How are economic thresholds established?. Pest Management Strategies Eradication – this is a strategy in which extensive efforts and costs are provided.

How are economic thresholds established?

Pest Management Strategies

• Eradication – this is a strategy in which extensive efforts and costs are provided in the short term to completely remove the pest and therefore provide unhindered produce development in future periods;

• Prophylaxis – this is a strategy of insurance, in which pest controls are applied systematically, periodically and generally preventively regardless of the pest population;

• Containment – the intention is to ensure the pest population stays below a specific level. The producer in this situation accepts some loss of yield (and therefore revenue) and controls the pest when it is cost-effective to do so.

Cousens (1987)

History of Pest Management

• Synthetic Pesticide Era--1939 to ?????Prior to this time, insecticides were formulated from petroleum, coal tar distillates, plants or inorganic compounds

1930'strend toward synthesizing new compounds

DDT- synthesized by a German graduate student 1873- Paul Muller, (Swiss) discovers insecticidal activity- saves many soldiers' lives during WWII (body lice - typhus)- such an impact on human health -- Muller wins 1948 Nobel prize in medicine

More soldiers were lost in WWII due to mosquito-borne disease than in battle.

• During WWII both the Germans and the Allies working on the development of organophosphates as nerve gases. They discover the insecticidal properties of these chemicals

• After WWII development of other chlorinated hydrocarbons and organophosphates as pesticides

• 1950's early 60's• "The Green Revolution"

- synthetic pesticides and fertilizers the answer to world hunger!! - trend away from understanding pest phenology, density or damage potential and toward pure chemical approach

• 1962• Silent Spring

- Adverse effects on wildlife, water quality, human health?- DDT found in milk and foods (biomagnification)- Resistance of pests to pesticides Response to book leads eventually to public policy changes in 1970's

• 1970'sUSDA creates nationwide IPM Program in Land Grant UniversitiesEPA created & given jurisdiction over pesticide registration & regulation

• 1980'sIncrease in IPM research

IPM concept (1972)

• Integrated control.

• Pest management and Economic injury level.

• Environmental protection

Development of the concept

Pierce, W. D. 1934:

At what point does insect attack become damage?

Who came up with the damn idea?

• Emphasized concerns regarding excessive and inappropriate uses of insecticides (4 R’s)

- Resistance- Resurgence- Residue- Risk to human health & environment

Integrated control—the conceptual foundation of all modern days IPM programs

Sophisticated idea of pest control predicted on the complementary action of chemical and biological control

4 basic elements:- Threshold for determining the need for control- Sampling to determine critical densities- Understanding and conserving bio-control capacity of system- Use of selective insecticides when needed

General Equilibrium Position

GEP

Time

Popu

lati

on d

ensi

ty

0

GEP

EIL

Time

Popu

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ensi

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0

GEP

ET

EIL

Time

Popu

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0

Injury & Damage

Damage: Measurable loss of host utility (quantity/quality/aesthetics).

Injury: The effect of pest (insect) activities on host physiology that is usually deleterious.

Certain level of injury may not produce damage or yield loss

Damage boundary: The level of injury (number of insects) at which damage occurs

Pierce, W. D. 1934:

At what point does insect attack become damage?

EIL & ET

• EIL= C/VIDK

EIL= number of injury equivalents per production unit (e.g. insects/ha)

C= cost of management activity ($/ha)

V= market value ($/kg)

I= injury units per insect per production unit (e.g. proportion defoliation/(insect/ha)

D= damage per unit injury (e.g. kg reduction/ha)

K= proportionate reduction of the insect population

Pedigo et al. 1986

O 1 2 4 O 1 2 4 O 1 2 4Range of pest densities

Experiment without management action

Calculate yield and revenue

O 1 2 4 O 1 2 4 O 1 2 4Range of pest densities

Experiment with management action

Calculate yield and net revenue

O 1 2 4O 1 2 4

Experiment without management action

Experiment with management action

Yield

Manag. cost

Net returns

8

0

80

10

20

80

10

0

100

11

20

90

6

60

9

20

70

Total returns 100 80 60 110 100 90

ET

EIL

Time

Popu

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ty no losses

benefit > cost

cost > benefit

economic losses

Factors affecting EIL

ET categories

• The economic threshold is simply the operational criteria for administering pest control action (Higley and Pedigo, 1996)

• Simple threshold: ET is usually arbitrarily set to some reasonable level below the EIL to allow sufficient time for making the treatment decision and scheduling control activity

• Comprehensive threshold

How to express ETs?

1) % damage to leaves, plants, foliage, or2) # of plants showing damage; or # adults or larvae/stem / plant.

3) # adult insects or larvae / m2

4) # adult insects or larvae/sweep

Examples of ETThrips

Barley, Oats7 - 8 thrips/stem prior to head emergence

Red Clover50 - 80 thrips per flower head

Beet Webworm Canola 20 - 30 larvae/m2

Clover cutworm Canola, Mustard, Flax 20 - 30 larvae/m2

Cutworms

Cereals 3 - 4 larvae/m2

Oilseeds25 to 30 per cent stand reduction

 Pea2-3 larvae /m2 in the top 7 cm (3 in.) of soil 

Diamondback moth Canola, Mustard

100 - 150 larvae/m2 in immature and flowering fields

200 - 300 larvae/m2 in podded canola fields

Classification of pests on the basis of ET

Non-economic pest

Occasional pest

Perennial pest

Severe pest

Direct & Indirect Pests

Comparison of Direct and Indirect Pests

Characteristic Direct IndirectCommodity Marketable Non-Marketable

Yield-Pest Relationship Simple Complex

Pest Status Usually Key Pest Any

Pest Group Insects & Pathogens Any

Farmer Tolerance Low Higher

Limitations of EIL/ET

• Limited applications for medical pests, veterinary pests, & pathogens

• Market value of human health and life?• Variable market values• Substantial background research to calculate injury per insect

and injury/plant response relationship• Multiple pests?• Environmental cost?

Present and future prospect

• Provides practical approach to pest related decision making

• EILs for guilds of species with similar injuries i.e. single EIL for complex of species

Two Basic Decision Categories in IPM

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

Strategy vs. Program (Strategic Plan)

Implement Tillage Tactic

ConserveBiologicalControls

ApplyInsecticide 2if neccessary

Implement Tillage Tactic

ConserveBiologicalControls

Too ManyCaterpillars?

ApplyInsecticide 2

Weekly CountInsect A

Caterpillars

No

Yes

Strategy Pest Management Program

• 1990'sNew genetically engineered Bt crops (corn, potatoes) come into useHow will these fit into IPM programs?

• 2000 and beyond??Pest management is always changing and we cannot predict the future.