Integrated Pest
Management
IPM
Reading Assignment:
Norris et al., Chapter 1. Pests, People, and
Integrated Pest Management. Pp. 1 – 14.
Define “Pest”
FIFRA Definition of “Pest”
(1) any organism that interferes with the
activities and desires of humans or (2)
any other form of terrestrial or aquatic
plant or animal life or virus, bacteria, or
other micro-organism (except viruses,
bacteria, or other micro- organism on or in
living man or other living animals) which
the Administrator declares to be a pest
under section 25(c)(1).
A Working Definition of “Pest”
An injurious and noxious or troublesome
living organism [that] does not include a
virus, bacteria, fungus or internal parasite
that exists on humans or animals (British
Columbia Pesticide Control Act,1997)
Includes insects, weeds, plant pathogens,
birds, non-human mammals and other
organisms which pose non-medical
problems to humans and non-veterinary
problems to animals
A pest must cause injury
In order for an organism to be considered a
pest, a damaging stage of the organism
must be present in high enough numbers
to cause actual injury to something valued
by people.
“Pest” is not a property of a species
Being a pest is not an inherent property of a
species but, rather, a species (along with
its population and age distribution at a
given time and place) and a human
valuation of the item being injured or
damaged.
Four things required to “make” a
pest (Fig. 1-6 from text)
1. Pest species must
be present at the
right stage
2. Environmental
criteria must be
met.
3. Crop must be a
susceptible variety
and growth stage.
4. All of the above
must occur at the
same time.
This is a pathosystem concept
• Pathogen – host – environnment triad
must all be right in order for an outbreak of
disease.
• When pest – crop – environment right,
leads to “damage”.
Pest damage to crops is significant.
From Fig. 1-9
How do pests become pests?
1. New crop introductions
2. New organism introductions
3. Production system practices
4. Removal of limiting factors
5. Low tolerance
The Pest Complex
• The specific collection of pest species
attacking a specific commodity or cropping
system at any given time and location.
• A given complex is divisible into different
“groups”:
– Invertebrates (arthropods, molluscs)
– Vertebrates (mammals, fish, birds)
– Weeds (perennials, summer/winter annuals)
– Plant Pathogens (fungi, bacteria, viruses,
nematodes)
Each pest species has a given
status within a complex
•
•
•
•
•
•
•
•
Key pests
Minor pests
Secondary pests
Occasional pests
Potential pests
Chronic pests
Migrants
Accessory Species
– Vectors (Pest status often linked with pathogen)
– Alternate Hosts
Pests are often classified by the
type of injury that they cause
General Terms
• Direct Pests
• Indirect Pests
• Medical/Veterinary
Pest Injury versus Damage
Injury – The effect that the pest has on the
crop or commodity.
Damage – The effect that injury has on
man’s valuation of that crop or commodity.
For crops, “Injury” is biological and
“Damage” is economic. For non-crops,
“Injury” = “Damage”.
Maximum Value
{
}
Economic Damage
Loss in value is great
enough to warrant
control action.
Value
Measurable
Damage
Working Concept for Damage
Injury
Organisms that cause economic
damage are the ones of interest in
pest management
Introducing “Pest Management”
• “Management” -- a process by which
information is collected and used to make
good management decisions to reduce
pest population impacts in a planned,
coordinated way.
• Requires:
– Tolerance
– Information
– Strategy
IPM Defined
IPM – A system that maintains the
population of any pest, or pests, at or
below the level that causes damage or
loss, and which minimizes adverse
impacts on society and environment.
Attempts to balance the benefits of pest
control actions with the costs when each is
considered in the broadest possible terms.
Balancing costs and benefits can
be done at various levels
T otal Cost to
F armer, Environment,
and Society
Cost of Using
All Available
T actics
Pesticide
Application
Cost
Benefits
T otal Benefit
to F armer and
Society
Impact on
Damage from
T otal Pest Complex
Pest
Damage
Avoided
Decreasingly Complex
Increasingly Comprehensive
Costs
The Pest Management Continuum
Pest Management at the Crossroads
See Handout.
Total US Crop Acreage
Distribution of US Cropland Over
the IPM Continuum
Source: Benbrook Consulting Services Analysis of Data in Adoption of IPM
in U.S. Agriculture, ERS/USDA, 1994
Cost to Farmer (Micro)
Cost to Society (Macro)
Limitation on IPM is Macro vs.
