Pest Management Decisions
Feb 24, 2016
Pest Management Decisions
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
Major steps in the decision-making process
1. Pest Identification Pest species must be correctly identified Tells us about biology, life cycle, control strategies, etc.
2. Population Determination Monitoring to determine pest population size, pest distribution, stage of
development, presence and distribution of beneficials
3. Damage and Economic Loss Evaluate potential damage to crop relative to pest density Consider action, economic and/or damage thresholds
Major steps in the decision-making process
4. Available Control Tactics Review what tactics are available and their efficacy Cost of implementing control vs. economic returns expected
Current and projected market value
5. Interactions Consider interactions among target pest and other pests and beneficials in the
system
6. Environmental and legal constraints Consider local, regional environmental and societal regulatory restrictions
Major steps in the decision-making process
7. Make a decisiona. No action
Damage caused by pest doesn’t warrant actionb. Reduce crop susceptibility to damage
Change some aspect of the system to limit damage to an acceptable level
c. Reduce pest population size Recommended action that will reduce pest population
d. Combination of b. and c.
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
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
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
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
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
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
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
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
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
Assignment
Choose two weeds, two insects and two diseases. List which technique is used to monitor each.
Economic Thresholds
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
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
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
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
Examples of thresholds??
What are some of the thresholds written in our insect fact sheets?
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
Other factors that affect pest management
Cropping History Field Location and Size Weather Monitoring