Transcript Chapter_6_powerpoint--Dual_Listed_Course

Chapter 6
Plant Pests and Their Control
Anything that impairs the healthy growth
and maturation of a plant may be
regarded as an injurious agent.
 Some injurious agents cannot be
transmitted.
 Agents that can be transmitted from one
plant to another are regarded as either
infectious or infestious.
 An infected plant has the injurious agent
active within it.
 An infested plant has the agent active on
its surface.
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A parasite is an organism incapable of
manufacturing its own food.
 The parasitic insects, fungi, bacteria,
viruses, and nematodes, as well as the
weeds, are usually referred to as plant
pests.
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Entomology is the study of insects, their
effects on plants, and their control.
 Plant pathology is the study of plant
diseases, their causes, and their control.
 Bacteriology is the study of bacteria.
 Mycology is the study of fungi.
 Virology is the study of viruses.
 Nematology is the study of nematodes.
 Weed science is the study of weeds and
their control.
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Insects constitute over 2/3 of all the
animal species on the planet and are
surpasses only by microbes in sheer
numbers of individuals.
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In the animal kingdom, the major divisions
are known as phyla.
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The phylum Anthropoda contains the class
Insecta, or the insects.
The exoskeleton is the hard protective
covering of the insect’s body, and has
helped ensure survival of insects through
centuries of evolution and environmental
stress.
 The exoskeleton is composed principally of
chitin, a nitrogenous
polysaccharide compound
that resists water, alcohol,
acids, and alkalis.
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The mouthparts of insects determine how they
feed on plants and the symptoms of injury that
are manifested.
 Six common types of mouthparts:
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Chewing
Siphoning
Sponging
Rasping-sucking
Piercing-sucking
Chewing-lapping
The digestive system is a tube that
extends from the mouth of the insect to
the anus.
 The respiratory system combines
expansion and contraction of the abdomen
with diffusion to exchange oxygen and
carbon dioxide in the cells and tissues of
the insect.
 The nervous system is made up of groups
of specialized cells called ganglia and
nerve fibers that join the ganglia to other
parts of the insects body.
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No members of the animal kingdom transform
more dramatically during their development than
insects.
 The changes in insect form as they grow are
termed metamorphosis.
 Complete metamorphosis includes four stages of
development:
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Egg
Larva
Pupa
Adult
The effect of disease in plants is injury,
manifested in symptoms of abnormal
growth.
 The United States loses and estimated 1520% of the crop productivity each year
due to plant diseases.
 The most important causes of disease in
plants are the bacteria, fungi, viruses, and
nematodes.
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5 important characteristics of:
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Bacteria:
– Members if the plant kindom.
– Nonchlorophyllous
– Single-celled
– Three body forms (spherical or coccus, rodshaped or bacillus, spiral-shaped or spirillus)
– Reproduction by simple cell division.
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Fungi:
– Members of the plant kingdom
– Non-chlorophyllous
– Their vegetative body ranges in size from a
single cell to a thread-like multi-cellular
structure termed a mycelium.
– Reproduction by formation of spores.
– Classification is on the basis of life cycle,
specifically how the vegetative and
reproductive organs develop.
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Viruses:
– Their categorization as plants or animals is
undetermined.
– Non-chlorophyllous
– Composed of nucleic acids and proteins
– Smallest of the pathogens, visible only with
an electron microscope.
– Plant viruses appear most commonly in two
morphological forms: a long, narrow, tube-like
rod and an isometric polyhedron (shape with
many sides of equal length)
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Nematodes:
– Members of the animal kingdom
– Feed on both plants and animals.
– Plant nematodes average about 1 millimeter
in length.
– Body wall usually transparent, with an outer
covering termed cuticle.
– Feeding apparatus consists of mouthparts
equipped with buccal spear used to puncture
the host cell to with draw cellular fluids.
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Slugs and Snails:
– Members of the animal kingdom.
– Macroscopic in size.
– Nocturnal feeders on plant leaves and stems.
– Slugs lack the shell that is common to snails.
– Leave a slimy trail on the soil surface as they
move.
 Parasitic
seed plants:
– Weakly chlorophyllous but usually
incapable of meeting their own
nutritional needs.
– Connect to the vascular tissue of
chlorophyllous higher plants.
– Varying levels of parasitism:
 Epiphytic
 Hemiparasitic
 Fully parasitic
For a plant disease to occur there must be
a casual agent, the pathogen in the
vicinity of a susceptible plant, the host.
 The infectious form of the pathogen is
termed the inoculum.
 As long as the inoculum is only on the
host, the plant is termed infested.
 Once the pathogen is penetrated the
host’s tissues, the plant is termed
infected.
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Responses to pathogenic irritants and
insects are termed symptoms.
