Crop Protection Review

EDITO B. SUMILE, Ph. D.

Plant Pathology Deals with the study of nature, causes and control of plant

disease

Art of dealing with the application of knowledge gained from studying science which include disease diagnosis, assessment, forecasting, recommendation and appropriate control and field application of suitable control

The ultimate objective of Plant Pathology is to prevent or minimize plant diseases not only to increase food production but also to maintain quality and quantity of harvested commodity until it reaches to the consumers.

Economic Importance of Plant diseases Men and other forms of animals exist solely on

earth as guests of the Plant kingdom because only the green plants can produce their own food

Plants are the only source of food, clothing, shelter and numerous luxuries, drug, etc.

When disease kills plant, all forms of life will be adversely affected

Types of Crop Losses Reduction in yield

Deterioration of harvested produce during storage, marketing or transport

Reduction in quality of the produce

Production of toxins

Predispose the plants to other infection

Diseases increase production cost

Development of Plant Pathology in the Philippines Coffee rust and coconut bud rot were the first disease being studied in the

country

Coffee rust was first noted in Batangas in 1885 and in 1890, coffee plantations in that area were totally devastated

Coconut bud rot was reported by Dr. Copeland the first dean of Agriculture in UPLB established in 1908.

B. Robinson (1911) reported occurrence of leafblight in corn

Baker (1912) reported downy mildew of corn and published his book “The lower Fungi in the Philippines Islands” in 1914

Reinking (1918) published the “ Philippine Economic Plant Diseases”

Unit 2Concepts of Plant Disease Whetzel (1912)- defined disease as malfunctioning caused by animate agents; physiogenic disease

caused by inanimate agents

Stakman and Harar (1957)- any deviation from normal growth or structure of plants that is sufficiently pronounced and permanent to produce visible symptoms or to impair quality or economic value

Horsefall and Dimond (1959)- malfunctioning process caused by a continued irritation

National Academy of Science (1968)- harmful alteration of the normal physiological and biochemical development of plants.

Merril- dynamic interaction between an organism and its environment which result in abnormal physiological and morphological or neurological changes in the organism

Agrios (1978)- any disturbance brought about by a pathogen or an environmental factor which interferes with manufacture, translocation or utilization of food, mineral nutrients and water in such a way that the affected plant changes in appearance or a decrease in yield

Definition and Terminologies in Plant Pathology Pathogen- any agent that causes the disease

Parasite – an organism which depends wholly or partly on another organism

Obligate parasite- organism that is restricted to subsist on living organism and attacks only living tissues.

Facultative parasite- organism which subsist on no-living materials (saprophytes)

Host- refers to the plant that is being attacked by a parasite

Pathogenesis- refers to the chain of events leading to disease development in plant

Pathogenicity- the capacity of a pathogen to cause disease.

Symptoms- expression of the plant of a pathologic condition

Signs- expression of the pathogen causing the disease.

continuation Primary symptoms- immediate and direct results of the causal agent’s activities on

the invaded tissues

Localized symptoms- distinct and limited expression

Histological symptoms- expression that are observed only under a microscope examination

Hypoplastic symptoms- inhibition or failure in the development of some aspect of plant growth as in stunting

Hyperplastic symptoms- overdevelopment of plant tissues as in gall formation

Plant disease diagnosis- is the identification of specific plant disease through their characteristics symptoms and signs including factors related to disease development

Classification of Plant Diseases

Classification according to the affected plant organ- root diseases, leaf disease, fruit diseases, etc

According to symptoms – leaf spot, rust, smuts, etc.

According to type of affected plants – vegetable disease, field crop diseases

According to type of pathogen- infectious, non-infectious

Unit 3Non-parasitic agent of Plant Diseases Common non-parasitic agent:

Excessive low temperature Too high temperature Lack of oxygen Too much /little oxygen Adverse meteorological conditions Air pollutants Mineral deficiencies Mineral excesses Unfavorable soil pH Excessive pesticide levels Improper agricultural practices Lack/excess soil moisture Naturally occurring toxic chemical

Disease caused by too low temperature Freezing injuries Chilling injuries

Diseases caused by too high temperature Sunscald Heat necrosis

Disease caused by lack of oxygen Black heart of potato

Too much/ too little sunlight Etiolation Scorching

Adverse meteorological condition Strong winds Heavy rains lightning

Air pollution Ethylene Nitrogen oxides Peroxyacetyl nitrates Ozone Particulates

Parasitic agents of Plant Disease Viruses and Virus-like pathogens

Very small particles With several shapes; spherical, rigid rod Consist of nucleic acid surrounded by protein coat

