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Introduction

Lecturer: Ayodele O. P

House Rule

• Attendance is key• Schedule Adherence • All phones on Silence• Decent Dressing • Participatory

DEPARTMENT OF AGRONOMY


Crop protection

Agy 303


Crop protection

Course Outline• Definition of pests.

• The major pests, insect, fungi, bacteria, viruses and nematodes, weeds and other diseases of

tropical crops and stored products.

• Study of insect pests of major local crops, their significance and principles of control.

• Study of the effects of diseases caused by Virus, bacteria, fungi and nematodes. Control of

these diseases.

• Effect of weeds on crops and livestock and the principles and methods of control of weeds.

• Brief outline, shortcomings and advantages of different pest assessment and pest control

methods.

• Strategies of integrated pest control and pest management.

Agy303


• Definitions: Pest

Agy303

Pest can be defined as any organismwhich injuries man, his property or hisenvironment, or which annoys him. Pestis any organism that interferes negativelywith human activities.

A pest can be described as any organism capable of causing damage to crop plants.

According to Edward & Heath (1964), the pest status is reached when there is 5% loss in yield of a particular crop.

The pest concept is anthropocentric and circumstantial. It is anthropocentric the sense that man is the central focus and circumstantial in the sense that an organism may be a pest under one condition and be beneficial in another situation.

DEPARTMENT OF AGRONOMYAgy303

Insects Fungi

Weeds

Nematodes

Examples of Pest

Birds

Rodents Bacteria

Concepts for Appraising Pest Situation

Economic Damage

Economy Injury Level

Economic Threshold

DEPARTMENT OF AGRONOMY Agy303

Definitions of Pest Concepts

Economic Damage

This is the lowest pest population density that can cause economic damage. EILis the number of pest that will cause a damage that is equal to the cost ofcontrolling the pest

Economic Threshold

Economic Injury Level (EIL)

This amount of damage done to the crop that will justify the cost of artificialcontrol measure. It is damage done to crop by pest that is statistically significantat 5% level of probability.

The pest population density at which control measure should be started orintroduced to prevent the ever increasing pest population from reachingEconomic Injury Level.

DEPARTMENT OF AGRONOMY Agy 303

Economic Threshold

Where,

ET = Economic ThresholdC = Cost of implementing control measureP = Price of crop per toneD = Loss in yield (t ha-1) associated with the number of pestK = Reduction in pest by use of control measure

C .

PDKET =


The idea of economic threshold is based on the fact that organism inrelatively stable environment will reach a state of equilibrium in theenvironment over a time

There is an average population density which is stable over a long period oftime. The Economic Threshold and Economic Injury Level are normallyabove the average population.

Economic Threshold


THORITICAL PEST POPULATION IN REACTION TO ECONOMIC THRESHOLD & ECONOMIC INJURY LEVEL

The Non-economic / Potential Pests:

These are pests whose population level never reaches the Economic Threshold or Economic Injury Level

Occasional Pests:These are pests whose populationoccasionally reaches EconomicThreshold or Economic InjuryLevel. The variegatus grasshopper(Zonocerus variegatus) in WestAfrica and host of Lepidopterouslarva (butterfly) attacking deciduousforest trees, arable as well asplantain crops are examples.

Population



Key or Major Pests: They are pests whose population frequently reaches the Economic Threshold or Economic Injury Level. They perennially inflict damage on crops and their population level hardly fall below Economic Threshold level. Examples is the case of Maruca testulalis on cowpea, Dysdesus spp and red boll worms on cotton.



Perennial Pests:

These are pests whose population is always above the Economic Injury Leveland Economic Threshold. Control measures should be introduced immediatelysuch pest is seen.


Conditions that Promote Pests

Favourable climatic conditions

Change in the character of the food supply

Change in cultural practices

Biological change

Introduction to new environments

Change in host/natural enemy relationships

Loss of competing species

Economic change


INSECT PEST

• Entomology is a branch of biology that focuses on the study of insects

Kingdom

Animalia

Phylum

Arthropoda

Class

Insecta

Insects could be further classified based on Family, Order, Genus and Species

Apterygota (wingless)

Pterygota (winged)

The class “INSECTA” could be divided into winged and wingless insects calledPterygota and Apterygota respectively.