 Symptoms may be influenced by an
assortment of factors including:
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– Species of host
– Environment
– Quantity of inoculum or insects
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When fungi invade the tender stem tissue
of a young seedling, damping-off
develops.
Lack of light turns a plant yellow in a
condition termed etiolation.
 When the plant turns yellow but does not
lack light the symptom is termed chlorosis.
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Rotting results from a destruction of the host
cells that causes a release of the cellular fluids.
When tissue become desiccated or dried out and
dies, it usually turns brown or black, and is said
to be necrotic.
When all or part of the plant is reduced in size
as a result of pathogens (especially viruses),
insects, and nematodes it is termed dwarfing.
A reduction in cell size is termed hypotrophy.
A reduction in cell number is termed
hypoplasia.
A weed may be defined as a plant having
no positive economic value and/or
growing in a place where it is not desired.
 Weeds compete with other plants for the
materials both need to grow and thrive.
 Within a local area, weeds are distributed
as sees, stolons, roots, bulbs, rhizomes, or
tubers.
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Some natural agents of dissemination of
weeds:
– Flowing water
– Wind
– Birds
– Livestock and other animals
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Some artificial agents of dissemination of
weeds:
– Cultivating tools
– Vehicles
– Clothing
– Transplanting desired plants from one area to
another and moving weeds with them.
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Other causes of injury other than insects,
weeds, and disease:
– Rodents
– Lawnmowers
– People
– Vandalism
Quantitative damage- all or part of the
host plant is destroyed by the antagonistic
agent.
 Qualitative damage- host suffers a loss of
appearance and sale value.
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Three Levels of Pest Control:
Partial control- most common type; homeowner
may spray a broad spectrum (all-purpose)
pesticide and the plant may still show
symptoms, but not as severely as if the had not
been sprayed.
 Absolute control- is total control; all symptoms
of pest injury are absent.
 Profitable control- the level attained when
monetary returns on the crop exceed the cost of
the control measures.
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Partial control is the most common type of
pest control, but profitable control is the
most sought by growers.
 The determine the potential profitability of
a control measure, three factors must be
considered:
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– Value of single crop plant
– Ultimate value of the crop
– Average loss over a period of
years
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Exclusion- first principle of control; includes all the
measures designed to keep a pest from becoming
established in an area.
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Eradication- the principle that seeks to remove or
eliminate pests that are already in, on, or near
plants in infested areas.
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Protection- principle of control that sets up a barrier
between the host plants and the pests to which they
are susceptible.
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Resistance- fourth principle of control; attempt to
change the plant’s morphology and/or genotype so
that it will suffer less from diseases and insects.
When using pesticides, the choice of
formulation is based on:
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The size of the crop area being treated.
The amount of active ingredient being
applied.
The other materials being applied along with
the pesticide, such as other pesticides and
fertilizers.
Cost
Safety
Ease of application
The safe use of chemical pesticides
requires a respect for their toxicity.
 All manufacturers and distributors of
pesticides are required by federal law to
provide explicit information about their
products ingredients, formulations,
toxicity, and proper rates of application,
and about the specific pests controlled
and proper means of safe handling.
 Adjuvants- chemical additives that
improve the performance of the pesticide
with which they are combined.
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Integrated pest management (IPM) is a
multifaceted approach to pest control where one
may only use chemical pesticides only when
needed and applies the principles of control by
carefully balancing the relationship existing
among the crop hosts, the production
environment, and the plant pests to which the
crops are susceptible.
Plant extracts- chemicals found naturally in
certain plants; when extracted, concentrated,
and applied to vulnerable pests, these natural
chemicals can interfere with the growth and
development of certain pests.
 Microorganisms- can be used as antagonists
against other organisms include various species
of bacteria, fungi, protozoa, viruses, and
nematodes. They are applied to host crops
where they infect and destroy the target pest.
 Microbe-derived pesticides- use the natural
antibiotics and other compounds extracted from
microorganisms to control plant pests.
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Pyrethroids- synthetic version of the
natural extract, pyrethrins. They tend to
control a wider range of pests and remain
effective longer than the natural pyrethins.
 Soaps- light oils made from plants; works
against soft bodied insects by penetrating
their outer layer and dehydrating their
interiors.
 Insect growth regulators- disrupt the
growth and development of insects. The
effect is usually hormonal and interferes
with the metamorphosis of the insects.
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Chronicotinyls- similar to insect growth
regulators that act by impeding the
normal functioning of the insect nervous
system. They are systemic and can be
applied as either granulars or as sprays.
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Pheromones- chemical cues used by
insects to communicate; when
synthesized, sex pheromones can be used
as baits to attract and trap certain insects.
It is more useful as a management and
monitoring tool than a control measure.
Eight symptoms of injury following
infestation by insects:
Wilting
 Color changes
 Rotting
 Death of tissue
 Dwarfing
 Increase in size
 Tunneling
 Holes
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