Pest Management Tactics & Strategies

• Covers chapters 8 – 17 in text• Includes all major tactics categories:

– Biological control– Cultural control– Pesticides– Mechanical/Physical controls– Behavioral-based control methods– Regulatory-based concepts

• Also includes all factors necessary for choosing/deciding among controls– Monitoring methods– Decision tools

Pest Management Decision Categories

• Tactical vs Strategic• Preventative vs. Curative• In-Season vs. Intra-Season• Control vs. Non-control (i.e. monitoring)• Single Dimension vs. multidimensional

– Temporal: Single Period vs. Multiperiod– Biological: Single spp. (pest) vs. Multiple spp. (pests,

beneficials, other non-targets)– Economic: Immediate payback vs. multiple economic

considerations.

Who makes IPM Decisions?

• Growers who manage the pests?• Consultants who make recommendations to

growers?• Extension specialists who develop

educational/training materials?• Researchers who decide which topics to

research?• Administrators who decide which things to fund?• Others?

Pest Management Strategic Plans

• Driven by national programs• Closely associated with Crop Profiles and

Crop Timelines• Provide a framework for IPM decisions• No specific format, but most include:

– Pest profiles for each important pest– Management tactics currently used– Additional needs in research, extension,

training

Decisions about how IPM needs to advance in a particular cropping system. A planning tool.

Assignment

• Split into groups of 3• Each group finds a Pest Management Strategic

Plan• Distribute the web site for the plan over IPM-L by

Thursday, Feb. 19.• Each group discusses their plan in class on

Wed., Feb. 25• Suggestion: One person discusses the pests,

one discusses the tactics, one discusses the needs.

Most Decisions are Tactical & Follow a Procedure

1. Identify pest2. Determine pest population density3. Evaluate potential damage4. Review available control tactics5. Consider possible interactions with other

pests6. Evaluate legal/environmental issues7. Make a decision

The Decision Itself

• Must rely on a priori objective criteria. Often an economic framework.

• Four possibilitiesA. No action

B. Reduce Pest Population

C. Reduce Crop Sensitivity to Damage

D. B & C above

8. Follow-up to confirm expected outcome

An Alternative View to Fig. 8-1

Identification: Focuses on early seasonality factors

• Pathogens – Identification of conditions leading to disease often more important than identifying the pathogen itself.

• Weeds – Seedling identification is the main issue

• Arthropods – Knowing when immatures will be present often a key to identification of pest problems.

Monitoring

• Synonymous with “Scouting”, “Sampling”, “Pest Surveillance”

• Normally conducted to gather information needed by a decision tool

• Types of decision tools that using monitoring info include tools that:– Time preventative treatments– Determine whether curative controls are needed– Determine whether either of the above were effective– Select specific measures from several choices

Monitoring Determines:

• Crop Status (development stage, stand density, standing crop, etc.).

• Identity of pests• Phenology• Age distribution• Number or size of population

– Absolute (#/unit habitat or area)– Relative (#/unit effort)– Qualitative (Scaled from “low” to “high”)

Requirements of Monitoring Methods

• Simple to use

• Fast

• Inexpensive

• Applicable to a broad range of pests

• Reliable for decision making purposes

Decision-making reliability is crucial

• Credibility of IPM depends on decisions being correct

• Decisions have to be made with imperfect information & much of the imperfection is in monitoring data

• Every decision has a risk of being wrong• Lesson: We must understand how frequently our

decisions are incorrect and if there is a bias for overcontrol or undercontrol in our mistakes.

Reliability for Decision Tools

III

III IV

Pest Population on One Sample Date

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Max Tolerable Pest Pop.

Max Tolerable Pest Pop.

Consider this situation

Maximum Tolerable Level

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Say we sample at weekly intervals

Maximum Tolerable Level

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You have to make decisions at each

sampling date

Maximum Tolerable Level

I Correct decision to control

II Incorrect decision to do nothing

III Correct decision to do nothing

IV Incorrect decision to control

Time (Weeks)

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III

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I

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Construction of the decision diagram from sampling data

III

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Pest Population on One Sample Date

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Max Tolerable Pest Pop.

