the field after
    ploughing land then mix it with soil by ploughs
    or cultivators.
  • Gives good results with crops like millet which
    are planted in narrow rows.
  • Suitable for those crops whose seeds are usually
  • However, it stimulates weeds.
  • Row Placement Fertilizer is placed in bands or
    in localized areas along rows at a calculated
    distance for maximum absorption by the plants.
  • Advantages
  • Fertilizer comes in contact with minimum amounts
    of soil particles reducing phosphorus fixation.
  • Fertilizer is within reach of the roots and the
    plant can feed on it easily
  • Fertilizer placed in bands does not supply
    nutrients to the weeds near the surface

Methods of Fertilizer Application
  • Top-dressing Second application by broadcasting
    on the soil surface close to the plants when the
    crop is 3-4 weeks old.
  • Drill placement Fertilizer is applied along
    with the seed.
  • Good for crops like wheat, maize and other
    cereals, which can withstand contact with the
  • Band Placement Fertilizer is placed in bands on
    one side or both sides of the row about 5cm below
    the seed and 4cm away from the seed or plant.
  • The method is useful for cotton, tomato and
    potato crops that are sensitive to direct contact
    with fertilizer.
  • Side-dressing Second application when the crop
    is partly grown (4-8 weeks) given as a continuous
    band near the crop row to a depth of 4-5 cm.

Methods of Fertilizer Application
  • Application by plough Fertilizer is placed in a
    continuous band at the bottom of the plough
    furrow. Each band is covered as the succeeding
    furrows are turned over.
  • Applying liquid fertilizer Fertilizer is mixed
    with most fungicides and pesticides and applied
    simultaneously or dissolved in irrigation water
    and applied together in a process referred to as
  • Used for high-value crops by direct spraying.
  • Carbamide (urea) is the most commonly used in
    this way.

Types of Fertilizers
  • Nitrogenous fertilizers
  • Phosphatic fertilizers
  • Potassium fertilizers
  • Mixed or compound fertilizers.
  • Farmyard manure

Nitrogenous Fertilizers
  • All major inorganic fertilizers in common use are
    synthetically produced.
  • Many nitrogenous compounds are made from ammonia
    in an atmospheric nitrogen manufacturing process
    known as the harber process.
  • Hydrogen is combined with nitrogen in the ratio
    31 by volume at high temperature (400-500 o C)
    and pressure (200-1000 atmosphere) in the
    presence of catalyst form ammonia.
  • This ammonia is used directly as fertilizers or
    is converted into various nitrogen fertilizers.

Phosphatic fertilizers
  • Are of three grades depending on their
  • Water-soluble phosphate
  • Citrate-soluble phosphate
  • Phosphates that are only soluble in strong
    mineral acids such as sulphuric acid and nitric
  • The solubility depends on the chemical
    composition or formula of the phosphate and the
    degree of fineness.

Potassium Fertilizers
  • Manufactured from natural deposits of potassium
    salts found in various parts of the world.
  • The crude potash minerals are dissolved in water
    and the various salts separated by fractional
  • All are soluble in water and the potassium
    content is readily available to plants unlike the
    nitrogen fertilizers.
  • Most potash fertilizers have no effect on soil
  • Most important potash fertilizer materials are
  • Muriate of potash
  • Sulphate of potash

Mixed or compound fertilizers
  • Contain at least two of the three major elements
    N, P, K.
  • Advantages of compound fertilizers include
  • Can be applied by hand as well as a fertilizer
    drill since it is usually dry with fine and
    well-mixed granules.
  • Is stable and does not cake up, form lumps or
    deteriorate in any way over time.
  • Contains all the major plant nutrients in the
    right proportions.
  • The ready-made mixture saves farmers the labour
    of mixing fertilizers.
  • Save time and labour when applied in the
    calculated amount instead of using separate
    straight fertilizers.
  • Disadvantages include
  • Cost slightly more than the total cost of three
    equivalents of NPK.
  • May be unsuitable for many soils.

