Pest ControlPesticides: Damage Control AgentsModeling Pest-Control ChoicesPest Population and Pest ControlPreventive vs. Responsive ApplicationEffective Pest Management & BiologyResistanceOne Person’s Pest Is Another Person’s GameHealth Risks of PesticidesControlling Pesticide ExternalitiesPossible Pesticide Use LevelsPossible Use Levels of PesticidesPesticides in Developing CountriesReasons for overapplictionThe Good and Bad Sides of Pesticide UseFrom Chemicals to GMOExpected Yield Effects of Pest-Resistant GM Crops in Different RegionsA General Problem: Policies to Control Environmental RisksProperties of Risk Assessment ModelsChemical Application RiskFarm Worker Pesticides RiskModeling Environmental RiskPolicy Optimization under RiskUncertainty and AssessmentSources of VariabilityPesticide RegistrationPesticide “Doctors”01/14/19 Pest ControlDavid ZilbermanARE 253 PP25301/14/19 Pesticides: Damage Control AgentsPests include:Big animals (elephants, coyotes)Small creatures (mice, birds)InsectsVirusesWeedControl types--ChemicalAgronomic: fences,hoes, tractors, trapsBiological: cats, dogs, predators of pestsSeed varieties including genetically modified crops: pest resistant, pesticides tolerant01/14/19 Modeling Pest-Control ChoicesY = OUTPUT Z = INPUT (fertilizer)Q = g(Z) - potential outputX = pesticides-damage control agentd(N) = fraction damaged, N = final pest populationN = h(X, M) M = initial pest population, pesticides reduce population from M to NY = g(Z)*(1 - d(h(X))Firms aim to maximize profitsP = output price, W = input price, V = pest-control priceA = fixed application costProfit = Pg(Z)*(1 - d(h(X,M)) - Z*W - V*X - A01/14/19 Pest Population and Pest ControlAt optimal solutionVMPZ = 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 > threshold. Estimation population is costly.01/14/19 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.01/14/19 Effective Pest Management & BiologyPredator-prey considerationSuppose two pests cause damage, and N1 & N2 denote their populations. Pest 1 is the predator of 2 soN1 = n1(X1, M1) & N2 = n2 (N1, M2)The optimal rule for applying pest control 1 -X1 VMPX1= MCN2 + VThe 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.01/14/19 ResistanceOccurs 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.01/14/19 One Person’s Pest Is Another Person’s GameThe 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.01/14/19 Health Risks of PesticidesFood safety—mortality or morbidity resulting from chemical residues—include:Acute impacts—poisoning, allergic responses. Poisoning when packaging materials used for food consumptionChronic impacts—cancer.Much uncertainty about the food safety effect. Worker safety—damage 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).01/14/19 Controlling Pesticide ExternalitiesRegistration 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.01/14/19 Possible Pesticide Use LevelsABMC +MRC+MECMCDemand MB of productionMarginal revenueMonopoly PriceCSocial optimum=point AMonopoly =Price C Quantity BCompetitive outcome=point EEQuantityMC=Marginal CostMB=Marginal BenefitMEC=Marginal Externality CostMRC=Marginal Resistance CostPrice01/14/19 Possible Use Levels of PesticidesIf 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.01/14/19 Pesticides in Developing CountriesUnder-application in some
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