Symptoms of virus infection Reduction in growth Reduction in vitality Color deviation Water shortage Tissue and plant death Malformation Anatomical abnormalities

Virus Transmission

Transmission by vegetative propagation Transmission through sap Seed transmission Insect transmission Mite transmission Nematode transmission Fungal transmission Dodder transmission

Symptoms of virus infections Reduction in growth- stunting or dwarfing Reduction in vitality-increase susceptibility to

other pathogens Color deviation

Mosaic- shades of green and yellow are usually irregular angular but sharply delimited

Flecking or spotting- if discolored part is sharply bordered but circular

Mottling- diffusely delineated variegation Chlorosis-less chlorophyll is produce (yellowing)

Symptoms of virus infection

Water shortage Wilting-due to excessive transpiration or impeded supply Withering-irreversible desiccation of tissues and implies death

Tissue and plant death Malformation-imbalanced development (leaf rolling, curling,

distortion) Rugosity-retarded growth of veinal tissue Rosetting-shortening of internodes Epinasty-curling or turning of leaves downward Enation-outgrowth of leaves, veins, stems Swellings/tumors-enlargement of stem or roots

Symptoms of virus infection Anatomical abnormalities

Hypotrophy-decrease in cell size Hypoplasia-decrease in cell number Hypertrophy-increase in cell size Hyperplasia-increase in cell number

Control of Plant Viruses Exclusion-systems of quarantine, inspection and

certification Eradication of infected plants or plant parts Controlling of insect vectors and removal weeds

serving as host Soil fumigation for soil infested with nematode Use of virus-free planting materials Use of resistant varieties Tissue culture

Bacteria as Plant Pathogen Unicellular organism reproduce asexually by binary fission Absence of chlorophyll Genera of Pathogenic Bacteria

Acetobacter Curtobacterium Rhizobacter Acidovorax Enterobacter Sphingomonas Arthrobacter Erwinia Rhodococcus Bacillus Gluconobacter Serratia Breneria Nocadia Spiroplasma Burkholderia Pantoea Streptomyces Clavibacter Pectobacterium Xanthomonas Clostridium Pseudomonas Xylella Corynebacterium Ralstonia Xylophilus

Common examples of plant disease caused by bacteria Pectobacterium carotovorum - soft rot of

vegetables Ralstonia solanacearum - bacterial wilt of

solanaceous crops Xanthomonas citri - citrus canker Xanthomonas oryzea - bacterial leaf streak of rice Agrobacterium tumefaciens - crown gall of plants Pectobacterium chrysanthemi - stalk rot of corn Streptomyces scabies - potato scab

Symptoms of disease cause by bacteria

Leafspot Soft rot blight, Gall Canker wilting

Mycoplasma as Plant pathogen Non-motile, non-spore-forming, polymorphic

microorganism that lack cell walls and are bounded by triple-layered unit membrane

Sensitive to tetracycline but resistant to penicillin

Reproduce through transverse binary fission Three families: Mycoplasmatacea,

acholeplasmatacea, spiroplasmatacea Common vectors: leafhoppers, planthoppers,

treehoppers, aphid, mite and psyllids

Symptoms and diseases caused by Mycoplasma Aster yellow-general chlorosis and stunting

of plants Spiroplasma citri- stubborn disease of

citrus; plants affected exhibit an upright bunchy growth of twigs and branches with shortened internodes and numerous shoots. Fruits and leaves are small and deformed; diseased fruits have bitter taste and disagreeable flavor and smell.

Fungi as Plant Pathogen Spore-forming organism Chorophyllous with filamentous vegetative

structures known as mycelium The True Fungi

Phylum Chytridiomycota Phylum Zygomycota Phylum Ascomycota Phylum Basidiomycota

Diseases caused by fungi Pythium debaryanum – cause damping off Phytophtora infectans – causes leaf bight of potato Phytophthora palmivora – coconut bud rot Albugo candida – white rust of crucifers Plasmopara viticola – downy mildew of grapes Peronosclerospora philippinensis – downy mildew of corn Bremia lactucae – downy mildew of lettuce Pseudoperonospora cubensis – downy mildew of cucurbits Olpidium brassicae – parasitic in roots of cabbage Physoderma maydis – brown spot of corn Synchytrium psopocarpii – orange galls of winged beans Rhizopus nigricans – soft rot of fruits and vegetables Choanephora cucurbitarum – soft rot of squash Eryphe graminis – powdery mildew of grasses

Nematodes as Plant Pathogen Thread-like organism, non-segmented, bilaterally symmetrical and are usually

elongated and cylindrical in shape Groups of parasitic nematode

Semi –endoparasites Rotylenchus reniformis – reniform nematodes Tylenchulus semipenetrans – citrus nematodes

