Principles of Pest Mgt. in the Urban Environment.

Principles of Pest Mgt. in the Urban Environment

Insect control in agriculture is a huge business: a 10 billion dollar business!

In agriculture, chemical control is still the most popular way to prevent and stop insect outbreaks and disease infections.

The mortality quotient: Mq = (Fecundity)(Sex Ratio)-1 (Fecundity)(Sex Ratio)

1. Fecundity = Female lays 100 eggs2. Sex Ratio = Females/Males + Females, e.g. collect 200 pupae and

rear them to adults & 100 males and 100 females; S.R. = 0.53. Mq = (100)(0.5) – 1

(100)(0.5)= 0.98

So: 100 – 98 = 2 (1 male & 1 female)

Control of the Gladiola Bulb Fly

In other words, to stop an outbreak of the gladiola bulb fly in a commercial operation you would have to kill 98% of the population.

Question: How do you know you have to control the bulb fly? How do you know you are about to have economic damage?

By killing 98.0% of the population:

Time

WS

BW

Ec

EcTh

By killing98.0% here,Pop. will level off.

The point is that’s it’s expensiveto establish and maintain gladiola bulbs – the bulbs are real valuable.

Should theydie

(1)The gladiola bulb fly is a direct pest -- feeds on the product you want to produce or sell

(2)This seems true, but how do youknow if it’s necessary to controlthe bulb fly?

(3) You better start sampling to see if you are about to cross the economicthreshold.

Production costs of gladiola bulbsat the Skagit Valley Bulb Farm.

• Equip. depreciation = 3.20/ac• Field labor = 14.00• Cultural operations -cultivation - planting - weeding - fertilizing - irrigation - etc. = 220.00

Bulb fly control = 80.00/ac

Harvesting & Packaging = 32.00Marketing = 10.00

Eq. Depr. $ 3.20 per acreField Labor 14.00 “Cult. Oper. 220.00 “Bulb Fly Prot. 80.00 “Harvesting etc. 32.00 “Marketing 10.00 “

Total Costs $359.20 per acre

I. Expected Production = 850.00 bushels/ac.II. To make costs; sell at $ 0.423/bu. i.e. (0.423)(850) = $ 359.20III. To make 100% profit you sell at = $ 0.846

-----1.436 0.718500

-----1.306 0.653550

-----1.198 0.599600

-----1.066 0.553650

+/- $1.501.026 0.513

+/- $1.500.958 0.479750

-----0.898 0.449800

-----0.846$ 0.423850

Max. Price100% ProfitCost/bu.Production

Market pricethreshold

What if production isless than 850 lbs/bu.?

700

Bulb flies/bulb/plant

Bu.

via

ble

bulb

s/ac

.

.01 .03 1.0 10.0

850

650

400

ca. 700

Your taxes at work: results of research by WA State University.

Study to determinepest level &subsequentseed production

850Mq = 98%98%

EcThresh.

Low Bulb Worm Population High

Bu.

via

ble

bulb

s/ac

re 800750700

400

EcD.

So, by developing a monitoringscheme you know when to spraythe problem.

Yea, that’s all very goodfor a Skagit Valley farm, butwhat’s it mean for the urban parkor garden?

In urban horticulture we have to think in termsof the aesthetic threshold!

Avg.PestLevel

AestheticThreshold

Pes

tNos

.

Years

Basic question: Is this an eye sore?

The Aesthetic Threshold/ Action Threshold

Economic damage thresholds & aesthetic damage thresholds:

• Crops are grown for profit, so economic damage thresholds in agriculture are based on economic criteria; pest control is done when it will improve yield and provide increased revenue that exceeds the extra cost of pest control.

• There are no formal Control Action Guidelines for pests on landscape trees and shrubs. Why? It’s difficult to define that damage level that would be intolerable, the Aesthetic Damage Threshold.

The Aesthetic Threshold varies with the attitude and knowledge of people using the landscape or garden. May depend on:

-Education level -Where the damage occurs (front yard,

back yard etc.) -The kind of damage (galls, defoliation,

potential weakening & death etc.)

