Pest Management Decisions

1. Pest Management Decisions

2. IPM decision staircase • Some basic information is essential • Information must be obtained from bottom to top • Missing information will lead to incorrect decisions • Each step interacts with the other in some way

3. Major steps in the decision-making process • Pest Identification • Pest species must be correctly identified • Tells us about biology, life cycle, control strategies, etc. • Population Determination • Monitoring to determine pest population size, pest distribution, stage of development, presence and distribution of beneficials • Damage and Economic Loss • Evaluate potential damage to crop relative to pest density • Consider action, economic and/or damage thresholds

4. Major steps in the decision-making process • Available Control Tactics • Review what tactics are available and their efficacy • Cost of implementing control vs. economic returns expected • Current and projected market value • Interactions • Consider interactions among target pest and other pests and beneficials in the system • Environmental and legal constraints • Consider local, regional environmental and societal regulatory restrictions

5. Major steps in the decision-making process • Make a decision • No action • Damage caused by pest doesn’t warrant action • Reduce crop susceptibility to damage • Change some aspect of the system to limit damage to an acceptable level • Reduce pest population size • Recommended action that will reduce pest population • Combination of b. and c.

6. Monitoring • Process by which number and life stage of pests present in a location are established (aka scouting) • Key objectives are to determine: • Pest stages present in the crop • Phenology of pest • Growth stages through which the pest passes in relation to time • Density of pests in the crop • Number of pests per unit area • 2,000 seeds/m2 • Number of pests per plant part • 5 aphids/plant • Number of pests per unit of sampling effort • 10 beetles per 5 sweeps of a sweep net

7. Steps in Monitoring • Record type of plant being monitored, its size, location, condition, and date and time inspection took place • Monitor the crops for insects (using methods described above) on a regular or weekly basis, and note number of pests, their stage of growth, and distribution • Identify any beneficial insects • Take representative plant samples in the field • Assess the growth status and general health of the crop • Record the findings on field data sheets

8. Techniques for Assessing Pest Populations • There is no single monitoring technique that works for all categories of pests • Overall considerations • Data required • Actual pest numbers, presence/absence, phenology • Time of day when samples are collected • Weather conditions • Windy, cool/hot, or rainy conditions can alter pest visibility • Soil conditions • Phenological development of organism • Weed seeds vs. seedlings, 1st vs 5th instar larvae differ in size • Pest location • Soil/plant host, in-crop/field edges

9. Common Monitoring Techniques • Direct Pest Observation/Counting • Quadrats • Organisms present within an area • Weeds • Plant Samples • Samples of plant parts • Egg and larval counts, estimating leaf/root damage

10. Common Monitoring Techniques • Direct Pest Observation/Counting • Knockdown • Pests are dislodged from host onto a collecting surface/container • Larvae and non-flying insects • Sweep Nets • Nets are strong, usually about 15 inches in diameter at opening • Insects only • http://www.youtube.com/watch?v=DGggRMwpnY8

11. Common Monitoring Techniques • Damage Evaluation • Sometimes looking at symptoms or injury is the only way to determine pest presence • Signs or symptoms • Pushed up soil • Frass • Slime trails • Spores, sclerotia, mycelium • Physical injury • Remote sensing

12. Common Monitoring Techniques • Trapping • Primarily used for insects • Can detect a presence but not usually reliable for population size • Will help monitor population activity and frequency of insect vectors • Visual • Sticky traps • Bait traps • Pitfall traps • Pheromone traps • Blacklight

13. Common Monitoring Techniques • Soil Sampling • Soil-borne pests • Can be time consuming, laborious • Shovels, scoops, cores • Water submersed, sieved • http://www.youtube.com/watch?v=9bMxSDSYp3E

14. What do we need to consider when we are taking samples in the field? • Field size • Economic value of the crop • Sample location • Pest density • Sample size • Sampling patterns • Goals of manager • Mobility of the pest • Timing of sampling • Frequency of sampling

15. Assignment • Choose two weeds, two insects and two diseases. • List which technique is used to monitor each.

16. Economic Thresholds

17. Damage Concept • Injury • The physical harm or destruction to a valued commodity caused by the presence or activities of a pest • consuming leaves, tunnelling in wood, feeding on blood, etc. • Damage • The monetary value lost to the commodity as a result of injury by the pest • spoilage, reduction in yield, loss of quality, etc. • Any level of pest infestation causes injury, but not all levels of injury cause damage

18. Just how much damage can we tolerate? • At some point, a pest begins to cause enough damage to justify the time and expense of control measures • But how does one know when this point is reached? • How much financial loss is the pest causing? • How much will it cost to control the pest? • Economic Injury Level • The pest density where economic value of the crop loss prevented by the control action is equal to the cost of that control action • Determined through extensive research

19. Economic Injury Level • P=C/(V x I x D x K) • P=Pest population expressed as a density (e.g., number of pests per plant) • Point where damage equals cost of control (EIL) • C=Management costs (i.e., costs of control) • V=Market value per unit of production • I=Injury per pest equivalent • D=Damage per unit injury • K=Proportion of damage that must be tolerated

20. Economic Threshold • Threshold • Stimulus has reached a sufficient level to provoke a response • Must be qualified further • Economic Threshold • Pest density at which control action must be taken to prevent the population from increasing to the EIL • ET occurs at a lower population that the EIL…why? • In weed science, the ET is equal to the EIL

21. Examples of thresholds?? • What are some of the thresholds written in our insect fact sheets?

22. Limitations of Thresholds • Environmental conditions can alter thresholds • Some pathogen populations are impossible to count accurately • There may not be any available controls for a pest once it reaches a detectable stage • Some pests cannot be cured • Multiple pests may attack a given crop • Not enough data available to establish the thresholds

23. Other factors that affect pest management • Cropping History • Field Location and Size • Weather Monitoring