1. ECOLOGICAL BASEMENT OF INTEGRATED PEST MANAGEMENT

2. 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.

3. Ecosystems & Pest Organisms
Ecosystem Organization & Succession
Definitions & Terminology
Trophic Dynamics
Limiting Resources & Competition

4. 1. Ecosystem Organization & Succession
Species : "groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups" (Ernst Mayr)
Individual: A single organism (bacterium, weed, nematode, insect); not always obvious.
Population : a collection of individuals of one species that exists in some defined geographical area
Guild: a group of species that exploit the same resource in a similar manner
Community: a group of populations occurring in the same geographical area
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).
Landscape: a cluster of interacting ecosystems

5. Landscape Ecology Crop Field Crop Field Crop Field Migration
Surrounding Ecosystem(s)
Extinction

6. 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.

7. 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

8. Lesson: Size AND distance both affect species equilibrium
Which is better?

9. 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.

10. 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:
Enforcement/implementation?

11. 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.

12. Natural tendency is to go to the right (cf Fig. 4-1 in text, p. 69)
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.

13. Fig. 4-1, p. 69

14. Implications of Early Succession Systems
Trophic cycles are disrupted (adds to the biodiversity problem)
Species good at invasion are favored
Nutrient cycles are altered, biomass does not accumulate/cycle
Energy flow is not webbed but, instead, directed toward one commodity
Ecology “resets” each cropping season

15. 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.”

16. 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)

17. General Concepts of Trophic Dynamics
What is a trophic system?

18. 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

19. 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.
BottomUp
Top Down

20. 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

21. 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

23. 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

24. 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.

25. r- vs. K-selected pests Characteristic r-Selected K-Selected
Reproductive Rate
High
Lower
Longevity
Short
Long
Competitive? No
Yes
Habitat
Disturbed
Stable
General Strategy
Invasive
Domination
Examples
Annual weeds, pathogens, nematodes
Perennials, mammals, some insects

26. Managing for one may help other
Characteristic
r-Selected
K-Selected
Reproductive Rate
High
Lower
Longevity
Short
Long
Competitive? No
Yes
Habitat
Disturbed
Stable
General Strategy
Invasive
Domination
Examples
Annual weeds, pathogens, nematodes
Perennials, mammals, some insects

27. 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.

28. 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

29. 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

30. Reading Assignment for Monday
Check the Reading Assignments page
Note the assignments that are covered in the exam
Chapter 8, pp. 172 – 208

31. Direct vs. Indirect According to Brown
(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

32. Direct Interaction (A + B) -> Outcome
Four possibilities B
Not 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
Not Crop Pest A
Crop Pest

33. Examples by Category
Green vegetable bug becomes a problem if provided with non-pest weeds.
Ants tending aphids.
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.

34. 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

35. 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).