On the other hand, there are plenty of pest control businesses that would help you decide the question, “do I need to control pests in my garden or landscape?”

So if you feel that the aesthetic quality of your landscaping is threatened, you must think of using an Integrated Pest Management (IPM) approach to the problem.

Avg.PestLevel

Weeks

Pes

tLev

el AeTh

:of IPM: What must I do to permanently lower the Avg.PestLevel?

When it comes down to making the control decision, only you can set your Aesthetic Damage Threshold: only then do you act! IPM solutions!

AeTh

Avg.PopLevel

NewAvg.PopLevel

(2) Sometimes the pestgets out of hand andpesticides must be used, butin terms of a surgical strike.

(1) Management components:- other varieties- biological control- cultural treatment -- mulching -- replanting (shade) -- fertilizing etc.

Weeks

Pes

tNos

.IPM

(3) Monitor!

“Here are some IPM guidelines orcomponents you may try?”

Monitoring

Has this problempassed the AeTh?

Since the intelligent and prudent use of pesticides is still considered in an IPM program, let’s learn a little about toxicology.

(1) Generally, urban-horticultural operations that use pesticides do not deal with pesticide residues on food crops. Great deal of concern, however, about residues in water and in the air (problem of drift).

(2) Nevertheless the public is terribly concerned about pesticides in general.

(3) Accordingly, it’s good to know about how the public is protected from the use and misuse of pesticides.

(4) These concerns come under the topic of toxicology & pesticide registration.

% R

esid

ue

left

on

ta

rge

t

Days after treatment

An important concern with the use of pesticidesis the residue problem: how much is left on plant.

Mechanical loss (drift)

Normal losses due to: dilution, plantenzymes, evaporation

Residues in protected places

The toxicity of a pesticide is an innate property of a product to do damage.

The toxicity of a pesticide is critical to determine the MAXIMUM ALLOWABLE RESIDUE ALLOWED ON A CROP.

“It’s not the poison that willkill me, it’s the dose!”

The toxicity tests are based on dose:response relationships. Tests use carefully bred lab rats, guinea pigs, rabbits & other animals. The rats:

• used in statistically reasoned tests.

• all the rats are statistically the same size and weight.

• bred to respond uniformly as possible.

This rat died in laboratorytoxicity teststo make the use of pesticidessafe when used byhumans.

The three main toxicity tests are:• Acute oral toxicity test

• Subacute oral toxicity test

• Chronic toxicity test

Acute Oral Toxicity -- To determine that dosage required to kill 50% of a test population of laboratory rats.

Subacute Oral Toxicity -- To determine the maximum daily dose of a pesticide that lab rats survive.

To determine the maximum daily dose without effects on lab rats, the no effect level (NOEL).

To determine the nature of effects above the NOEL level.

Chronic Oral Toxicity -- To determine effects of pesticides over the life span of lab rats - - often 2-3 generations of rats.

The “Big - 3” Oral Toxicity Tests

Acute Toxicity Test

• Test rats are fed log doses of the test-toxicant.

• Either by feeding them individually or allowing them to feed to satiation

• Most commonly the rats are force-fed via a tube.

Administration of a pesticide to a rat via a tube

Are We Safe?

• Pesticides and fertilizers are important chemicals used in urban horticulture.

• The use of these chemicals in agriculture far exceeds urban use: farmers in the U.S. contribute about $12.5 billion to the chemical industry. Use of pesticides is a huge business! Big three: cotton, corn, soybeans.

• But there are historical and enormous benefits.

Percent of Consumer Income Spent On Food

1930 1950 1970 1990 2010

• Peoplefed by onefarmer

• Number of U.S. farms(Millions)

It’s fair to say that chemicals have played a major role in freeing our people from farms for employment elsewhere.

For example:

• one person working for a company producing Roundup™

• that person can do more for agriculture than 250 people with hoes -- why?

• the herbicide can remove deep-rooted perennials which would only sprout again if their tops were clipped with a hoe, mower or cultivator

• the herbicide kills the weeds entirely - - no re-treatment.