Farmyard Manure (FYM)
  • FYM refers to all the refuse from farm animals.
  • It is a by-product consisting of two components
    solid and liquid in a ratio of 31.
  • Solid part is made up of dung and straw that has
    been used for animal bedding while the liquid
    comes from the urine.
  • Dung comes mostly from undigested material and
    the urine from the digested material that is
    absorbed by the animal and then excreted.
  • More than 50 of the organic matter contained in
    dung is in the form lignin and protein similar to
    those contained in humus.
  • This material is quite resistant to further decay
    and therefore the nutrients present in this
    fraction of dung are liberated very slowly.
  • Nutrients present in the urine are readily
    available either directly or after simple
  • Over half of nitrogen, almost all the phosphate
    and about two fifths of potash are found in the
    solid portion.

Farmyard Manure (FYM)
  • Manure is essentially a nitrogen-potash
  • Manure supplies nutrients required by plants.
  • Because it originated from plants, FYM naturally
    contains all mineral constituents including trace
  • FYM improves the physical properties of the soil
    by increasing humus content and consequently the
    water holding capacity of the soil.
  • Carbonic acid helps to release minerals present
    in FYM.
  • It releases these nutrients fastest when the soil
    provides warm moist conditions favourable for
    microbial decomposition.

Factors affecting Fertilizer Use
  • Crop factors
  • Certain crops need larger amounts of particular
    nutrients than others e.g. Legumes require large
    amounts of P whereas grains require
    proportionately more N.
  • Crop variety Recently developed varieties are
    more responsive to higher doses of fertilizer
    than traditional crop varieties.
  • Soil Factor
  • Soils differ in their potential for production.
  • Large applications of fertilizer can be
    profitable on soils that have high potential but
    are low in fertility
  • Climatic factor
  • Soils in areas of low rainfall lose little by
    leaching thus nutrients level remains stable. If
    fertilizers are added, the limited amount of
    water available means that the plants are unable
    to respond.
  • Soils of humid regions lose nutrients through
    leaching and weathering but their water supply is
    adequate for high crop production. Here,
    fertilizer application will show good results.

Factors affecting Fertilizer Use
  • Economic factor
  • Fertilizer use is increase by low prices and
    decreased by high prices.
  • Crop prices have the opposite effect High price
    for the crop will give a profitable return from
    large fertilizer application yield but follow a
    curve of diminishing returns
  • Management factor
  • Managers choose the input-output levels at which
    they will operate. Increased crop outputs usually
    require increased fertilizer inputs.
  • Top yields depend on many factors including soil
    type, climate, cropping history, fertilizer
    history and soil amendments, tillage practices,
    weed control and timing of operations. Most of
    these are managerial factors.

Effects of Fertilizer Application on Agriculture
  • Use of mineral fertilizers boosts crop growth
    which harvested provides a considerable amount of
    residue adding the organic content of the soil.
  • When well fertilized, cereals e.g. millet, maize
    and sorghum leave behind considerable organic
    residue in the form of roots, stumps and stalks
  • When nitrogen is applied or a cereal-legume
    rotation is adopted, the organic residue
    undergoes rapid microbial decay to produce humus.
  • Thus the use of fertilizers in conjunction with
    farmyard manure increases the efficiency of crop

Crop Protection
  • Crops are protected against
  • Fire
  • Pests
  • Diseases
  • Weeds
  • Pests and diseases are among the most serious
    limiting factors to economically efficient crop
    production and utilization of natural resources
    in tropical agriculture.
  • Crop losses through pests and diseases may
    sometimes be negligible but at other times total
    loss especially as a result of sporadic outbreaks
    of non-economic pests and diseases.
  • Pests and disease-causing organisms or pathogens
    include rodents, bats, birds, insects, mites,
    molluscs, nematodes, weeds, parasitic plants,
    fungi bacteria, mycoplasma, viruses and sometimes
  • Some diseases are, however, caused by physical or
    soil factors.