Micro Economics
No
IPM
Low
Medium
IPM Continuum
High
(Biointensive)
Proponents of one flavor often
attack other flavors
As an example, read the paper by Ehler &
Bottrell in the Reading Assignments for
Jan 14.
Come Prepared to Discuss
Two Basic Decision Categories in
IPM
Most Control Decisions Combine One of
Each of the Following:
1. Tactical vs. Strategic
•
•
Tactics – Individual control options
Strategies – Combinations of Tactics
2. Preventative (Prophylactic) vs. Curative
(Therapeutic)
•
•
Preventative – Before pest is a threat
Curative – When pest is threatening
Hypothetical Strategy
Preventative
Preventative
Rescue
Implement
Tillage Tactic
Conserve
Biological
Controls
Apply
Insecticide 2
if neccessary
Tactics
IPM Strategies are Implemented
Via Programs
• Programs include pest monitoring and
decision tools
• Monitoring & decision tools tie into the
strategy.
Strategy vs. Program (Strategic Plan)
Strategy
Pest Management Program
Implement
Tillage Tactic
Implement
Tillage Tactic
Conserve
Biological
Controls
Conserve
Biological
Controls
Weekly Count
Insect A
Caterpillars
Too Many
Caterpillars?
Apply
Insecticide 2
if neccessary
Yes
Apply
Insecticide 2
No
The Evolution of IPM
• Pest management is at least as old as
agriculture.
• It has evolved along with agriculture and
technology
• Generally, when technology as advanced, so
has pest management (and vice versa).
• Read Chapter 3 in text: Historical
Development of Pest Management. Pp. 47 64
Four Logical Periods
• Before WWI
• Between WWI & WWII
• Between WWII & 1962 (Silent Spring)
• 1962 onward
Before WWI
• Periods of great advancement followed by
decline.
• Advancing periods characterized by:
– Scientific inquiry into the nature of crops and
pest biologies
– Agricultural production for profit, specifically,
for well-developed export markets.
Early Examples
4,000 – 5,000 BC
Early China
2,500 BC
Summerians
1,000 BC
Egyptians
400 – 200 BC
Greeks
200 BC – 100 AD
Romans
1500 – 1700 AD
Baconism
Major Events in Baconism
•
•
•
•
•
•
•
Voyages of Discovery
Printing & Woodcuts
Perspective in Art
Microscope Invented
First Naturalists
Agricultural Markets Develop
Scientific Method
During the 19th Century
• Great strides in biological knowledge (e.g.
germ theory, evolution, genetics).
• Industrial revolution leads to large scale
farming and commercial markets
• Modern pest groups are recognized
(insects, weeds, pathogens)
• Potato famine creates incentive for
government funding of pest controls.
19th Century Pest Control
Advances
• Pressurized spray equipment nozzles
invented
• First modern success in biological control
• First modern success in host plant
resistance
• Modern cultural tools developed
• Most key pests’ biologies understood
By WWI
• Modern pest tactics were available but
only a few were practical.
• Developed countries were being invaded
by major foreign pests.
Between WWI & WWII
Pest Control Depended on Relative Crop
Value
• High Value Crops – Became pesticideoriented: Improved equipment and
chemicals
• Low Value Crops – Managementoriented. Emphasis on plant breeding,
cultural methods, basic science & ecology
During the 1940’s
• 1940 – DDT patented as an insecticide
• 1942 – BHC found insecticidal
• 1943 – 2,4-D found effective as a
herbicide
• 1946 – Gerhard Schrader hired by Bayer
• 1946 – Houseflies found resistant to DDT
During 1950’s
Organic chemical pesticides become routine
on all crops
• Viewed as “modern” farming
• Low risk, “cost of business”
• Few/no regulations
• High prices/demand for US exports
• Problems would not be addressed until
1962
Problems Arising During the 1950’s
• Pest Resistance
• Bird/Fish Kills
• Human Poisonings
• Secondary Pests
• Biomagnification
“Pesticide Treadmill”
1. Spray, kill pest & natural controls. Pest
comes back. Repeat until…
2. Resistance in primary pest. Increase
application rates. Kill broader range of
natural controls.