Max Tolerable Pest Pop.

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IIIIII

II

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XY

Example: Find 15 pest individuals at first sample, 20 on the second sample

III

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Pest Population on One Sample Date

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Max Tolerable Pest Pop.

Max Tolerable Pest Pop.

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IIIIII

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1520

15

20

Example: Then, on the third week, we find 40 pest individuals

III

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Pest Population on One Sample Date

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Max Tolerable Pest Pop.

Max Tolerable Pest Pop.

Time (Weeks)

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IIIIII

II

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20

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40

40

Not all decision points are equally susceptible to error

Maximum Tolerable Level

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III

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Reliability for Decision Tools

III

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Pest Population on One Sample Date

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Max Tolerable Pest Pop.

Max Tolerable Pest Pop.

Reliability Depends on Several Factors

• Specific species being monitored• Sites (site selection is important)• Specific technique being used• Number of samples taken

– Number at each site & number of sites• Weather• Observer (Scout) – Scout training is emphasized• Other minor effects:

– Field size, location, & aspect– Time of day (pests with diurnal activity)– Field history

Some of These are Linked

• Specific species being monitored• Sites (site selection is important)• Specific technique being used• Number of samples taken

– Number at each site & number of sites• Weather• Observer (Scout) – Scout training is emphasized• Other minor effects:

– Field size, location, & aspect– Time of day (pests with diurnal activity)– Field history

Reading for Friday

• Bring your blue books with you to class• Before class, look through them & be able to

locate the insect, weed, and pathogen monitoring sections of each book.

• Over the next few weeks (i.e. by the next exam), be able to (1) describe at least one monitoring method for each pest group in each cropping system, (2) compare two sampling methods from different crops, for the same pest group (e.g. insects) and in the same generic category (absolute, relative, qualitative).

Conclude Pest Monitoring

• Closely read the material on “Techniques for assessing pest populations”, pp. 183 – 197.– There will be an exam question here.– We won’t discuss it in lecture but may refer to

the material as if you are very familiar with it.– Be sure & apply this section to your analysis

in your term paper.

Decision Making

• Have discussed the “Maximum Tolerable Level” but have not defined it.

• Several Points to Make:– More than 1 “Level” is usually needed.– There are many kinds of such levels (cf. p. 200 – 201

in text for one list).– “Action Levels” or “Thresholds” are one general

method of decision making. We will discuss the other one (Optimization) later.

• The leader in this field has been L. Pedigo. Be sure & read his article in the “Reading Assignments”

The General Problem

Maximum Tolerable Level

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We actually see this:

Maximum Tolerable Level

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One problem is that we need to allow for management response time – The time between when a control decision

is made and when it takes effect

Maximum Tolerable Level

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Assume it takes 1 week to decide a control is needed, apply it, and for it to work

Decision must be made here

The other problem is uncertainty

Maximum Tolerable Level

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Solution to both problems (mgmt response time & uncertainty) is to create two levels

Maximum Tolerable Level

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Economic Threshold

Economic Injury Level

The maximum pest level that one is willing to tolerate.

The pest level at which action must be taken in order to avoid exceeding the EIL.

Quick Notes on EILs & ETs

• ET is always < EIL

• Units of ET & EIL are the same– Often pest density (absolute or relative)– Can also be injury (e.g. % defoliation)– Can also be implicit factors (e.g. leaf wetness)

• EIL & ET are hard numbers calculated from equations developed through field research.

The Basic EIL Model

The basic concept is that the EIL is the point at which the cost of a control = the value of damage that will be avoided by the control.