Endoparasite Pratylenchus – lession nematode feeding on the root cortex Radopholus similis – burrowing nematode of banana Hoplolaimus – lance nematode Helicotylenchus – spiral nematode Meloidogyne – the root-knot nematode Heterodera/Globodera – the cyst nematode

Ectoparasite Belonolaimus – string nematode Paratylenchus – pin nematode Trichodorus – stubby root nematode of field crops and vegetables Xiphinema – dagger nematode of trees and many annuals

Inoculum, Inoculum Survival and Inoculation Inoculum – any part of the pathogen that

could initiate infection Infection court – any part of the plant where

the inoculum could initiate infection Types of inoculum

Fungi – spore , mycelia, sclerotial bodies Bacteria – bacterial cells, ooze Nematode – eggs, larvae, adult

Different Sources of Inoculum Infected living plants Plant debris Infected soil Infected seed/vegetative propagating

materials Contaminated containers, storage areas,

equipment Insects, nematode and other living agents

Dissemination Transfer of inoculum to an infection court Steps in dissemination

Take-off – getting the inoculum into the air Flight – moving the inoculum from one place to the other Deposition – settling of the inoculum from the atmosphere

Types of dissemination Wind dissemination Rain dissemination Insect dissemination Seed and planting materials Man dissemination

Disease Cycle Is the sequence of events that leads to and is involved in

disease production Parts of the disease cycle

Inoculation-deposition of inoculum Penetration-entry of pathogen inside the host

Passive-pathogen plays no active role Active- pathogen directly participate in the penetration

Infection-when pathogen established and obtain food from the host Colonization-growth of the pathogen to the host tissues Incubation-from inoculation to the production of visible symptoms Dissemination-spread or transfer of the inoculum Survival-the tiding over of the pathogen on adverse condition

Plant defense mechanism Defense mechanism to penetration

The cuticle offers physical and chemical barriers Closed or partially closed stomates Chemical barriers

Cutin of citrus contains acid toxic to organism Colored onion contains catechol and

protocatechuic acid

Passive defense mechanism Unavailability of nutrients in the host and

inadequate enzyme potential of the pathogen Pre-formed toxic substances inside the cell

Tannins and phenolic cpds-caffeic acid, chlorogenic acids and hydroquinones have fungitoxic properties

Osmotic pressure and parasitism-plants with high osmotic pressure and reduced permeability would make it difficult for invading organism to obtain water and nutrients from them, thus rendering them more resistant

Active defense mechanism Mechanical barriers to pathogenenis Hypersensitivity and phytoalexins

Hypersensitibity-the rapid localized death of host cells around the pathogen

Phyto-alexins-subtances formed by the host not only in response to pathogenic invasions but also to injury and foreign inanimate and animate agents

Post-insfectional toxic substances detoxification

Other terminologies Epidemiology – study of disease development in population Epidemic – widespread, explosive disease outbreaks Epiphytotics – refers to the epidemics of plant disease Endemic disease - native or indigenous to a particular place Exotic disease – introduced from some other areas Pandemic disease- worldwide or widespread occurrence

throughout the continent or region Sporadic disease – occur at irregular intervals Disease forecasting – predicting when a disease will occur and how

severe it will be for farmers to be guided properly in making decisions on disease control

Disease assessment – appraisal on the amount of disease present and relate these to yield loss

Factors affecting the development of epidemics

Susceptible plants Practice of monocropping Predisposition of plant to infection due to

excessive use of N fertilizer Presence of abundant inoculum and

efficient vectors

Principles of Plant Disease Control Exclusion – prevention of new pathogen from

being introduce into a locality Protection – involves the prevention of infection

by putting a barrier between the pathogen and the host

Eradication – measure that eliminate, inhibit or kill the pathogens that have become established within the plant or area

Immunization – modifying certain physiological features or physical features of the host so that it can repel infection

Terms related to Immunization Resistance – the relative ability of the plant to overcome the effects of the

pathogen

Tolerance- the ability of the suscept to undergo severe infection without serious reduction in yield.

Klenduscity – the lack of infection in a susceptible plant due the suscept’s effect on something other than the pathogen

Escape – the suscept is not infected due to certain circumstances as unfavorable environmental condition or luck of inoculum

Virulence – a measure of the degree of infection or pathogenicity

Aggressiveness- a measure of the rate at which virulence is expressed

Types of resistance Vertical resistance-controlled by one or few

genes and is effective only against one or few races of the pathogen

Horizontal resistance-controlled by several genes and is theoretically effective against all races/strains of pathogen.

