Biocontrol Ideal - Integrated Pest Management - Lecture Slides, Slides of Pest Management

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Biocontrol Ideal

EIL

Population Density

Time

Biocontrol agent introduced Pest

Biocontrol Agent

Cropping System Characteristics

Conducive to Biocontrol

• Stability
• Abiotic environment supports NE’s
  • Temperature, moisture & shelter are all available as needed by NE
  • Soils support soil-based NE’s
• Biotic environment supports NE’s
  • Alternative food sources available
  • Food for all life stages available
• Management practices compatible
• Crop should have some damage tolerance

Pest complex characteristics

conducive to biocontrol

• Few species in the target niche
• Stable species composition
• Few key pests, few direct pests
• Ideally, minor pest species can act as

alternate hosts/prey

Note the benefits of biocontrol, pp 338 - 339

Costs/Disadvantages of Biocontrol

• Usually requires change in management practice
• Increases scouting effort
• Intrinsic time delay
• Increased risk
  • New NE’s may cause harm
  • Uncertainty about NE requirements/reliability
  • Always a potential for pest to escape control
• Fundamentally incompatible with other control tactics

Common Trade-off Quesitons

• Generalists vs. specialists.
• Multiple vs. single biocontrol species

Generalists vs. Specialist NE’s

• Disadvantages of generalists:
  • Usually have lower numeric response
  • Kill fewer pests/unit time/NE
  • May be attracted to other species
• Advantages of generalists:
  • Better survival when pest population is low
  • More likely present at pest establishment
  • Multiple generalist species can co-exist as a community (greater stability & reliability)

Pest Max

Elementary Implications of the

phase plane

Natural Enemy Population

Pest Population Must be < EIL

Stable -- Good Too Many Pests, Two Few NE’s

• Pests Have Escaped Control

Too Few Natural Enemies -- Pest Resurgence Danger

NE Max

NE Min

Pest Min

Too Many NE’s for Pest Pop. – NE Crash Imminent

Outcome Uncertain – Probably Bad

The “good” area often identified in

decision guides as NE/pest ratios

Spider Mite Examples

• Predator mite/pest mite (spider mite) on

apples must be at least 1:10 in

Washington raspberries.

• In N. Carolina apples:
  • 1 Predator mite/18 pest mites
  • 25 Coccinellid predators/5 trees
• European red mite in W. Virginia orchards
  • If mites > ET, no spray if predator/mite > 2.

Types of Biological Control

• Classical – Use of NE taken from native home of a foreign pest. Release once.
• Inoculative – Release occasionally. Builds up, controls pest, then dies out & must be re-introduced.
• Augmentative – Add to existing population as needed.
• Inundative – Flood area with NE. Not persistent. Similar to pesticides.
• Competitive Exclusion – Mostly applies to use of hypovirulent pathogen strains out competing virulent strain.
• Conservation – Avoid harming existing NE complex.
• Suppressive Soils – In some soils, pest (usually a pathogen) does not cause much damage.

Points on NE Conservation

• Judicious pesticide use
• Reduce other mortality caused by other

management activity

• Control secondary enemies
• Manipulate host plant attributes
• Provide NE’s ecological requirements
• Genetic enhancement of NE

Biocontrol Conclusion

• Read to examples of biocontrols in the text
• Evaluation of NE effectiveness
  • Necessary to use biocontrols in decisions
  • May be based on:
    • Statistical correlations from field observations
    • Numerous types of controlled experimentations
  • Requires that NE’s be monitored along with pest (cf. spider mite examples cited earlier)

• Read Chapter 11, Pesticides, by

March 22.

• EXAM on Friday, March 12