Value of damage avoided is a product of:Crop market value (V)Pest population density (P)Injury caused by each pest individual (I)Damage resulting from that injury (D)Proportion of total damage that cannot be avoided by

the control (K)

The Basic EIL Model

KDIV

CPEIL

'

CKDIPV '

Example

• Assume:– It costs $50/A to apply a given control (C)– A crop is worth $40/bushel (V)– Leaf area equal to two leaves/row foot are

eaten by each pest individual/plant (I)– The loss of two leaves/row foot results in the

loss of one bushel/A (D)– Even if you apply the control, you will still lose

10 % of the crop (K = 0.1, no units)

Example, Continued

KDIV

CPEIL

'

25.610.01240

50

EIL

Understanding the Units is Key

KDIV

CPEIL

'

25.610.02140

50

EIL

ft lv/rowbu/A

pest/plantft lv/row

bu$

$/A

EIL

Here’s how the units balance

ft lv/rowbu/A

pest/plantft lv/row

bu$

$/A

EIL

pest/plant

plant)1/1/(pest/

EIL Result:

EIL = 6.25 pests/plant

One of the principal advantages of EILs is their objectivity and scientific basis

KDIV

CPEIL

'

I, D, and K are determined empirically through field & laboratory experimentation.

C is, for the most part, easily determined.

For most agricultural crops, V is commonly available.

The principal source of subjectivity is in “Value”: Ex: Tree Crops & Gypsy Moth

KDIV

CPEIL

'

Time (Weeks)

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Resort Owner

Lumber Company

Municipality

Forest Ranger

Note that in all of these cases: C, I, D, & K are all the same. Only V changes.

Some examples of EILs & their derivation.

• EIL for Mexican Bean Beetle in Soybean – Details the development of an EIL.

• EILs for sorghum midge on sorghum – See Table 1 in the middle of the article.

• Common stalk borer in Nebraska corn

• Sweet potato whitefly on cantaloupe

How are ETs calculated?

• Most common method is heuristic. Most common rule of thumb is 1/3 EIL.

• Two examples of more formal methods are:

(1) ET = EIL/r

(2) ET = EIL/(expected rate of change in pest population)

General notes on ETs

• ETs are the predictive part of an EIL/ET pair – one acts on an ET in order to prevent the EIL from being exceeded.

• ETs are one type of “Action Threshold”. Other types were in Pedigo & your text (pp. 201 – 202).

• Note your text’s discussion of limitations of thresholds.

Advantages of Thresholds

• Conceptually easy to understand makes them easy to implement/adopt. Can also be represented in many formats: single numbers, tables, charts.

• Scientific basis to threshold criteria• Flexibility gives broad applicability

– Can be applied to a variety of pests in many situations– Can utilize many variables as the action variable. Climatic

variables often used for pathogens.– Have been extended to take into account many other issues.

Examples include• Age distribution• Multiple controls (e.g. biocontrol)• Environmental Impacts (i.e. macroeconomic “C” values)• Risk

Closely read the remainder of this chapter

• This is the only place where the following topics are discussed:– Use of field history– Field location & size– Monitoring climate– Use of computer/mathematical models– Aesthetic effects– Risk Assessment– Economics

Tactics

• Cultural Tactics (Chapter 16)• Biological Control (Chapter 13)• Pesticides (Chapter 11)• Resistance, Resurgence (Chapter 12)• Host Plant Resistance (Chapter 17)• Behavioral Control (Chapter 14)• Physical & Mechanical Tactics (Chapter 15)• Legislative Prevention (Chapter 10)

Cultural Management of Pests

• Change the way the crop is grown so as to– Make crop less suitable to pests– Make crop more suitable to biocontrols– Make crop better withstand pest attack

• All are preventative tactics, most target pest complexes.

• Many individual types of tactics, each of which has a narrow application range.