3. Induce secondary pest
4. Begin spraying for secondary pest until…
5. Resistance in secondary pest
6. Change chemicals. Repeat sequence.
IPM Evolution Continued
Reading Assignment
Norris et al. Chapter 2. Pests and Their
Impacts. Pp. 15 - 45
Silent Spring in Context of its Time
In the 10 years before Silent Spring…
• Many new innovations were introduced.
Pesticides were viewed as one of them.
• Widespread attitude was that man could
control nature. Pesticides were a
manifestation of that view.
• After the depression & war, people wanted
to believe that the govt & corporations
could be trusted.
Silent Spring Coincided with Other
Events
• 1962 – John Glen’s first orbital flight.
• 1962 – Thalidomide taken off market
(problem identified 11/61, public outrage
throughout 1962).
• 1962 – Cuban Missile Crisis
• 1961 – 1963 – MLK’s movement climaxes
• 1961 – 1963 – US increased presence
from 900 to 16,000 in Viet Nam
• 1963 – JFK assassinated
Silent Spring Aftermath
• 1963 – President’s Science Advisory
Committee issues report calling for
reducing pesticides’ effects.
• 1963 – Senate calls for creation of
Environmental Protection Commission
• Early – mid ’60’s – Increased sensitivity in
analytical equipment enables detection of
ppb’s. Including other chemicals.
• 1965 – First pesticide food tolerances
As the Effects Spread …
• Public became increasingly negative
toward chemical companies.
• 1970 – EPA established.
• 1972 – DDT banned (biomagnification)
• 1973 – IBP project started
– Emphasized pest control as a system
– Introduced pest modeling/decision tools
– Only for insects
IPM Concept Solidifies in the
1970’s
• 1975 – First textbook, Metcalf & Luckman
(former had been criticized in SS)
• 1978 – CIPM project replaces IBP
– Included weeds & plant pathogens
– Included economic analyses
• 1978 – KY statewide IPM program began
IPM Becomes Ingrained
• 1984 – IPM becomes an annual federal
budget item
• Large-scale scouting programs rise,
decline, and stabilize in the 1980’s
• 1993 – National IPM Initiative: 75 % of US
cropland to have IPM by 2000
• 2000 – National effort to develop “Crop
Profiles” and “IPM Strategic Plans”
Current Status
• IPM widely recognized as the proper
approach to dealing with pests in
production agriculture.
• Implementation is up to individual farmers
so it varies considerably
• Concepts are well established but the
technology continues to improve.
Significance of Pests in IPM
By Wednesday, Read Norris et al. Chapter
5, Comparative Biology of Pests
Impact Related to Direct & Indirect
Effects
Comparison of Direct and Indirect Pests
Characteristic
Direct
Indirect
Commodity
Yield-Pest
Relationship
Marketable
Non-Marketable
Simple
Complex
Pest Status
Usually Key Pest
Any
Pest Group
Insects &
Pathogens
Any
Farmer Tolerance
Low
Higher
General Impact of Pests -- Injury
•
•
•
•
•
•
•
Consumption of plant parts
Chemical toxins, elicitors, and signals
Physical damage
Loss of harvest quality
Cosmetic damage
Vectoring of pathogens
Direct contamination
General Impact of Pests – Noninjury
• Costs incurred to implement controls
• Environmental and social costs
• Regulatory costs (embargoes,
quarantines, shipment costs, etc.)
Crop Injury in More Detail
• Crop Injury
– Tissue Injury
•
•
•
•
•
Leaves
Structural
Roots
Flowers and Fruiting/Reproductive Tissues
General Systemic Injury
– Weed Effects
• Competition for Water, Light, Nutrients
• Allelopathy
• Other Economic Effects
Tissue Injury to Leaves
Abscission -- Leaf prematurely dropped by the plant, often while still green.
Tissue Injury to Leaves
Bleaching Leaf turns white or nearly so. Usually caused by using the wrong
herbicide.
Tissue Injury to Leaves
Chlorosis Leaf tissue loses its chlorophyll and turns yellow. May
occur in spots.
Chlorosis in soybeans. Individual leaves (left) and at the field level (right).
Tissue Injury to Leaves
Crinkling Leaf takes on a crinkled texture. Usually associated with viruses
or toxic effects of saliva from homopterous insects.
Crinkling may occur throughout the leaf (left) or may be confined to edges (right).
