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Calculation of Environmental Thresholds (ETs) for Pest Management, Exercises of Pest Management

The LNM Institute of Information TechnologyPest Management

Methods for calculating environmental thresholds (ets) for pest management, including the most common heuristic method and more formal methods. Ets are used to prevent exceedance of injury levels (eils) and are one type of action threshold. The document also covers advantages and limitations of thresholds, and topics such as field history, monitoring climate, use of computer models, and cultural tactics. Cultural controls are preventative tactics that make crops less suitable to pests and more suitable to biocontrols, and have benefits and disadvantages.

Typology: Exercises

2012/2013

Uploaded on 08/31/2013

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How are ETs calculated?
• Most common method is heuristic. Most common rule of
thumb is 1/3 EIL.
• Two examples of more formal methods are:
• ET = EIL/r
(2) ET = EIL/(expected rate of change in pest population)
General notes on ETs
• ETs are the predictive part of an EIL/ET pair – one acts on an
ET in order to prevent the EIL from being exceeded.
• ETs are one type of “Action Threshold”. Other types were in
Pedigo & your text (pp. 201 – 202).
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Partial preview of the text

Download Calculation of Environmental Thresholds (ETs) for Pest Management and more Exercises Pest Management in PDF only on Docsity!

How are ETs calculated?

  • Most common method is heuristic. Most common rule of

thumb is 1/3 EIL.

  • Two examples of more formal methods are:
    • ET = EIL/ r

(2) ET = EIL/(expected rate of change in pest population)

General notes on ETs

  • ETs are the predictive part of an EIL/ET pair – one acts on an

ET in order to prevent the EIL from being exceeded.

  • ETs are one type of “Action Threshold”. Other types were in

Pedigo & your text (pp. 201 – 202).

  • Note your text’s discussion of limitations of thresholds.

Advantages of Thresholds

  • Conceptually easy to understand makes them easy to implement/adopt. Can also be represented in many formats: single numbers, tables, charts.
  • Scientific basis to threshold criteria
  • Flexibility gives broad applicability
    • Can be applied to a variety of pests in many situations
    • Can utilize many variables as the action variable. Climatic variables often used for pathogens.
    • Have been extended to take into account many other issues. Examples include
      • Age distribution
      • Multiple controls (e.g. biocontrol)
      • Environmental Impacts (i.e. macroeconomic “C” values)
      • Risk

Closely read the remainder of this chapter

  • Host Plant Resistance (Chapter 17)
  • Behavioral Control (Chapter 14)
  • Physical & Mechanical Tactics (Chapter 15)
  • Legislative Prevention (Chapter 10)

Cultural Management of Pests

  • Change the way the crop is grown so as to
    • Make crop less suitable to pests
    • Make crop more suitable to biocontrols
    • Make crop better withstand pest attack
  • All are preventative tactics, most target pest complexes.
  • Many individual types of tactics, each of which has a narrow

application range.

  • Read Introduction on p 413 - 414

Basic Categories/Examples of Cultural Techniques

  • Prevention/Preplant
    • Ex: use weed-free seed
  • Field Preparation & Planting
    • Ex: increase planting to reduce disease
  • Cropping Tactics
    • Ex: use barrier crops to help exclude insects
  • Harvest Tactics
    • Ex: harvest early to reduce yield loss
  • Sanitation
    • Ex: pick up prunings to reduce pathogen inoculum
  • Fast acting
  • As a group, relatively sustainable

Disadvantages of Cultural Controls

  • Some are not environmentally benign (e.g. conventional tillage,

residue burning)

  • May alter crop value or gross income (planting date, harvesting,

spacing)

  • Some are labor/energy intensive (pruning, tillage)
  • Widespread adoption may be low
  • Many conflicts

Conflict Illustration

Conflict Illustration

Conflicts Occur with:

  • Agronomic Traits
  • Other Pests
  • Markets
  • Other Cropping Practices

Prevention/Preplanting Tactics

  • Site selection
  • Preventing pest transport (equipment, soil)
  • Use pest-free seed/transplants/rootstock
  • Intercropping – Two or more useful crops
  • Cultivar mixtures – Different cultivars may have to be planted in

different fields to create a “cultivar patchwork”. Multilines will

be discussed in HPR.

  • Water Management

Cropping Tactics – Crop Rotation

  • Intercropping in time
  • Especially effective against soil-based pests: Weeds, soil-borne

pathogens, root-feeding insects

  • For weeds:
    • Changes weed complex
  • Not stand alone weed mgmt, instead used to facilitate weed mgmt

Harvest Tactics

  • Harvest timing (early vs late) -- may use early/late varieties, dessicants, defoliants, or other growth regulators. - Crop matures before pests build up - Harvesting operation itself causes extensive mortality.
  • Harvest method
  • Partial Harvesting -- Prevents movement to high value crops
    • Maintains young age structure
    • Concentrates natural enemies (usually more mobile)