• Read Introduction on p 413 - 414

Basic Categories/Examples of Cultural Techniques

• Prevention/Preplant– Ex: use weed-free seed

• Field Preparation & Planting– Ex: increase plant spacing to reduce disease

• Cropping Tactics– Ex: use barrier crops to help exclude insects

• Harvest Tactics– Ex: harvest early to reduce yield loss

• Sanitation– Ex: pick up prunings to reduce pathogen inoculum

Good situations for cultural controls – Any of these will lead to the use of cultural controls

• Multiple simultaneous pests susceptible to 1 control method

• Crop has broad flexibility with respect to specific tactic but pest(s) does not

• Pest complex:– Has one or more key pests vulnerable to

environmental manipulation– Lacks pests capable of causing severe damage at low

density– Contains one or more pests that lack better control

alternatives

Benefits of cultural controls

• Often easily incorporated into the production system

• Predictable level of control, even if partial

• Fast acting

• As a group, relatively sustainable

Disadvantages of Cultural Controls

• Some are not environmentally benign (e.g. conventional tillage, residue burning)

• May alter crop value or gross income (planting date, harvesting, spacing)

• Some are labor/energy intensive (pruning, tillage)

• Widespread adoption may be low

• Many conflicts

Conflict Illustration

Time

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Crop’s Maximum Susceptibility Period

Normal Planting DateLate Planting Date

Conflict Illustration

Time

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Crop’s Maximum Susceptibility Period

Normal Planting DateLate Planting Date

Pest APest B

Often better to think of cultural control tactics as altering the pest complex rather than controlling it.

Conflicts Occur with:

• Agronomic Traits

• Other Pests

• Markets

• Other Cropping Practices

Begin Discussion of Cultural Control Categories

Basic Categories/Examples of Cultural Techniques

• Prevention/Preplant– Ex: use weed-free seed

• Field Preparation & Planting– Ex: increase plant spacing to reduce disease

• Cropping Tactics– Ex: use barrier crops to help exclude insects

• Harvest Tactics– Ex: harvest early to reduce yield loss

• Sanitation– Ex: pick up prunings to reduce pathogen inoculum

Prevention/Preplanting Tactics

• Site selection

• Preventing pest transport (equipment, soil)

• Use pest-free seed/transplants/rootstock

Field Preparation & Planting

• Cultivation & fertility• Plant & row spacing• Planting date (early vs late)• Planting method (depth, insertion method)• Mulches – organic & synthetic

Cropping Tactics

• Trap/Barrier Crops– Trap crops are destroyed with the pest– Barrier crops are on field perimeter

• Intercropping – Two or more useful crops• Cultivar mixtures – Different cultivars may

have to be planted in different fields to create a “cultivar patchwork”. Multilines will be discussed in HPR.

• Water Management

Cropping Tactics – Crop Rotation

• Intercropping in time

• Especially effective against soil-based pests: Weeds, soil-borne pathogens, root-feeding insects

• For weeds:– Changes weed complex– Not stand alone weed mgmt, instead used to

facilitate weed mgmt

Harvest Tactics

• Harvest timing (early vs late) -- may use early/late varieties, dessicants, defoliants, or other growth regulators.– Crop matures before pests build up– Harvesting operation itself causes extensive mortality.

• Harvest method• Partial Harvesting -- Prevents movement to high

value crops– Maintains young age structure– Concentrates natural enemies (usually more mobile)

Sanitation• Residue Removal• Burning/Flaming• Pruning (Removing Part of a Plant)

– Infected/Infested host tissue– Foliage that provides pest access– Alters canopy microclimate

• Roguing (Removing an Entire Plant)– Crop hosts– Alternate hosts

• Removing Other Resources (Often in Structures)– Harborage sites– Food/water sources

Biological Control

• One of the oldest pest management tools

• One of the most complex

• Excludes some biologically-based tools– Use of pests own behavior, biology, ecology– Use of crop resistance

• As a result, many definitions

Biological Control Defined

“The use of parasitoid, predator, pathogen, antagonist, or competitor population to suppress a pest population making it less abundant than it would be in the absence of the biocontrol agent

Emphasis on “population” helps exclude microbial pesticides

Biological Control

• Natural Control vs Biological Control– Natural Control is unmanaged, Biological

Control is managed. Definition of “managed” can be pretty loose.