Tissue Injury to Leaves
Cupping and Curling Leaves cup up or down or they curl inward from the edges.
Downward cupping along main vein of each leaflet in soybeans caused by
Bean Common Mosaic Potyvirus
Tissue
Injury
to
Leaves
Edge Feeding Leaves chewed and eaten from the edges. Feeding lesions can
have smooth or jagged edges. Usually caused by insects w/chewing mouthparts.
Leaf edge feeding on rhododendron leaves by adult black vine root weevils.
Tissue Injury to Leaves
Hole Feeding Leaves have holes chewed through them. Caused by insects
w/chewing mouthparts.
Yellow poplar weevil adult feeding on yellow poplar
Tissue Injury to Leaves
Mines Caused by small, immature beetles or flies that live in-between the upper
and lower leaf surfaces. The shape of the mine, along with the plant species
being attacked, is useful in identifying the pest species involved.
Frass-linear
leaf mine on
birch leaf.
Mines come in
many shapes.
Tissue Injury to Leaves
Mottling Leaf is not uniform in color but is, instead, a mottled mixture of
different shades of green to yellow.
Soybean leaf mottling caused by the Bean Pod Mottle Virus.
Tissue Injury to Leaves
Necrosis Areas of dead tissue which usually sloughs off over time.
Necrosis simply means dead
tissue and may occur in any
pattern. Necrosis may be in
spots (top left), on leaf margins
(above), or follow leaf veins
(bottom left). Other patterns are
possible as well.
Tissue Injury to Leaves
Rolling Leaf is rolled up like a cigar. Usually caused by caterpillars
that use the rolled leaf as a pupation chamber.
Leaves may be rolled entirely (above) or only
partially (left).
Tissue Injury to Leaves
Shothole Small holes in a straight line across the leaf. Usually caused by
insects that bore through the developing leaf when the un-emerged leaf is
still rolled up in the plant’s whorl.
Tissue Injury to Leaves
Skeletonization Leaf tissue between the veins is removed but the veins
remain intact leaving a skeleton-like appearance.
Lindin leaf skeletonized by Japanese
beetle. Note that the distal leaf tissue
is relatively normal looking indicating
that the leaf veins are fully functional.
Tissue Injury to Leaves
Spots Caused by fungal, bacterial, and viral diseases. Spots vary in size, shape
and number and may be solid or only peripheral (e.g. ring spot, frog-eye spot).
Fungal leaf spot on soybean
Bacterial leaf spot on pepper
Viral ring spot
on purple cone
flower
Tissue
Injury
to
Leaves
Stippling Large numbers of tiny pin-prick feeding lesions cause by mites or
other minute herbivores with piercing-sucking mouthparts.
Leaf stippling by leaf hoppers (sucking insect). Non-uniform pattern. Stippling
= dead cells surrounding feeding puncture.
Tissue Injury to Leaves
Windowpaning One side of the leaf is scrapped off leaving the other
side intact and translucent. This gives the feeding lesion a window-like
appearance. Primarily caused by some young beetle and moth larvae.
Cereal leaf beetle windowpaning on
wheat (left); European corn borer
windowpaning on corn (right).
Structural Tissue Injury
• Galls (may be on any tissue)
• Interference with transport
– Xylem injury
– Phloem injury
• Interference with structural support
• Shape/appearance impact
– Abnormal growth
– Shoot dieback
Galls
Can occur on all
tissues; leaves,
stems/trunks,
branches, roots, etc.
Ash flower galls
caused by a mite
Olive knot gall
(caused by
Pseudmomonas
bacteria) on olive
main trunk
Galls on oak leaves from
cynipid wasps
Western gall rust on
Ponderosa pine branch
Soybean roots with galls from
root knot nematode (right) vs.
healthy root (left).
Structural Tissue Injury -- Xylem
Many insects, such as the
squash vine borer feed on
xylem tissue.
Tomato wilt is caused by fungi in
the genus Fusarium which plugs
xylem tissue preventing
water/mineral transport.
Structural Tissue Injury -- Phloem
Bark beetle gallery (right): The adult Beetle lays a
line of eggs along a gallery. The grubs hatch, eat
phloem tissue until they mature.
Phloem discoloration by San Jose
scale on apple.
Phloem discoloration and necrosis
caused by spiroplasma infection.