Methods of plant Disease Control Sanitation Cultural methods-crop rotation, concept on sustainable agriculture,

fallowing, tissue culture Physical methods-heat treatment, low temperature storage,

irradiation Chemical method-seed treatment, fumigation of soil/warehouse,

control of insect vectors Biological method-use of microorganism that compete with,

parasitize or are antagonistic to the pathogen Cross protection-protection by a mild pathogen virus strain against infection

by another strain of the same virus which is more virulent Interference-mycorrhizae interfere with pathogen Use of bacteriophages Use of parasites Use of resistant varities

Entomology Study of insect, their nature, effects and control Insect Classification

Super class Hexapoda – six legged organism Class Parainsecta –designates small, wingless, soil-dwelling

arthropods of the order Protura and Collembola Class entognatha- small wingless, soil dwelling arthropods

that have their mouthparts retracted in the head. Class insecta- insects do not have their mouthparts

retracted in the head

Basic Concept of Entomology Insects –derived from the latin “insecare” meaning “to cut into”

refering to the bodies of some insects that are almost cut in half by constriction of the neck and waist

Subclass Apterygota-insects without wings Subclass Pterygota – insects with wings Infraclass Paleoptera-winged insects that unable to fold their wings

flat over their bodies Infraclass Neotera-meaning “modern type of wings” insects that

can fold their wings flat over their backs Division Exopterygota-wings developed externally and are visible

on the youngs as small wing pods Division Endopterygota-have wings rudimentary that develop

internally during the early life of the insects. Life history is divided into two groups that are strikingly different forms and habits

Characteristics of Insects More or less elongate and cylindrical in form Bilaterally symmetrical Segmented body regions Paired segmented appendages Chitinous exoskeleton Tubular alimentary canal with mouth and anus Open circulatory system

Insect Body Parts

Insect body regions Head

One pair of antenna Compound eyes and ocelli One pair of mandible One pair of maxilla A hypopharynx A labium

Front Head

The mouthparts Labrum-upper lip Hypopharynx-tongue Pair of mandible-jaws Pair of maxillaserve as accesory jaws

aiding in the holding and chewing of food Labium-lower lip

Insect mandible

Insect Labium

Insect Maxilla

Types of mouthparts Mandibulate/chewing mouthparts

Adapted for chewing

Haustellate/sucking mouthparts Adapted for sucking

Position of mouthparts Hypognathous-the mouthparts hang

ventrally from the head capsule Prognathous-anteriorly directed position of

the mouthparts Opisthognathous-mouthparts are directed

ventroposteriorly relative to the head capsule

The thorax Three pairs of legs Often one or two pairs of wings, borne by

the second and/or third of the three thoracic segments

The abdomen The gonophore at the posterior end of the

abdomen No locomotor appendages on the abdomen

of the adult

The body wall Covered by exoskeleton It serve not only as covering of the body but

as a supporting structure, muscle attachment and reception of external stimuli

The insect antenna Are paired segmented appendages located

on the head usually between or below the compound eyes

It acts as organ of taste, organ of smell and in some cases organ of hearing

Parts of the insect antenna Scape-the basal segment Pedicel-second segment Flgellum-remainder

Forms of antenna Setaceous-bristlelike, the segment becoming more slender distantly. Ex.

Dragonfly, damselfly and hoppers Filiform-threadlike, the segments nearly uniform in size, and usually

cylindrical. Ex. Ground beetle, tiger beetle Moniliform-like string beads, the segments are similar in size and more or

less spherical in shape Serrate-sawlike, the segment, particularly those in the distal half or two

thirds of the antenna more or less triangular. Ex. Click beetle Pectinate-comblike, most segment with long slender, lateral processes Clubbed-the segments increasing in diameter distantly

Clavate-increase is gradual Capitate-if the terminal segments are rather suddenly enlarge Lamellate- if the terminal segments are expanded laterally to form rounded or oval

platelike lobes Flabellate-where the terminal segments have long, parallel-sided sheetlike, or

tongue-like lobes extending laterally

Continuation…… Geniculate-elbowed, with the first segment long

and the following segments are small Plumose-feathery, most segments with whort of

long hairs. Ex. Male mosquitoes Aristate-the last segment usually enlarged and

bearing a conspicous dorsal bristle, the artista; Ex. Housefly

Stylate-the last segment bearing an elongate terminal styletlike or fingerlike process the style. Ex. Robber fly

Some Insect Antennae

The thorax The middle region of the body and bears the legs

and the wings (functionally, it is the locomotory tagma)

Composed of the three segments, the prothorax, mesothorax and the metathorax

Each segments bear a pair of legs Meso and the metathorax bear the pairs of wings.

