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 decision

a. No action

Damage caused by pest doesn’t warrant action

b. 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