Pest Control

1
Pest Control

• David Zilberman
• ARE 253 PP253

2
Pesticides Damage Control Agents

• Pests include
• Big animals (elephants, coyotes)
• Small creatures (mice, birds)
• Insects
• Viruses
• Weed
• Control types--Chemical
• Agronomic fences,hoes, tractors, traps
• Biological cats, dogs, predators of pests
• Seed varieties including genetically modified
  crops pest resistant, pesticides tolerant

3
Modeling Pest-Control Choices

• Y OUTPUT Z INPUT (fertilizer)
• Q g(Z) - potential output
• X pesticides-damage control agent
• d(N) fraction damaged, N final pest
  population
• N h(X, M) M initial pest population,
  pesticides reduce population from M to N
• Y g(Z)(1 - d(h(X))
• Firms aim to maximize profits
• P output price, W input price, V
  pest-control price
• A fixed application cost
• Profit Pg(Z)(1 - d(h(X,M)) - ZW - VX - A

4
Pest Population and Pest Control

• At optimal solution
• VMPZ P(?g/ ? Z) (1 - d(n(X,M)) W.
• Value of marginal product of input input
  price.
• VMPX -P g(Z)?d/?N ?n/?X V.
• Value of marginal product of pest control its
  price.
• Larger initial population requires more
  application.
• If initial population is sufficiently small and
  does not cover fixed application cost, do not
  apply.
• Application is warranted if a population
  threshold has exceeded. Apply only if M gt
  threshold.
• Estimation population is costly.

5
Preventive vs. Responsive Application

• Pest population arrival time and size are random.
• Preventive applications. Based on average
  performance may lead to overspraying. Standard
  spraying based on a large population will occur
  when pests do not arrive or population is small.
• Responsive application requires costly monitoring
  of population will save chemicals but require
  costly monitoring and may lead to slow or
  incomplete response to invasion.
• Integrated pest management. Relies on monitoring
  of pest population and combines a mixture of
  strategies that aim to minimize use of chemicals.

6
Effective Pest Management Biology

• Predator-prey consideration
• Suppose two pests cause damage, and N1 N2
  denote their populations.
• Pest 1 is the predator of 2 so
• N1 n1(X1, M1) N2 n2 (N1, M2)
• The optimal rule for applying pest control 1 -X1
  
  VMPX1 MCN2 V
• The value of pesticides in controlling pest 1
  marginal cost of larger population of pest 2
  pest control cost.
• Control of pests that are also predators of other
  pests should recognize their benefits and reduce
  application levels accordingly.

7
Resistance

• Occurs when efficacy of pesticides declines as
  use of chemical increases over time.
• Since pests move across farms, it is a common
  problem. Individual producers ignore future
  resistance cost associated with pesticides use.
• Policy intervention
• (Ideally) Incentives (tax or subsidy) to reflect
  the social cost of resistance.
• Use regulation to limit the use of materials to
  worthwhile situations.
• Research to identify alternatives.

8
One Persons Pest Is Another Persons Game

• The definition of pests is relative
• Elephants damage farms but can be a source of
  eco-tourism income.
• Feral pigs cause damage to field crops, but many
  will pay to hunt them.
• Pest management strategies should take advantage
  of strategies that will take advantage of pests
  and reduce the cost of pest control.
• The beneficiaries of green pest control methods
  should pay to support them.

9
Health Risks of Pesticides

• Food safetymortality or morbidity resulting from
  chemical residuesinclude
• Acute impactspoisoning, allergic responses.
  Poisoning when packaging materials used for food
  consumption
• Chronic impactscancer.
• Much uncertainty about the food safety effect.
• Worker safetydamage to mixer applicator and
  farmers may be high, especially if caution is not
  taken.
• Environmental safety
• Damages to fish, birds, beneficial insects.
• Some pesticides are possible or definite
  endocrine disrupters (block the action of male
  hormones).