If there is only one pair of wings they usually borne from the mesothorax

The legs Six segments

Coxa-basal segment Trochanter-small segment following the coxa Femur-first long segment of the leg Tibia-second long segment of the leg Tarsus – segmented Pretarsus-may consist of a single claw

Modification of the legs Apodous-lacking legs Ambulatory-adapted for walking Cursorial-adapted for running Fossorial-adapted for digging Raptorial-adapted for grabbing and holding prey Saltatorial-adapted for jumping Natatorial-adapted for swimming

Specialized structures Corbiculum-legs of honey bees as pollen

basket Tympana- auditory organ Pulvilli-found in the lower surface of each

tarsal segments as in the several members of the orthoptera

The wing Modified to:

Membranous-wings that are transparent Tegmina-thickened, leathery wing of

grasshopper Elytra-hardened forewings of beetles Hemilytra-base of the forewing harden while the

remaining are membranous Halteres-a pair of highly modified, club-shaped

structure important in the stability of flight

Wing-coupling mechanism Hamuli - tiny hook found among

hymenopterans Frenulum - spinelike found in moths Jugum - lobelike found in lepidopterans

The abdomen 11 segments Terminal segment bears a pair of appendages,

the cerci Spiracles, the external ventilatory organ in each

segments Female gonophore usually in the 8th or 9th

segment Male copulatory organ-aedeagus found in the 9th

segment

Types of metamorphosis Metamorphosis-is a process of change in size,

shape and form of insects Ametabola- no metamorphosis. No difference in

appearance as in adults except size. Egg – young- adult Hemimetabola – incomplete metamorphosis- egg – naiad

– adult Paurometabola- gradual metamorphosis- changes in form

are simple ; egg – nymph – adult Holometabola- complete metamorphosis – egg – larva –

pupa - adult

Complete Metamorphosis of Insect

Incomplete Metamorphosis

Insect Reproduction Bisexual reproduction – both male and

female required Parthenogenesis- there is no fertilization

hence there is no male needed Paedenogenesis- the larva is capable of

reporduction

Mode of giving birth Viviparity- live young are born Oviparity – eggs are laid, and left or

attended to hatch

Physical and behavioral adaptation of insects to the environment Protective coloration - camouflage or blending

with the color of the surroundings Mimicry – copying of other species for protection

Batesian mimicry – palatable insects resembles the appearance of a distasteful or poisonous insect

Mullerian mimicry – several distasteful insect species, often in unrelated families resemble each other

Wasmannian mimicry – mimics by being guest within the nest of other insects

Importance of insect to man and agriculture Beneficial Insects

Pollination Industrial products Food Scavenger Predators Use in medical and scientific research

Injurious Insects Damage crop directly or by transmitting diseases Destroy agri-products during storage Attack, parasitize and annoy and transmit diseases to domestic

animals and reduce theirs values

Why insects so successful Body structures

Exoskeleton Terrestrial forms- wax coating prevents desiccation Metamorphosis – immature insects and adults of a single species often exploit

different habitat Small size

Individual requires little food Escape from enemies dispersal

Adult flight Dispersal Escape from enemies Utilize new/different habitat

Reproductive capacity High reproductive capacity Short generation time

Different Insect Orders Order Archeognathans – bristletails Order Zygentoma/thysanura – silverfish Order Ephemeroptera – mayflies Order Odonata – dragonflies and damselflies Order Blattodea – cockroaches Order mantodea – mantids Order Isoptera – termites Order Grylloblatodea – mole crickets Order Dermaptera – earwigs Order Plecoptera – stoneflies Order Embiidina – webspinners Order Orthoptera – grasshoppers and crickets and katydids Order Phasmatodea – sticks insects

Continuation…. Order Zoraptera – Order Psocoptera – psocid and booklice Order Phthiraptera – lice Order Hemiptera – bug and leafhoppers Order thysanoptera – thrips Order Megaloptera – dobsonfly, alderfliy Order Raphidioptera – snakefly Order Neuroptera – lacewing, antlion Order Coleoptera – beetles Order Sterpsiptera Order Mecoptera – scorpionfly Order Diptera – flies Order Lepidoptera – butterflies and moth Order Trichoptera – caddisflies Order Hymenoptera - bees , wasp and ants

Crop Rotation Entomology Economic injury – the amount of injury which will give

significant loss once the economic plant part is affected Injury – effect of the pest activities on the host physiology that

is usually deleterious Damage – measurable loss of the host utility, most often

including yield, quantity, quality and or aesthetics Economic damage – the amount of the injury which will justify

the cost of artificial measures Economic injury level (EIL) – lowest number of insect that

will cause economic damage, or the minimum number of insects that would reduce yield equal to the gain threshold

Economic threshold level (ETL)- number of insects that should trigger management action.