The class “INSECTA” possesses 28 Orders. Each order is divided into families.

DEPARTMENT OF AGRONOMYAgy 303

INSECT PEST

• The housefly could be classified as thus

Kingdom

Animalia

Phylum

Arthropoda

Class

Insecta

Family

Muscidae

Order

Diptera

Genus

Musca

Species

domestica

Common and Scientific names of some insects are:

Larger Grain Borer – Prostephanus truncatus

Lesser Grain Borer – Rhizopertha dominica

Bean Weevil – Callosobruchus maculatus

Maize Stalk Borer – Busseola fusca

Elegant Grass Hopper – Zonocerus variegatus

Honey Bee – Apis mellifera

DEPARTMENT OF AGRONOMYAgy 303

INSECT PEST

• Characteristics of Insect Pest

Possession of one pair of antennae

Possession of one pair of eyes

Possession of three pairs of legs

Possession of breathing tube or trachea

Possession of one or two pairs of wings

Possession of maxillae and mandible

Body divided into head, thorax and abdomen

Post-embryonic development is usually by metamorphosis

Abdomen is devoid of ambulatory appendages

Possession of chitinous exoskeleton

Possession of segmented that bears paired limbs


Grasshopper Body Parts

Insect Morphology: External Anatomy


Insect Morphology: External Anatomy

THE HEAD: The head bears the antennae, the mouth part and the eyes. The

compound eyes are located on either side of the head and composed of hexagonal

facets called corneal lenses. Compound eyes are complex and diverse.

ANTENNAEThese are paired appendage that articulate with head

capsule and are located on the anterior part near the

compound eye.

The mouth part of a chewing insect such as the grasshopper has upper lip called the labrum;

and a lower lip called the labium. These two serve to hold the food

MOUTH PARTSThis varies with feeding habits.

The upper jaws or mandibles are for crushing; and the lower pair, the maxillae manipulate

(breaks it into smaller particles) the food


LEGS:

The generalized insect legs consist of six

segments as follows:

(i) a basal coax

(ii) Trochanter

(iii) Fermur

(iv) Tibia

(v) Tarsus

(vi) Pretarsus

THE THORAX: The head is attached to the thorax by means of a membranous region,

the neck or cervix. The insect thorax is divided into three segments namely; Prothorax,

Mesothorax and Metathorax. On the each of the segment is a pair of legs in winged

insects. The thorax also bears one or two pairs of wings. Spiracles which are the external

openings of the respiratory system are located on each side of the pleura


Leg types

Cursorial walking and running

Fussorial

Salfatorial

Raptorial

forelegs highly modified bearing heavily sclerotised

digging claws

with forelegs modified for grabbing and holding preys

with enlarged hind legs that accommodate muscles used in

jumping

Natational with leg modified for swimming

DEPARTMENT OF AGRONOMYAgy303

WING: The wings are borne on either or both the mesothorax and metathorax segments.The wings arise as outgrowth of the integuments between the tergal and pleuralsclerites. There are considerable variations in the wings of insects with respect tosize and veination.

Functions: The most obvious function of the wings is for flying; however, wingshave been modified for; (i) Protection: - e.g. hard forewings of the beetles. (ii)Production of sound e.g. the Homoptera (iii) Stability of flight: - Trueflies withbalancers

ABDOMEN: The abdomen typically has 11 segments; though no more than 10 are visible. It contains a large part of the digestive system. The terminal segment may bear a pair of appendage called CERCI.


Economic Classification of Insects

Insects are a very important group of animals because of their beneficial

and adverse effects on the life of man.

Household and Disease Carrying Insect

Injurious Insects

Beneficial Insects

Helpful Insects


Economic Importance of Insect Pests

This refers to the merits and demerits of insect pests.