Structural Tissue Injury –
Interference with Structural Integrity
Stalk breakage (lodging) caused by fungal stalk rot (left) and European
corn borer (right)
Structural Injury – Abnormal
Growth
Many plant pathogens and some
insects cause abnormal growth in
plants. Common forms are called
rosettes (above) and witch’s
brooms (right).
Root Injury – Fibrous Roots
Varying degrees of corn rootworm injury (left) and resulting lodged plants (right)
Phytophthora
root rot on
alfalfa (left);
Fusarium
root rot on
soybean
(right)
Root Injury – Storage Organs
Black rot on carrot (left), nematode injury to carrots (middle), carrot weevil injury (right)
Flower & Fruit Injury
Apple scab
on apple
(right)
Codling moth in apple
Left: Western
flower thrips
feeding injury
on impatiens.
Above: Bean pod mottle virus in soybeans
(left) vs. uninfected beans (right)
Weed Effects
•
•
•
•
•
Weed Groups
Algae (aquatic systems)
Mosses/liverworts (turf & nurseries)
Ferns/horsetails (pastureland, horticultural
crops)
Gymnosperms (rangeland, forests, long-term
no-till systems)
Angiosperms [monocotyledon & dicotyledon]
(annuals, biennials, perennials)
Weed Impacts
• Competitive -- yield loss (quantity and
quality)
• Parasitic effects (cf Norris et al., p 23 – 24)
• Mechanical interference with farm
implements
• Other incidental
– Seed contamination
– Land valuation
– Health & safety (hay fever, toxins, fire hazard)
Comparative Biology of Pests
Chapter 5 is divided into 3 principal segments
1. Concepts in Pest Population Regulation
2. Dissemination, Invasion, and Colonization
Processes
3. Pest Genetics
Comparative Biology of Pests
•
Concepts in Pest Population Regulation
1.
2.
3.
4.
5.
6.
7.
8.
9.
Reproduction
Fecundity & Fertility
Population Generation Time
Longevity & Mortality
Quiescence and Dormancy
Heat Summation & Degree Days
Molting & Metamorphosis
Life Tables
Basic Life Cycle Models
1. Reproduction -- “Vivipary”
In Plants
Flowers are replaced by tiny
plantlets which detach and
grow into new plants. A form
of asexual reproduction.
These plants grow where
there is a short growing
season or where it is shady
with few pollinators. This
example is a wild onion
Allium, where the flowers in
the umbel inflorescence are
replaced by vegetatively
produced bulblets (little
bulbs), and these bulblets
sprout on the parent plant.
1. Insect Reproduction
Oviparity -- Eggs deposited shortly after fertilization
Ovoviviparity -- Female deposits a larva or nymph instead
of an egg
Viviparity -- Female feeds embryo after development has
begun
Paedogenesis -- Larvae give birth without becoming an
adult
Parthenogenesis -- Development without fertilization
Polyembryony -- A single egg results in more than one
individual
1. Reproduction
Sexual
Good for IPM
Bad for IPM
1.
Can manage
resistance
Mating disrupt.
possible
More plastic, better
able to overcome
tactics
Strain/race
geographically
specific
Can’t overcome
effective controls
1. More inoc. (path &
weed)
2. Faster popn.
growth (all are
reproductive)
2.
Asexual
1.
2.
Note: Many serious species have both sexual & asexual periods or stages.
Individual and Population
Development Time
•
Includes:
2. Fecundity & Fertility
3. Population Generation Time
4. Cycles per Season – note terms in Norris et
al., p. 99.
5. Longevity and Mortality
•
Affects management response time
Understand Generic Life Cycles
Many insects, some
pathogens &
nematodes, many
mammals, summer
annual weeds
Some insects,
some mammals,
most winter
annual weeds
Many nematodes,
multivoltine arthropods,
polycyclic pathogens,
small mammals.