Kinds of Pest Subeconomic pests – pest in the true sense even if they

cause significant losses. The General Equilibrium Population (GEP) is far below

Occasional Pest – GEP substantially below the EIL – more often does not cause economic damage though they are present in the field

Potential and Severe Pest – cause most serious and difficult problems in the field – key pest that attack the commodity directly mostly in numbers

Perennial pest – the GEP is below the ETL, but so close to the economic damage occurs more years than not

Severe Pest – have a GEP that is actually above the EIL, making them a constant problem

Biological Control Pest management tactics involving purposeful

natural enemy manipulation to obtain a reduction in a pest status

The use of living organism for the control of another organism

Natural enemies – living organism found in nature that kill insects outright, weaken them and thereby contribute to their premature death or reduced their reproductive potential

Nature of Biological control Disadvantages

Slow action Ecological problems Specificity Regulation and registration

Advantages Longer effect Effective Cheap specific

Agents of Biological Control Parasites – animal that lives on or within a larger animal.

Requires one host to complete its cycle Insect orders considered parasitoid

Coleoptera Lepidoptera Neuroptera Strepsiptera Diptera Hymenoptera

Predators – are free living organism that feed on the other animals, their prey sometime devouring them completely and usually rapidly

Major predators of insects Birds Fish Amphibians Reptiles Mammals Arthropods

Levels of Feeding Monophagous – narrow prey range, feeding

almost exclussively on a single species Oligophagous – narrow host range, feeding

only few prey species Polyphagous – tend to feed on a wide host

range

Examples of Parasitoids and Predators and their host Cotesia plutellae – Diamond backmoth larvae Diadegma sp. – Diamond Backmoth larvae Trichogramma evanescens – cornborer eggs Trichogramma chilones – earworm eggs Apanteles sp. Eggplant shootborer larvae Chelonus sp. – eggplant shootborer pupae Oencyrfus comperie – gren soldier bug eggs Telenomus pacificus – geen soldier bug eggs Ageniapsis citricola – citrus leafminer larvae Eucanthecona sp. – lepidopterous larvae Lady beetle – aphids adults and nymphs Tachinid fly – aphis adult and nymps Euboriella annulata – cornborer larvae Lycosa psuedoannulata – aphid, planthoppers, leafhoppers

Pathogenic Microorganism

Bacteria Bacillus popillae and B. lentimorbus – cause milky disease

of japanese beetle B. thuriengensis – causing disease in many species of

lepidopterous pest, mosquitoes and beetles Viruses

Nuclear polyhedrosis virus and Granulosis Virus cuase death of leppidopterous insect pest

Fungi Beauveria, Nomurea, Metarhizium, Entomopthora and

Zoophthora

Chemical Control Pesticide – any chemical use to control pest Advantages

Effective and rapid curative action Economical Ease of application Adaptable in most situation

Disadvantages Insecticide resistance Pest resurgence Negative impact to non-target organism Risks to users

Specific Pestcides Acaricide/miticide – mites, ticks and spiders Algaecide – algae Arboricide – trees, shrubs, bushes Avicide – birds Fungicide – fungi Herbicide – weeds Insecticide – insects Molluscicide – mollusks Nematicide – nematodes Pissicide – fish Predacide – vertebrate pest Rodenticide - rodents

Some insecticides that do not end with cide and not necessarily killing the pest

Attractants – attracts insects Chemosterilant – sterilized insects to prevent

reproduction IGR – stimulate or retard growth of insects Pheromone – release by one individual and affect the

physiology of others Repellant – repel insects

Classification of insecticide According to the nature and sources

Inorganic – lacking carbon Arsenic Cyanide Mercury Boric acid Sodium arsenate Sodium chlorate Copper sulfate

Organic- with carbon atom Natural – produce by refining natural substances Synthetic – manufactured by chemically joining elements or simple

compounds

Continuation…. According to the mode of entry Stomach – enters insect body through the gut Systemic – are taken up and translocated by

plants Contact – they usually enters the body when an

insect usually crawls with it. Absorbed through the body wall

Fumigants – insecticide that becomes gas and enters insect body through tracheal system, circulate and subsequently absorbed by the body tissue

Classification according to the chemical composition Chlorinated hydrocarbons/Organochlorines

DDT Lindane Cyclodienes polychloroterpenes

Organophosphates Malathion Dimethoate Disolfoton Dicrotophos Trichloroform Mathamidophos Acephate Parathion phosmet Methidathion Diazinon chlorpyriphos

Continuation …. Pyrethroid – resemblance of natural product cenerin from

pyrethrum Allethrin Resmethrin Fenvalerate Permithrin Cypermthrin Deltamethrin Lamda-cyhalothrin