Reduces values or quality of foodReduce yield or quantity of output. Vector of Diseases Injuries to Man and Animals Effects of Recreation. Effects on Stored Products, Household and Structural Materials

Demerits

Agent of Pollination Subject of Scientific or Biological Studies Source of Drugs Predators and Parasites.Aeration of Soil Food for Man and Animals.

Merits


General Classification of Insects

Subclass Apterygota- primitively wingless insects

1 Protura - Proturans2 Collembola - Springtails 3 Diplura - Diplurans 4 Thysanura - Bristletails 5 Microcoryphia - Jumping bristletails



Subclass Pterygota: Winged and secondarily wingless insects.

6. Ephemeroptera - Mayflies 7. Odonata - Dragonflies and damselflies 8. Orthoptera - Grasshoppers, crickets, cockroaches, mantis

and walkingsticks9. Dermaptera - Earwigs 10. Isoptera - Termites 11. Embioptera - Web spinners 12. Plecoptera - Stoneflies 13. Zoraptera - Zorapterans14. Psocoptera - Psocids15. Mallophaga - Chewing lice 16. Anoplura - Sucking lice 17. Thysanoptera - Thrips18. Hemiptera - Bugs 19. Homoptera - Aphids, scale insects, hoppers, cicadas,

psyllids and whiteflies.



Division Endopterygota - Complex body change during growth

20. Neuroptera - Alderflies, anthions, dobsonflies, fishflies, lacewings, snakeflies and owlflies

21. Coleoptera - Beetles 22. Strepsitera - Twisted-winged parasites 23. Mecoptera - Scorpionflies24. Trichoptera - Caddisflies 25. Lepidoptera - Butterflies and moths 26. Diptera - Flies and mosquitoes 27. Siphonaptera - Fleas 28. Hymenoptera - Ants, bees, wasps and sawflies



Isoptera - Termites

Coleoptera - Beetles

Diptera - Flies and mosquitoes

Hymenoptera - Ants, bees, wasps and sawflies

Focus


Order Isoptera - The Termites

• Example is Macrotermes nigeriense (Edible termites).

• Insects in this order are termites, soft bodied insects that live together in

large communities. Primitive species tunnel into wood, others build large

ant hills (termitaria) made up of faeces, saliva and mud.

• Termites have biting mouth parts.

• The two pairs of elongated wings are very similar, hence the name Isoptera

meaning equal wings.

• Some lower termites feed on wood, digested through the help of symbiotic

protozoa e.g. Trichonympha in the gut while the higher termites feed on

fungi, humus and soil organisms and maintain a garden of fungi to feed

the young ones and the queen.



They are polymorphic i.e. exist in different forms or castes. They appear in

three basic forms:

• Reproductive forms

The winged-reproductive forms usually swarm after heavy rains especially

in the mornings and night, they cast off their wings after flying for some

time

• The soldiers (sterile males and females)

The soldiers have highly sclerotised head with well-developed mandibles.

• The workers (Sterile males and females).

The workers enclose the queen and king in a royal chamber. There are

numerous workers in the colony, who are responsible for building nests,

fetching food, nursing the young and cleaning the nest with their mouth

parts.


Order Coleoptera (The Beetles)

• This order is the largest order in the animal kingdom.

• Coleopterans are essentially terrestrial insects, found in soil or decaying

matters on soil. Some are aquatic e.g. Dytiscus (water beetle).

• Most beetles in this order are of economic importance because they destroy

farm crops, timber and stored products.

• Fore wings are modified into hard protective elytra which meet in a line

down the back.

• Hind wings are membranous and folded beneath the elytra (forewings) and

sometimes the hind wings may be absent.

• Mouth parts are biting type.



• Beetles undergo complete metamorphosis from egg - larva - pupa. Hence

three types of larva appear in different members of this order.

Compodeiform: Active predatory larva with

well-developed antenna, legs, and sensory

organs.

Eruciform (Scarabeiform): These are “C

Shaped with large sclerotised head. Thoracic

legs are well developed and abdomen is

inflated, soft and whitish in colour.

Apodous: (Legs absent): Are crescent shaped and eyeless found in groups living

in groups in food e.g. weevils.