Weed seedbanks,
some pathogens,
cyst nematodes
Ecological Basis for Pest
Management
Part I. Ecosystems and Pest
Organisms
Ecological Basis for Pest
Management
This is a 4-part unit:
• Part I -- Ecosystems & Pest Organisms
• Part II -- Ecology of Interactions of Pests
• Part III -- Ecosystem Biodiversity and IPM
• Part IV -- Applying Ecological Principles to
Managing Pest Populations
Assignment for Friday, Feb. 6
Find an article (preferably online) that applies an
ecological principle to pest management. Hand
in one page containing a copy of the abstract of
the article (with title and reference) and a brief
description of the article and how an ecological
principle was applied to a pest management
problem. Identify which of the three ecological
chapters from the text (Chap. 4, 6, or 7) your
article most closely relates. We will group the
articles by chapter and everyone will make a 2-3
minute presentation on his or her article.
Why Study Ecology in IPM?
• History of IPM is a history of applied
ecology
• Managing pests often relies on exploiting a
pest’s ecological weaknesses.
• Alternatively, one may manage the
ecology in order to make a crop less
vulnerable to pests.
• Future of IPM lies in increasingly
sophisticated ecological manipulations.
Ecosystems & Pest Organisms
1. Ecosystem Organization & Succession
2. Definitions & Terminology
3. Trophic Dynamics
4. Limiting Resources & Competition
1. Ecosystem Organization & Succession
1. Species : "groups of actually or potentially interbreeding natural populations that
are reproductively isolated from other such groups" (Ernst Mayr)
2. Individual: A single organism (bacterium, weed, nematode, insect); not always
obvious.
3. Population : a collection of individuals of one species that exists in some defined
geographical area
4. Guild: a group of species that exploit the same resource in a similar manner
5. Community: a group of populations occurring in the same geographical area
6. Ecosystem: a community of living organisms and the abiotic framework that
supports them. Agroecosystem – An ecosystem dominated by humans that
typically has few common or major species (crops) and numerous rare or minor
species (some of which are pests).
7. Landscape: a cluster of interacting ecosystems
Landscape Ecology
Crop
Field
Crop
Field
Crop
Field
Migration
Crop
Field
Extinction
Crop
Field
Surrounding
Ecosystem(s)
Landscape Ecology
• Involves multiple populations interacting in
time and space between several different
ecosystems.
• “Blinking Lights” Theory
• Often presented as an application of
“Island Biogeography” -- Concentrates on
local population/species extinctions.
Island Biogeography & Landscape Ecology
Wilson & MacArthur studied species extinction rates on
small islands & found:
• When one species goes extinct, it is replaced so
that there’s an equilibrium
• Replacement species is not necessarily the
same as the extinct population…may be another
from the same guild.
• Smaller islands have higher extinction rates than
larger islands.
• Extinction rates increase with increasing
distance between islands
Lesson: Size AND distance both
affect species equilibrium
Which is better?
Lesson: Agroecosystems can
fragment landscapes
• Some species are stranded on their
islands – increasing the chance that they
might go locally extinct.
• Reduction in biodiversity is good for pests
which thrive in the agroecosystem anyway.
• Note that reduction is in species diversity –
includes number of spp. AND number of
individuals.
Green Network Concept
• Maintain a network of contiguous patches
& corridors that are not part of the
agroecosystem.
• Specific Things to do can be found at:
– http://www.dal.ca/~dp/reports/zkidston/kidston
st.html#guidelines
– http://www.dal.ca/~dp/reports/zkidston/guideli
nes.html
• Enforcement/implementation?
Ecological Succession
• An orderly, directional and therefore predictable
process of development that involves changes in
species structure and community processes
over time.
• Results from a modification of the physical
environment by the community and culminates
in a stabilized ecosystem in which maximum
biomass and symbiotic functions are maintained.
Succession Sequence
Natural tendency is to go to the right (cf Fig. 4-1 in text, p. 69)
Agriculture
typically keeps
the ecosystem at
this end.
Fig. 4-1, p. 69
Implications of Early Succession
Systems
1. Trophic cycles are disrupted (adds to the
biodiversity problem)
2. Species good at invasion are favored
3. Nutrient cycles are altered, biomass
does not accumulate/cycle
4. Energy flow is not webbed but, instead,
directed toward one commodity
5. Ecology “resets” each cropping season
2. Definitions and Terminology
Refer to pp. 71 – 72 in text. Notes on those definitions:
• Carnivores and Omnivores can be monophagous,
oligophagous, or polyphagous
• Host organisms do not necessarily host parasites,
herbivorous insects also feed on “hosts”
• Note distinction between parasites and parasitoids.
Both can be internal or external (ectoparasites).