Carbamates Carbaryl Carbofuran Aldicarb Methomyl propoxur

Continuation… Neonicotinoids resembles the natural products of

nicotine Botanical insecticides

Pyrethrum – from petals of chrysanthemum Azadiractina – neem tree Nicotine - tobacco Limonene – citrus peel Rotenone – Derris sp. Ryania – stems and roots of Ryania speciosa Sabadilla – seeds of Schoenocaulon officinale

Chemicals used with insecticides Synergist- enhanced toxicity of insecticide used Solvent – enhance solubility in water Diluents – carriers and are necessary to obtain proper

coverage of treated surface Surfactants - improves emulsifying, dispersing, spreading,

wetting and other modifying properties of the liquid Emulsifier – promote suspension of one liquid with the other Inert ingredient – inactive part of the pesticide Safener – counteract phytotoxicity effect of chemicals Spreader – facilitate creeping or spreading over a surface Sticker – increase adhesion

Types of insecticide formulation

Aqueous solution (AC) – homogenous mixture of 2 solution Emulsifiable concentrate (EC) – dissolved in small amount of

organic solvent when shaken with water emulsion is formed Water Soluble powders (WSP) – readily dissolve in water Wettable powders (WP) formulated as finely ground powder which

when mixed with water in the presence of a dispersing agent will form a suspension

Granules or pellets – active ingredients are combined with inert materials formed into particles. They are applied in dry form

Dust – Aerosols – active ingredient is suspended in a container under

pressure Flowable – the ingredients and deluent are ground to near colloidal

dimension, suspended a small amount of liquid

Host Plant Resistance Property of the plant that enables the plant to avoid, tolerate or recover from injury by insect population

that would cause greater damage to other plants of the same species under similar condition Advantages First line of defense Singular effective No serious disruptive effects on the environment Compatible with other control measures Inexpensive Safe Practical at low value crops Disadvantages Development of resistant varieties is tedious, expensive and long process Resistant cultivars may not be adoptive to certain localities Cultivars may be resistant to one but susceptible with other pest Resistant cultivars may easily breakdown Some resistant cultivars may have small effects

Mechanism of Resistance

Nonpreference – characteristic that lead away from a particular hosts for food, oviposition, or shelter (Antixenosis)

Allelochemic nonpreference – presence of chemicals

Morphological nonpreference – plant structural charateristics that disrupt physical condition of the pest

Antibiosis – refers to the deleterious effects on insects survival of life history resulting from feeding on a resistant host

Symptoms of insects affected by antibiosis Death of youngs Reduced growth rate Increase mortality in pupal stage Small adults Shortened life span Morphological malformation Restlessness and other abnormal behaviour

Tolerance Refers to the ability of a host to grow and

reproduce normally while supporting a pest population that would be damaging to a susceptible host.

Advantage Places no selective pressure on insect population.

Without selection pressure, variants do not develop that can overcome the resistance

Disadvantage Insect population may be allowed to sustain epidemics in

the area, causing problems in other crops

Other forms of resistance Ecological resistance – relies more heavily on environmental

condition Host evasion – the plant passes through a susceptible stage

quickly or at a time such that its exposure to potentially injurious insect is reduced

Induced resistance – form temporary resistance derived from plant condition or the environment

Host escape – lack of infestation of susceptible plants in a population of otherwise infested plants

Vertical resistance – refers to cultivars with resistance limited to one or few pest genotypes

Horizontal resistance – describes cultivars that express resistance against a broad range of genotype

Weed Science The study of weeds, and their control,

whether it is manual, mechanical, cultural, biological, chemical or ecological

Main goal – formulate the most satisfactory, most efficient yet least expensive method of controlling weeds

Weed – a plant out place in time and space

Characteristics of Noxious Weed Rapid vegetative growth and profuse root

production Reproduce early and efficiently Have the ability to survive and adapt to adverse

condition Seeds posses dormancy Cause significant damage even at low density Resistant to herbicide Adapted to competition

Importance of Weed Negative

Reduce yield of crops Increase costs for insect and diseases control Reduced quality of products Increases cost of production Reduces land value Exude chemicals that are harmful to other plants Imposed hazard to health

Positive Reduce soil erosion Food for animals and humans Prevent leaching of nutrients Important sources of useful drugs Sources of possible pesticides Provide germplasm for crop improvement Provide habitat for insect predator Authentic values