Crop Pests
  • Arise in two major ways.
  • Natural occurrence Sudden attack of crops by
    insect e.g. locust outbreaks in arid and
    semiarid regions.
  • Alteration of the ecosystem People attempting to
    change the ecosystems for their own benefit
    creating conditions that favour the development
    of pests. Some of these human activities

Classification of Pests
  • According to damage they cause
  • Biting and chewing insects
  • Piercing and Sucking insects
  • Boring insects

Classification of Pests
  • According to Severity of damage c
  • Key or major pests cause serious and persistent
    economic damage in an ecosystem in the absence of
    effective control measures.
  • Minor pests Cause economic damage only under
    special circumstances in their local environment.

Classification of Pests
  • Numbers of organisms involved
  • Frequency of occurrence
  • Occasional pests
  • Potential pests
  • Migrant pests

Fundamental Principles of Crop Protection
  • Control of pests and plant diseases means the
    reduction in the amount of damage caused.
  • Perfect control is rare, but there is economic
    control when the increase in yield more than
    covers the cost of chemicals, materials and
    labour used for the control operations.
  • The fundamental principles of control include.
  • Exclusion
  • Preventing entrance and establishment of pests in
    farms, states or countries.
  • Involves using certified seeds or plants,
    discarding any that are doubtful, possibly
    treating seeds or tubers before they are planted.
  • For states and countries, exclusion also includes
    quarantine prohibition by law.

Fundamental Principles of Crop Protection
  • Eradication
  • Eliminating pest once already established on a
    plant or in a farm through.
  • Removal of the diseased specimens or cutting off
    cankered tree branches eradication could be aided
    by control viral diseases
  • Cultivation and deep ploughing to bury plant
  • Rotation of susceptible with non-susceptible
    crops in an attempt to starve out the pest
  • Disinfection with chemicals
  • Heat treatment
  • Spraying or dusting foliage with pesticides
  • Treating soil with appropriate chemicals to kill
    insects, nematodes and fungi
  • Trapping rodents

Fundamental Principles of Crop Protection
  • Protection
  • Placing a protective barrier between the
    susceptible part of the host and the pest.
  • In most instances this is a protective spray or
    dust applied to the plant in advance of the
    arrival of the pest.
  • Sometimes it means killing insects or other
    inoculating agents,
  • Storage of food surpluses, preservation by
    freezing, canning, salting etc. can also protect
    the food items from pest damage.

Fundamental Principles of Crop Protection
  • Immunization
  • Control by the development of resistant varieties
    or by inoculating the plant with something which
    will inactivate the pest or pathogen.
  • Avoidance
  • Growing crops during period when the pest
    population is low or absent in the field.
  • Crop is planted to avoid the damaging pest
  • The use of early and rapidly maturing varieties
    can also have profound effect on the degree of
    pest damage experienced by the crop
  • Insects and other arthropods are the most serious
    pests of crop plants in tropical agriculture.

Pest Control
  • Objective
  • To reduce the population of the offending pests
    below the economic threshold when its damage
    becomes uneconomical i.e. does not cause losses
    in yield.
  • A pest control method will therefore be
    considered successful if it can maintain the pest
    population well below the economic threshold.
  • Complete eradication of a pest from an ecosystem
    is not readily practicable or even desirable.
  • Basic principles of pest control include
  • Preventing pests from gaining access to the host/
    Pest-host interaction prevention.
  • Killing the pest directly reduces the population
    of the pest on the host.