• Add “Pathogen – A microbial parasite that causes
disease. Primary – attacks a healthy host,
secondary – attacks an injured/weakened host.”
3. Trophic Dynamics
Large subject that is central to pest injury
and pest management.
• General Concepts
• Bottom-up versus top-down processes
• Basic food chains – note the diagrams
– Pathogens
– Weeds
– Webs (generalized and animal-based)
General Concepts of Trophic
Dynamics
What is a trophic
system?
Top-Down vs Bottom-up Trophic
Systems
• Top-Down – Producers (plants) limit the
growth of primary consumers (herbivores)
which limit the growth of primary
carnivores & so on.
• Bottom-up – Top consumers limit growth at
the next lowest level throughout the chain.
• Note that “limit” can be an economic
effect, not necessarily an ecological one
Top-Down vs Bottom-Up Trophic
System
With bottom-up
control, increased
production results in
greater productivity at
all trophic levels.
With top-down
control, consumers
depress the trophic
level on which they
feed, and this
indirectly increases
the next lower trophic
level.
Bottom
Up
Top
Down
Grazer vs. Decomposer Systems
Grazer food chains
begin with algae and
plants and end in a
carnivore.
Decomposer chains are
composed of waste and
decomposing organisms
such as fungi and
bacteria
Food Webs
• Two or more trophic systems linked within
a given ecosystem or landscape.
• Three main categories in agroecosystems:
– Animal-based (animal production systems)
– Above-ground, plant based (Crop Production
Systems [CPS])
– Soil food web in CPS’s
• The two CPS webs interact but are usually
managed separately
Components Soil Food Web
Pest/weed biocontrol components in red
• Herbivores – Root feeders (arthropods,
microbes)
• Pathogens – Microbes that attack underground
organisms
• Shredders – Chew up organic matter, increasing
surface area & decomposition rate
• Decomposers – Decompose organic matter
• Predators – Maintain stability of above
populations
Limiting Resources & Competition
• Populations can be limited in several ways
– Food & water
– Shelter/Reservoir
• Limitation can occur at any stage or time
(e.g. overwintering)
• Effectiveness dependent on population
ecology of individual pest. Life history
strategy important part of that ecology.
r- vs. K-selected pests
Characteristic
Reproductive
Rate
Longevity
Competitive?
Habitat
General
Strategy
Examples
r-Selected
High
K-Selected
Lower
Short
No
Disturbed
Invasive
Long
Yes
Stable
Domination
Annual weeds,
pathogens,
nematodes
Perennials,
mammals,
some insects
Managing for one may help other
Characteristic
Reproductive
Rate
Longevity
Competitive?
Habitat
General
Strategy
Examples
r-Selected
High
K-Selected
Lower
Short
No
Disturbed
Invasive
Long
Yes
Stable
Domination
Annual weeds,
pathogens,
nematodes
Perennials,
mammals,
some insects
Interactions Between Pest
Categories
Read Chapter 7, Ecosystem Biodiversity & IPM
Fig. 6-1, p. 129
Note: No crop,
management,
beneficial species,
or environmental
effect. Biological
interactions
between pests
only.
Interactions Between Pest
Categories
•
•
•
•
Trophic Relationships
Environmental (Habitat) Modification Result
Mechanical Effects
Response to Control Tactics
– Non-pesticide
– Pesticide-related
• “Interactions” may be:
– Pest-pest or pest-crop
– Measured in injury or damage
This subject excludes the direct
effects of:
• Interactions within pest categories (i.e. –
pathogen – pathogen). But note that
viruses, bacteria, fungi, & nematodes are
different “categories” for Norris et al.
• Interactions between pests and their
natural enemies
Reading Assignment for Monday
1. Check the Reading Assignments page
•
Note the assignments that are covered in
the exam
2. Chapter 8, pp. 172 – 208
Direct vs. Indirect According to
Brown
• Direct:
(Pest A + Pest B) -> Outcome
– Outcome may be biological or economic
– If Spp. A & B are present, outcome is realized
• Indirect:
Pest A -> Affector -> Pest B -> Outcome
– “Affector” may be another pest, management action,
environmental effect, etc.