Classification of Weeds Based on morphological characteristics

Gross morphology Grasses – round and hollow stem, leaves aligned

in two rows Sedges – leaves aligned in three rows, stems are

solid and triangular Broadleaves – leaves may have various shapes

and arrangement of veins, leaves are wider than those of grasses and sedges

Body texture Herbaceous – soft, succulent Woody – hard texture

Based on life span Annual Biennial Perennial

Based on growth habit Vine Shrubs Trees

Based on habitat Terrestrial aquatic

Longevity of weed seeds Longevity – length of life or viability of weed

seed or vegetative propagules Highly affected by soil type, sunlight

exposure, cultural practices and moisture content

Seed dormancy Dormancy – is the inability of the seed or any

vegetative organ or tissue to germinate under favorable condition Primary dormancy –inherent property of the mature seed

as it leaves the parent plant Secondary dormancy – induced through encounter with

unfavorable condition Induced dormancy – develops when a non-dormant seed

becomes dormant after exposure to such specific environment condition

Enforced dormancy – limitations of the habitat or environment prevent seeds from germinating

Mechanism of dormancy Physical dormancy – impermeability of

water and or oxygen Physiological dormancy – immature embryo

or presence of inhibitors

Methods of breaking dormancy Microbial action or abrasive treatments:

sulfuric acid, stratification Passage through alimentary tract of

livestock Dehulling (physical dormancy) Alternate wet and dry conditions KNO3, GA3, cytokinins , Auxins Light and temperature treatment

Concept of Weed Germination Germination – resumption of growth by the

embryo in the seed or of the young plantlet in a tuber, bulb or rhizome

Phases of Germination Imbibition Period of rapid metabolic activity Root or root – like elongation phase Period of independent growth

Cultural factors affecting weed germination Water management Cultivation and light

Factors affecting seedling growth condition

Soil factor Light Adaptation to growing condition Competitive power of weed

Seed reporduction and dispersal Sexual reproduction

Annual weeds, usually reproduce by seed production

Factors affecting flowering and seed production Photoperiod Vegetative growth Temperature Growth regulators Magnitude of seed production

Asexual/ Vegetative propagation Principal means of propagation by most perennial weeds

Vegetative propagules Tubers Bulb Rhizome Stolon Runner Offshoot/suckers

Factors influencing asexual reproduction

Soil texture Daylength Light intensity Mineral sufficiency

Dispersal of weed propagules Methods

Dispersal unit – refer to the structure, usually single-seeded or multiple seeded together with accessory parts, that is disperse or separated from the mother plant asnd whose function is to perpetuate its kind in other areas

Agents of weed dispersal Wind , water , animals/man, explosive mechanism

of weed

Definition of terms on weed interference Competition – struggle for the limited

resources in the environment Critical period of competition – the length of

time wherein the crop is very sensitive to weed competition

Critical threshold level – the density of weeds above which yield reductions could be incurred

Types of competition intra- specific competition Inter specific competition

Factors affecting competition Weed species, density and duration of competition Seeding rate Crop variety or selection Level of nutrition

Major factors for competition Nutrients Water light

Methods of weed control Main purpose of weed management is to reduce

weed population to levels that will not significantly reduce crop yield

Methods of weed control Cultural

use of quality, disease and weed seed - free planting materials

Controlling weeds before reproductive stage Multiple cropping Water management Use of competitive crops

Manual Proper land preparation Handweeding/slashing Hoe weeding Interrow cultivation Mulching burning

Biological control method Deliberate use of weed natural enemies

such as insects and pathogens Types of biological control

Inoculative approach – use of imported living organism

Inundative or augmentative approach – use of very large numbers of existing and locally occurring natural enemies

Some bioherbicide De Vine – the first fungal pathogen

commercially made available in 1981 made of liquid formulation of Phytophthora palmivora

Collego – mycoherbicide commercially made available in the US in 1982 a dry powder of Colletotrichum gloeosporioides

Classification of Herbicide Based on time of application

Preplant herbicide – after land preparation but before planting Preemergence herbicide – applied after crop planting but before crop

emergence Postemergence – after emergence of the crop and weed

Based on movement in plants Contact herbicide – phytotoxicity is manifested on location where droplets

of herbicide are deposited Systemic or translocated herbicide – phytotoxicity is manifested at and

away from the site where droplets are deposited Based on selectivity

Non-selective herbicide – with broad spectrum activity that kills all Selective herbicide – kill some plants leaving practically others unharmed

Pesticide Calculation

Recommended rate (a.i/ha)

Amount of Pesticide x 100

a.i in the formulation

Herbadox 330E is applied at the rate of 1.25 kg a.i/ha to effectively kill R. exaltata. How many liters of Herbadox 330E do you need/ha?

Furadan 3G is applied at the rate of 0.5kg a.i./ha to control corn borer. How many kilograms of Furadan 3G do you need for 2,500 square meters?