This massive increase in agricultural production is known as the “Green Revolution.” This revolution came about:

- fertilization technology

- irrigation technology, e.g. drip technology

- crop genetics

- modern pesticides

For example: what would the prevention of fungicides do the price of key food items?

*These crops would be eliminated from U.S. markets withoutfungicide use

(1) Generally, urban-horticultural operations that use pesticides do not deal with pesticide residues on food crops.

(2) Nevertheless the public is terribly concerned about pesticides in general.

(3) Accordingly, it’s good to know about how the public is protected from the use and misuse of pesticides.

I reiterate the reasons for why we are lookinginto this arena of Toxicology & Pesticides

Are we protected?

A test with 1,000 lab rats being force-fed a test chemical at 8-dosage levels – then repeated many times, i.e. many replicates: Acute Toxicity Test.

Numbers Dying Dosage Units % CumMortality

25

75

150

250

250

150

75

25

1

2

3

4

5

6

7

8

2.5

10

25

50

75

90

97.5

99.99999

0102030405060708090

100

0 2 4 6 8

Dose

% M

ort

alit

ySigmoidal mortality response to increasing dosesof a tested pesticide

Median lethal dose is 4

The LD50 Concept

0 10 100 1000

log Doses

% C

um

Mo

rta

lity

0

25

50

100

75

LD50 is that dose in mg/kg of body weight expected to kill 50% of a test population or rats.

Why the 50% mortality level?

1. You can compare the slopes of different pesticides and see:

- which is more toxic- which has a heterogeneous or

homogeneous response

2. There is minimal statistical variation around the 50% mortality reference point.

3. By convention the 50% mortality point has been STANDARDIZED as a way to express acute oral toxicity.

See!

The LD50 Concept

0 10 100 1000

log Doses

% C

um

Mo

rta

lity

0

25

50

100

75

(A)

(B)

(C)

Uniformresponse to a reallytoxic pesticide

A less toxic pesticidebut a heterogeneousresponse (scary)

The LD100

0 10 100 1000

log Doses

% C

um

Mo

rta

lity

0

25

50

100

75

(Prod.1) test(Prod.2) test

(Prod.3) test

Leastvariation

Toxicity categories based on LD50

Oral LD50

I

Danger Poison

50 mg/kg

II

Warning

50-500 mg/kg

III

Caution

500-5000 mg/kg

IV

Caution

50-500 mg/kg

There also are dermal acute toxicitytests using ultra sensitive rabbits

Commonly used pesticidemanual used by farmersand others who deal withpesticides.

TOXICITY: LD50 945 mg/kg

An example with Orthene™:

170 lb person = 77kg

LD50 of Orthene™ = 945 mg/kg

(77kg)(945) = 72,765 mg; 73grams

The person would have to drink73gms. of pure Orthene™ to domajor harm.

4900 mg/kg

ROUNDUP,

Herbicide used by the public

The Subacute Tests

- In order to assess toxic effects that are less than the acute toxicity, such as organ damage, scientists expose rats to much lower doses than those used in determining the LD50.

- These lower doses are given to groups of test animals over an extended period, usually a tenth of their life span (about 3mo for rats).

- Subacute tests will determine the No Effect Level of test chemicals.

Th

at’s

th

en

o e

ffe

ct

lev

el!

Calculation of NOEL

LD50

log Dose (ppm)

Re

act

ion

s

The crucial effects or reactions of rats studied in the subacute toxicity tests are:

• Behavior and appearance

• Food and water consumption

• Growth rate

• Blood and urine analyses

During these tests: all affected rats are killed and autopsied for damage to vital organs and histological studies also made.

See!

During these subacute tests all organs and tissues are continually studied for:

• Teratogenicity

• Mutagenicity

• Carcinogenicity

The Delaney Amendment to the Pure Food and Drug Act of 1960 states that if any carcinogen is detected, the drug or chemical is immediately canceled.

Finally, The Maximum Tolerance Of A Residue allowed on food is = 100 times less than NOEL!

This amount of permissible residue is called the ADI (acceptable daily intake -- for the lifetime of a person).