– A & B & Affector must all be present for outcome to
occur
Direct Interaction
(A + B) -> Outcome
Four possibilities
B
Not Crop Pest
Not Crop Pest
A
Crop Pest
Crop Pest
1 – Together, one
(or both) pest
2 – A helps B
3 – A needs B
4 – A and/or B
are worse
together
Examples by Category
1. Green vegetable bug becomes a
problem if provided with non-pest weeds.
2. Ants tending aphids.
3. Weeds as alternate hosts for pathogens.
Overwintering hosts for aphids.
4. cf. item 4 on p. 136 (cutworms & chinch
bugs) & item 5 on p. 137 of text.
Read these sections closely
• Habitat Modification – Understand and be
able to ‘compare & contrast’:
– Altered Resource Concentration
– Altered “Apparency”
– Microenvironment Alteration
• Interactions Due to Physical Phenomena
– Physical Damage to Host
– External Transport
– Internal Transport
Ecosystem and Biodiversity in IPM
• Why did monocultures become so
widespread?
• Can we expect monocultures to continue?
• If so, how can we make biodiversity
relevant? At what spatial scale will this
relevancy be realized (cf. p. 157).
Frequent Disadvantages of
Biodiversity in CPS
Contrast with benefits noted on p. 158
1. Increasing plant diversity decreases density of
marketable commodities
2. Increased density/diversity of herbivores (cf. p. 136 –
137)
3. Increased alternative hosts for pathogens
4. Larger complex of species to be managed
5. More complex production system/equipment needed to
deal with mixed plantings
6. Dilution of inputs (fertilizer, water)
7. Decreases in commodity quality common (size, color,
texture, etc.)
8. Increased cost of commodity as a result of the above
Two Issues Must Be Resolved in a
Biodiversity & IPM Discussion
1. A. Does the discussion concern the use of
biodiversity in IPM or B. does it concern the
use of IPM to maintain biodiversity?
•
If A, emphasis is biocontrol, if B, emphasis is
pesticide reduction
2. A. Does the discussion concern managed
biodiversity within crop fields or B. does it
concern associated biodiversity in surrounding
ecosystem?
•
If A, emphasis is on tillage & cropping systems, if B,
emphasis is on landscape ecology.
4. Applying Ecological Principles to
Managing Pest Populations
• IPM is an implementation vehicle for
ecological knowledge.
• Degree of implementation varies, recall
the IPM continuum.
• Many examples available, see reading for
“A Whole Farm Approach to Managing
Pests.” In particular, note the sidebars.
Implementation of Ecological
Principles in IPM
• Goal is preventative – keep pest
populations from causing damage.
• Requires increased knowledge,
observation, management – Increased
costs not immediately offset
• Must return multiple benefits for adoption
• Usually helps, seldom adequate in itself
Two Approaches to Using
Ecological Knowledge in IPM
• Ecologically-Based Pest Management
(EBPM). Established in the NAS book of
the same name.
• Farmscaping – Mostly for biological
control.
• Widely used in organic production systems
Ecologically—Based Pest
Management
• Basic Ideas:
– Refocus pest management on maintaining ecological
balance
– Change management emphasis from individual
species/components to processes, interactions
between multiple species
• 3 Basic Principles
– Safety
– Durability
– Profitability
EBPM Status
• Much research is funded annually
• Profitability issues remain, EBPM systems
often not as profitable or are too risky
compared to existing IPM systems
• EBPM generally relies on collective efforts
(e.g. cooperatives, public oversight, etc.)
which have yet to be accepted on a wide
scale.
Farmscaping
• The practice of designing and maintaining
habitats that attract and support beneficial
organisms, used to improve crop
pollination and to control pest species.
• Emphasis on landscape ecology for
targeted objectives.
• Many examples are available. Here are a
few.
Many similar themes along these
lines
Here’s a small sample. Follow the links to
read a little about each one & get the idea.
• Permaculture
• Biointensive Pest Management
• Regenerative Agriculture
• Biodynamic Agriculture
Notes on First Hour Exam
• Scheduled for Monday, Feb. 23
• Covers everything through this point
–
–
–
–
Chapters 1 – 7 in text
All assigned reading
Lecture notes
Be sure that you can do the exercises
• Structure will be short answer (~2/3 of grade), longer
answer (most of the rest). Might be some matching.
• Note that the course has been re-organized since last
time so old exams are helpful only for structure.
• Exam starts promptly at 8:00 & papers are collected at
8:50.