10
Controlling Pesticide Externalities

• Registration requirements. Before a product is
  introduced, it must pass a battery of test to
  identify obviously risky products (carcinogens).
• Incentives. Taxes and subsidies to pay for
  damages.
• Limits on total use. Tradable permits to users.
• Ban. Complete or partial bans on chemicals?.
• Restrictions on applications. Limits on when,
  where, and how chemicals are applied (e.g., not
  near schools, when it is windy, or aerially
  spraying).
• Direct control. Protective clothing, food
  treatment requirements, and reentry regulation to
  sprayed fields.
• Education and information. Notification
  regarding spraying activities and possible
  exposure risks.

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Possible Pesticide Use Levels
MCMarginal Cost MBMarginal Benefit MECMarginal
Externality Cost MRCMarginal Resistance Cost
Social optimumpoint A Monopoly Price C Quantity
B Competitive outcomepoint E
Price
Demand MB of production
Monopoly Price
C
Marginal revenue
MC MRCMEC
A
MC
E
Quantity
B
12
Possible Use Levels of Pesticides

• If a manufacturer is a monopoly (has a patent),
  there may be under-use of pesticides if a
  monopoly price hike is greater than marginal
  externality and resistance costs.
• Social optimum occurs if marginal benefits of
  pesticides in production equals sum of marginal
  externality, resistance, and production cost.
• Without intervention, the most use occurs where
  marginal benefits equal marginal cost of
  production.

13
Pesticides in Developing Countries

• Under-application in some situations.
• Many developing countries are in the humid tropic
  with major pest problems, but not many have pest
  control tools, since most pesticides have been
  developed for problems in developed countries and
  temperate zones.
• Adaptation of pest control solutions is costly,
  and ability to pay for companies investment are
  limited.
• Pesticide application equipment is costly, and
  peasants frequently face credit constraints.
• Techniques such as bio-control (mealybug in
  cassava) and GMOs are especially useful (and easy
  to apply and spread).
• Safety rules may not be followed, and there are
  cases of overappliation.

14
Reasons for overappliction

• There is lack of enforcement of environmental
  regulation, resulting in overuse and exposure.
• Pesticide patents may not be registered or
  recognized, and cheap old generic ones are used.
• Pesticides may be subsidized in some countries
  (China).
• Cheap materials may be combined with cheap
  application equipment, and unregulated setup will
  lead to environmental dangers.

15
The Good and Bad Sides of Pesticide Use

• Average pest losses in Indian cotton are 50-60.
  Insect pests losses In the United States and
  China are 12 15, respectively. Its climate
  less pesticides.
• Yield-increasing pesticides may prevent
  deforestation and acreage of farming.
• The low productivity effect of pesticides in rice
  in the Philippines and Indonesia, combined with
  worker safety effects, suggests much overuse
  there.
• Banning chemicals in most cases is suboptimal.
  The problem is not chemicals but how they are
  being used.

16
From Chemicals to GMO

• Pesticide regulations have triggered introduction
  of new chemicals and GMOs.
• Bt cotton has reduced pesticide applications in
  US and china by 50-60,but yield effects are
  between 0-5. In India yield effects are 50.
• The high pest pressure in developed countries and
  lack of pesticides suggest high yield-increasing
  potential for GMOs.
• Effort in adaptation and development of
  appropriate genetic materials and access to
  Intellectual Property Rights are needed.
• Possible externalities need to be inspected.

17
Expected Yield Effects of Pest-Resistant GM Crops
in Different Regions
18
A General Problem Policies to Control
Environmental Risks

• The impacts of policies are uncertain, and the
  environment is subject to stochastic forces.
• Methodologies to both model risk and analyze
  choices under risk are crucial for effective
  policymaking.
• There are alternative approaches to risk.
  Economic and decision theoretic models measure
  risk as deviations from the norm or average.
  They emphasize assessing the impact of such
  deviations on behavior and their cost.
• Public health develops risk assessment techniques
  that define risk explicitly as the probability of
  data outcome.

