Modelling the Transport and Biological Effect of Pesticide

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Modelling the Transport and Biological Effect of
Pesticide

• Stephen J. Cox

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Aims of crop spraying models

• Saving money
• Improving biological control
• Reducing environmental contamination

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Processes involved in spraying
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Spray production

• Formulation
• density, viscosity, surface tension
• Droplet size distribution
• log normal - 2 parameters
• Initial velocities
• angles normally distributed from a hydraulic fan
  nozzle

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Transport equations

• Ballistic
• Random
• Combined

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Trajectories of 10 droplets
100 mm 300 mm
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Model barley plants
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Capture

• Interception
• simple collision in space
• impaction efficiency correction for local
  airflow deviations
• Rebound

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The deposit on individual plants
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Deposit pattern for 104 droplets (log scale)
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Possible improvement

• Entrained air and tractor wake
• Waving crop
• Better rebound model
• Speed of calculation

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Killing caterpillars

• Distribution of pesticide on leaf
• Markov chain model of insect behaviour dependent
  upon degree of poisoning
• Simple pharmacokinetics

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Number still alive versus time
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Factors affecting proportion dead
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Simplest model of a leaf
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Concentration profile after1 Minute
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Concentration profile after6 Minutes
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Concentration profile after1 Hour
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Further work

• More layers in model - perhaps include both sides
  of leaf
• Comparison with experimental data
• Integrate with a model of fungal growth to allow
  efficacy to be investigated