Order Diptera (The True-Flies)

• They are commonly known as true flies, members of this order include

mosquitoes, houseflies, midges, and sandflies.

• A representative feature of this order is presence of a single pair of

membranous wings which are borne on the enlarged mesothorax.

• The hind wings are modified to a pair of halters or balancers.

• Mouth parts for sucking alone or for piercing and sucking.

• Many feeds on nectar of flowers or decaying organic matters, examples

include mosquitoes, midges; tsetse flies that notably sucks blood.

• Members in this order undergo complete metamorphosis


Order Diptera (The True-Flies)

Economic importance of flies

• Either as adults or as larvae, the bloodsucking flies transmit pathogenicorganisms causing various diseases,such as malaria, sleeping sicknesselephantiasis, yellow fever andfilariasis.

• Housefly act as mechanical carriers ofgerms on their legs, hairy body andcontaminate food. Their larva causeinjuries to crops and their activitiesresult in great financial losses

Mosquito

House fly


Order Hymenoptera

• This order constitutes sawflies, bees, ants, wasps.

Members are large and about 100,000 species.

• They exhibit interesting social habit, instinctive

behaviour, polymorphism, parasitism and

communication.

• Wings are membranous and have biting mouth type

modified for licking and sucking.

• The larva may be polypodous (with many legs) or

Apodous (without legs) like a caterpillar


• Honey bees yield honey and wax

• Bees are important pollinators of flower

• Parasitic hymenoptera are helpful in the biological

control of injurious insects

• Family Vespoidea – wasps are carnivorous, they

paralyse caterpillars with their sting and store them

in the nests for young ones to feed on.

• Family Apoidea – bees hind legs are highly

modified for pollen collection stored in their nest

for their larva, while workers function as nurses,

ventilators, cleaners foragers depending on their

age.

Economic importance of Hymenoptera


What is Phytopathology?

Greek = Pathos (suffering)Phyton (plant) Logos (study)

It is the study of the suffering plant

Plant pathology is that branch of agricultural, botanical or biological scienceswhich deals with the study of:

Cause of the disease

Resulting losses and

Control of plant diseases

Concepts of Plant Disease


Objectives of Plant Pathology

• Study of origin, causes or reasons. Study of living, non-living and other

causes of disease or disorder in plants- Etiology:

• Study of mechanism of disease development i.e. processes of infection and

colonization of the host by the pathogen. This phase involves complex host-

pathogen interactions- Pathogenesis

• Study the interaction between the causal agent and the diseased plants in

relation to environmental conditions. Generally at the population level-

Epidemiology

• Development of management systems of the diseases land reduction of

losses caused by them- Control / Management.


What is health?

The ability to carry out normal physiological functions at a acceptable level consistent to genetic potential.

Normal physiological functions include:

– Normal cell division, differentiation and development;

– Absorption of water and minerals from the soil and translocation;

– Photosynthesis and translocation of photosynthates;

– Utilization and storage of photosynthates;

– Metabolism of metabolites and synthates;

– Reproduction;

– Storage of reserves for overwintering or reproduction

Plant pathology is both science of learning and understanding the nature of

disease and art of diagnosing and controlling the disease


• Marshall Ward (1901): Disease represents a condition in which functions ofthe plant are not properly discharged.

• Disease is a harmful deviation from normal functioning of physiologicalprocesses. (British Mycological Society, 1950)

• Horsfall & Diamond (1957): Disease can be defined as a physiologicaldisorder or structural abnormality that is deleterious or harmful to theplant or its part or product that reduces its economic value.

The process in which a pathogen interferes with one or more essential plantcell functions

Disease

• Disease can be defined as the result of interaction between host, pathogenand environment


• By utilizing host cell contents

• By killing host or by interfering with its metabolic processes

through their enzymes, toxins etc.

• By weakening the host due to continuous loss of the nutrients.

• By interfering with the translocation of the food, minerals land water.

• They can suppress the chlorophyll content.

• They can reduce the leaf area.

• They can curb the movement of solutes and water through the stems.

• They sometimes reduce the water-absorbing capacity of the roots.