• Natural Enemy = NE = “Biological Control Agent” & “Biocontrol Agent”– Any non-crop species that is antagonistic to

the pest. Includes predators, parasites, parasitoids, pathogens, competitors.

– May be managed or unmanaged.

Biocontrol Ideal

Time

EIL

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Biocontrol agent introduced

Pest

Biocontrol Agent

Three components interact to produce different biocontrol approaches

Cropping System

Pest Complex

Natural Enemy

Ideal

Emphasize the NE-Pest Interaction

NE lacks persistence, emphasize introduction

Emphasize effect of cropping system on NE

Cropping System Characteristics Conducive to Biocontrol

• Stability• Abiotic environment supports NE’s

– Temperature, moisture & shelter are all available as needed by NE

– Soils support soil-based NE’s

• Biotic environment supports NE’s– Alternative food sources available– Food for all life stages available

• Management practices compatible• Crop should have some damage tolerance

Biocontrol usually allows some injury and/or damage

EIL

Po

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Time

}

Biocontrol agent population always lags behind the pest population. This allows the pest population to build up to some extent.

ET = EIL/3

ET > EIL/3

Pest complex characteristics conducive to biocontrol

• Few species in the target niche

• Stable species composition

• Few key pests, few direct pests

• Ideally, minor pest species can act as alternate hosts/prey

Note the benefits of biocontrol, pp 338 - 339

Costs/Disadvantages of Biocontrol

• Usually requires change in management practice

• Increases scouting effort• Intrinsic time delay• Increased risk

– New NE’s may cause harm– Uncertainty about NE requirements/reliability– Always a potential for pest to escape control

• Fundamentally incompatible with other control tactics

Characteristics of Effective NE’s

• Can detect pest populations at low densities• Rapid population growth relative to pest

population• High pest destruction rate per capita• Synchronized phenology• Persistence at low host density• Persistence over cropping seasons/rotations• Tolerant of management actions• Willingly adopted by pest managers & growers

Common Trade-off Quesitons

• Generalists vs. specialists.

• Multiple vs. single biocontrol species

Generalists vs. Specialist NE’s

• Disadvantages of generalists:– Usually have lower numeric response– Kill fewer pests/unit time/NE– May be attracted to other species

• Advantages of generalists:– Better survival when pest population is low– More likely present at pest establishment– Multiple generalist species can co-exist as a

community (greater stability & reliability)

Phase Plane – Specialist NEP

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A specific phase plane’s characteristics are determined by (1) the biological parameters of the NE and Pest and (2) how closely the NE and Pest population dynamics are coupled. Specialists tend to be highly coupled.

Pest M

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Elementary Implications of the phase plane

Nat

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Ene

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Pop

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Pest PopulationMust be < EIL

Stable -- Good Too Many Pests, Two Few NE’s – Pests Have

Escaped Control

Too Few Natural Enemies -- Pest Resurgence Danger

NE Max

NE Min

Pes

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Too Many NE’s for Pest Pop. –NE Crash Imminent

Outcome Uncertain –Probably Bad

The “good” area often identified in decision guides as NE/pest ratios

Spider Mite Examples• Predator mite/pest mite (spider mite) on

apples must be at least 1:10 in Washington raspberries.

• In N. Carolina apples:– 1 Predator mite/18 pest mites– 25 Coccinellid predators/5 trees

• European red mite in W. Virginia orchards– If mites > ET, no spray if predator/mite > 2.5

Multiple vs. Single NE Introductions

• Denoth et al. 2002 analyzed 167 biocontrol introduction projects– Multiple introductions increased success for

weed control, decreased success for insects– In > half, a single NE species was ultimately

responsible for almost all realized biocontrol.– Recommend that multiple introductions should

be used with restraint when attacking insect pests