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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
lati
on d
ensi
ty
0
GEP
ET
EIL
Time
Popu
lati
on d
ensi
ty
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
lati
on d
ensi
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.