• They suppress the translocation of photosynthates away from the leaves.

• They sometimes promote wasteful use of the products of photosynthesis as

in the formation of galls.

There are many ways in which plant disease pathogens can affect plants

Disease


Disease Triangle

Environment

Disease

Pathogen Host

TIME

Conditions for disease

• Host should be susceptible

• Pathogen should be virulent

• Environment should be favourable for the disease


• Blights • Rusts • Smuts • Rots • Wilt

Based on type of symptoms Based on type of crop

• Cereal diseases

• Vegetable diseases

Based on type of organ affected

• Fruit diseases • Root diseases

Based on cause

• Infectious diseases

• Non-infectious disease


• Fungi• Bacteria• Virus• Nematodes

Living Organisms Non-living Organisms

• Unbalanced soil fertility

• Toxic chemical

• Air pollution

• Frost

• Drought

• Sunburn

• Wind

Plant Disease Agents


• Fungi• Bacteria• Virus• Nematodes• Viroids• Virusoids• Protozoa• Algae• Parasitic Plants

• Environmental stress / excess

Temperature e.g. high or low Moisture e.g. excess- rotting or Stress wilt /drying Air Light e.g. etiolation

• Nutrition Imbalanced

Excess Deficiency e.g. N deficiency, Zn deficiency

Infectious Plant Diseases Causes

Non-infectious diseases

An abnormal physiological change due to non-parasitic agent or non-parasiticphysiological malfunctioning due to either excess or deficiency in environmentalfactors or nutrients

Disorder


Terminology

• Parasite

• Pathogen

• Pathogenicity

• Pathogenesis

• Symptom

• Sign

• Syndrome

• Hypersensitivity

• Host

• Alternate host

• Collateral host

• Resistance

• Susceptibility

• Tolerance


Terminology

• Parasite : An organism that lives on or in another organism and obtains foodfrom the second organism.

• Pathogenicity is the ability of a pathogen to cause the disease by interferingwith one or more of the essential plant cell function.

• Pathogen: Any entity that can cause disease in a host e.g. fungus, bacteria, virus, phytoplasma, viroids, RLO’s, parasitic plants, nematodes.

• Symptom – are the expression of the disease caused by the manifestation ofthe physiological reaction of the plant due to harmful activity of the pathogen

• Sign - physical evidence of the presence of disease agent (e.g., mold or fungalspores, bacterial ooze)


Terminology

• Syndrome : Defined as sequential appearance of disease symptoms on a plantduring the development of the disease or sum total of symptoms exhibitedby a disease For instance, necrotic spot - blight -fungal growth -death oforgan or plant

• Biotroph: A plant-pathogenic fungi which establishes a long- termrelationship with the living cells of host without killing it as part of theinfection process.. e.g. Rusts, powdery mildew

• Necrotrophs: – kill their host before feeding on the cells or the cell’s contents and live on dead tissue. e.g Rhizoctonia

• Host: Any organism that harbours another organism is called host .

• Alternate host: is the host that help in the completion of the life cycle of thepathogen and its survival, belong to different family.


Terminology

• Collateral host: host of the same family and help in the survival of thepathogen

• Infection: Establishment of organic relationship between host and pathogen

• Pathogenesis: Chain of events that takes place during the development ofdisease (inoculation to survival of the pathogen)

• Susceptibility: Inability of the host to resist the attack of the pathogen

• Resistance: Ability of the host to resist the attack of the pathogen – Horizontalresistance – Vertical resistance

• Hypersensitivity: is the quick death of the host tissue in the vicinity of thepathogen


Terminology

• Disease escape: it is ability of the susceptible host to avoid the damagingdisease stress e.g. unfavourable environment / growth habit

• Virulence: It is defined as the degree of pathogenicity of a particular isolate orrace of the pathogen.

• Aggressiveness: it is the capacity of the pathogen to invade and colonize thehost and to reproduce on or in it.

• Predisposition: it is the set of conditions that makes the plant vulnerable tothe attack of the pathogen.

Thank you

Lecture slide Created by Ayodele O. P

[email protected]

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