Methods of Pest control
  • Include
  • Physical control
  • Legislative control
  • Cultural control
  • Biological control
  • Chemical control
  • Integrated pest management (IPM)

Physical control
  • Includes the use of various barriers to prevent
    pests from physical contact with their hosts and
    mechanical removal or destruction of the pest.
  • Barriers may be mechanical, chemical or
  • Mechanical barriers include
  • Wire fences
  • Mosquito nets
  • Fine nylon net sleeves
  • Nylon or paper bags
  • Sticky bands
  • Boots for waders
  • Concrete foundation - prevent termites.
  • Hand picking
  • Flooding
  • Lethal temperatures
  • Hermetic storage Tightly closed bins
  • Radiation

Physical control
  • Chemical barriers include
  • Prophylactic chemical treatment carried out on
    crops leaving a residual poison that is lethal to
    the pest.
  • Behavioral barriers exploit the fact that pests
    locate their hosts by responding to external
    stimuli such as sight and oduors.
  • They include
  • Frightening devices.
  • Traps
  • Attractants
  • Anti-feedants inhibit feeding of pests

Legislative Control
  • Is the use of laws and regulation to prevent the
    importation of pest organisms into a country and
    to restrict the spread of pests from areas where
    they are already established.
  • Main objective is to prevent dangerous pests from
    colonizing new areas.
  • Include
  • Quarantine Restricts movement of produce from
    areas of infection to other areas
  • Eradication regulations
  • Certification regulation

Cultural Control
  • Is the manipulation of regular agronomic
    practices to influence on the incidence and
    populations of crop pests.
  • The basic principle of cultural control is the
    disruption of the development and life cycles of
    pests either by denying them their food or by
    exposing stages in then life cycle to adverse
    conditions so that they are killed.
  • Advantages
  • Relatively cheap and effective.
  • Poses minimal danger to the environment.
  • Cultural control involves
  • Cultivation of the soil
  • Variation in planting and harvesting dates
  • Crop rotation
  • Close season
  • Trap cropping
  • Resistant crop varieties
  • Mixed cropping
  • Good husbandry practices

Biological Control
  • Is deliberate use of organisms (parasites,
    predators and pathogens) to reduce populations of
  • Such natural enemies may be arthropods (insects
    and mites), bacterial protozoan, fungi, viruses,
    nematodes or even vertebrates (birds, toads,
  • Method is usually used as a supplement to other
    methods of control.
  • Successful biological control requires that
  • Pest population is reduced to levels well below
    the economic threshold.
  • Population is maintained sufficiently low to
    allow the survival of the biological control

Biological Control
  • Biological control requires thorough knowledge of
    the ecosystem, the ecology and behaviour of the
    target pest and the bio-control agent.
  • Advantages
  • It is safe and cost-effective
  • Is devoid of environmental pollution problems
    associated with chemical control.
  • Care must be exercised, however, not to upset the
    ecosystem of the area by the manipulation of
    controlling species.

Chemical control
  • Most common and easily applicable method for
    reducing or preventing economic pest damage is
    the use of toxic substances or pesticides to kill
    or repel pests on their host crops.
  • Continues to play a significant role in solving
    the food and wealth problems of tropical
  • Advantages
  • Relatively easy method of pest control
  • Produces quick and easy results
  • Can be repeated as often as desirable
  • Is cheap and individual farmers can take
    independent action on their own farms
  • The broad-spectrum action of many pesticides
    makes it possible to control a complex of pests
    with one or a combination of pesticides.

Chemical control
  • Disadvantages
  • Is repetitive and must be applied whenever there
    is a pest outbreak. Thus it is wasteful
  • Pesticide applied rarely kills all the pests and
    the residual population which survives soon
    develops to cause economic damage
  • Pesticides can be toxic to beneficial insects
    especially parasites, predators and pollinators.
    They are potentially toxic to wildlife, fish and
  • Cause environmental pollution and ecological
    disturbance. Toxic residues may remain in
    agricultural produce.
  • Pests may develop resistance to a pesticide which
    reduces the effect of that pesticide on that pest
  • Chemical control provides only a temporary
    solution to pest problems
  • Pesticides are expensive to manufacture and
    usually have to be imported by tropical