Re-entry Statement

Precautionary StatementsHazards to Humans &Domestic Animals

The Chronic Toxicity Tests

Chronic toxicity tests are primarily aimed at learning if chemicals may produce cancers over long periods, e.g. the life span of test rats, ca. 30 months .

Other mammals also are used, e.g. primates or dogs, and tested for a year. In practice, this would be a typical rat test:

- four groups of rats (10 male, 10 female/group) - a control group - a 100 times ADI (acceptable daily intake) - a high level amount, < LD50. - an indeterminate dose

Other long term tests also are done.

Controversy:

• What if the NOEL relationship is non-linear?

• The ADI requires us to accept the threshold concept - - there is a threshold dose of a product below which there is no effect. The NOEL concept.

• If there is no threshold then even one molecule of the product might be harmful, i.e. carcinogenic

What if the NOEL is non-linear?

Non-linearity would compromise the NOEL concept.

Two theories on potential risk from carcinogens: the single-hit model and the threshold model.

• Single-hit - - even a single molecule hitting a vital part of the cell nucleus might cause cancerous growth; not likely:

- humans live all their lives in an environment bombarded by carcinogenic and mutagenic

molecules

- chances of dangerous molecules hitting a reactive DNA site are remote & there are excellent DNA repair systems

- chances of hitting a stem cell are minute; hitting any other kind of cell is of no consequence

because these cells die anyway, damaged or not

• Threshold model is supported by huge scientific data sets. It is the basis of toxicological assumptions, e.g. look at selenium, an essential trace element in humans, but at higher elevations it’s toxic. Same is true for copper, zinc, molybdenum, & cobalt.

• More than anything else, the threshold model is in contrast to the single-hit idea which must come to grips with the knowledge that animals have extensive and effective cellular repair symptoms.

0

5

10

15

20

25

30

0 10 100 1000 1000Dose

Fr/

1,00

0,00

0Allergic reactions to pesticides by humans: even if you are one of 10 allergic/million people, is it ethical to market the product?

Problem: Do rats, rabbits, dogs, or primates consistently reflect human responses? So:

- Do we know well enough the reaction of other animals to chemicals?

- What is the natural variation in biochemical responses of test animals to chemicals?

- What are the effects of minute doses on test animals? There may be effects we are simply not aware of, in spite of modern measuring techniques.

- Does ADI apply equally well to children?

Another Set of Concerns

Is this a valid scientific assumption?

“ It isn’t scientifically proper to state that a chemical is producing harmful effects until all scientific evidence thoroughly verifies it.”

The proof is therefore placed on the human population and its environment. In my view, this is unethical. Remember the Thalidomide™ case in the 1980s.

Seattle Times, May 15, 1981

The EPA gives a label to the chemical co. that wishes to manufacture a new product. The label is a legal document or license of use.

I have to readthe label, it’sthe law!

States

EPA

Invention

The Lab TestsThe Lab Tests

GreenhouseTests

Small-scaleField Tests

Large-scaleField Tests

Label Development

Registration

PerformanceTracking

PeriodicReview

Continue UseCancel

Field Use

Data Evaluation

The ChemicalCompany

General

ConfidentialStatement ofFormula

Use Classification

Disposal &SpillageRemoval

Chemistry

EnvironmentalChemistry

ResidueChemistry

ProductsChemistry& Physics

A chemical company has to give the EPA this kind of data for development and granting of a label.

Toxicity

Accidentaland OccupationalExposures

DomesticAnimalSafety

HumanSafety

Efficacy

Durationof TreatmentEffects

BeneficialInsects

Effects onTarget Organism

Data to EPA (continued)

EnvironmentalHazards

Fish &WildlifeSafety

Phytotoxicity

BeneficialInsectSafety

Effects onNon-targetOrganisms

Tolerances

In Feed

In Food

In Air &Water

Data to EPA (continued)What we talkedabout!

EPA Pesticide Registration Division

Final registration of a pesticide coststhe chemical company over, $50,000,000

EPA has a budget of over $16,500,000 in its pesticide registration and pesticideregulation departments.

It’s big MONEY