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Properties of Risk Assessment Models

• Risk probability that a member of a population
  will die or get sick during a period of time.
• Risk-generating functions relationship between
  risk and processes that cause it.
• The knowledge needed for risk-generation
  functions is interdisciplinary. It provides the
  base for both estimation and policymaking.
• Risk assessment models can be used to assess
• Human health risk
• Environmental health risk (risk to fish)
• Food security

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Chemical Application Risk
Pollution control policies
Barriers/filters
Protective clothing
Medical treatment
Risk
Contamination
Exposure
Dose/ Response
Transfer fate




Risk of chemical residues can be reduced
by Reducing application levels through taxes,
direct control,etc. Blocking movement of residue
to and in bodies of water (can be induced by
incentives). Reducing human exposure by
filters,protective clothing. Treatment in case
of poisoning and injury.
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Farm Worker Pesticides Risk

• Let r represent individual health risk where
• r f1(X,B1) f2(B2) f3(B3)
• initial exposure exposure dose/response
• X pollution on site (i.e., the level of
  pesticide use)
• B1 damage control activity at the site (i.e.,
  protective clothing re-entry rules)
• B2 averting behavior of individuals (i.e.,
  washing fruits and vegetables)
• B3 the medical control of pollution dosage.

22
Modeling Environmental Risk

• The modeling principles used to model human
  health risk from pesticides also apply to
  modeling risk to, say, birds.
• There are processes of contamination transfer and
  fate exposure and dose response (transfer and
  fate and contamination are most important in this
  context).
• These processes are controlled through policies.

23
Policy Optimization under Risk

• A reasonable policymaking principle-
• The objective is to maximize economic welfare
  subject to the constraint
• Probability (Risk lt R) gt ?
• R target level of risk
• ?. safety level (measures the degree of
  social risk aversion)
• ? might represent the degree of confidence we
  have in our risk estimate.
• For example, policymakers may aim to maximize
  economic surplus given that risk from pesticides
  cannot exceed 1 million with a 95 probability.

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Uncertainty and Assessment

• Use of higher degree of statistical reliability,
  ????? leads to higher risk estimate. The risk of
  a chemical may not increase .05 with ???.95,
  but may exceed it with ???.995 .
• Is useful to use consistent reliability
  requirements for all risk estimates to allow
  comparisons.
• It may be useful to identify a target group in
  the population (say, top 95 in terms of
  vulnerability) and compare how policies affect
  risk to this group.

25
Sources of Variability

• Coefficients of risk-generation functions vary.
• We may not have a reliable number representing
  coefficients of specific processes.
• The risk function may be r a? b? g X and the
  coefficients may be stochastic.
• The causes of variability
• Heterogeneity can be handled by more specific
  analysis.
• Randomness.
• Uncertainty (lack of knowledge) can be reduced by
  learning.

26
Pesticide Registration

• Main form of policy is pretesting and
  registration.
• Objective is to eliminate risky pesticides and
  minimize side effects.
• Once a product is discovered to be problematic,
  it may be banned or its use restricted.
• Intensive testing is beneficial to corporations
  because it increases entry costs (50 million to
  introduce a new chemical) and assures their
  market power.
• It reduces availability of new products and
  results in orphan diseases, especially used in
  specialty crops and developing countries.
• Governments and donors may need to subsidize
  introduction of new products beneficial to
  society but not to private sectors.

27
Pesticide Doctors

• Productivity of pesticides can be enhanced, and
  their environmental impact reduced if their
  performance is monitored and decisions on what
  and when to apply are optimized.
• One approach is to restrict diagnosis of
  pesticides to certified pesticide consultants and
  applications to certified applicators.
• Extension can train both types of professionals.
  They can also be required to document pesticide
  applications and may be liable for wrong choices.
  
• Optimal sharing of liability for mistakes is a
  challenge, but if done correctly can improve
  policy.