1 Pesticide Use by Sector Public Health Agriculture Forestry The - - PDF document

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BIO 4101: Pesticides and the Environment BIO 4101: Pesticides and the Environment

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What are Pests?

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Pests

• Any organism that bothers

humans

– Depends upon severity of interaction in terms of competition, health concerns

• r annoyance

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Pesticide Use by Sector

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Pesticide Use by Sector

• Public Health
• Agriculture
• Forestry
• The Home

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1 - Pesticides and Public Health

• Insects play major role in

disease transmission

• Mostly Diptera (>8 Families)
• Insects may be obligate

hosts

– e.g. Malaria in mosquitoes

• Insects may be facultative

hosts

– e.g. W Nile Virus in mosquitoes

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Public Health I: Malaria

• Probably the most devastating insect

transmitted disease in the world

• Typically tropical

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• Protozoan of

Plasmodium genus

• Causes chills, fatigue,

fever

• Infection of 300-500M/yr
• Death rate 1-10%,

depending on treatment and sp. of Plasmodium

Public Health I: Malaria

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Chemical Control of Malaria

• Most significant

intervention was with DDT

– e.g. Island of Sardinia

• 1942 = 78,000 cases
• 1951 = 9 cases after DDT

– e.g. Ceylon

• <1963 = 3M cases
• >1963 = 17 cases after DDT

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Banning of DDT

• Effectiveness of DDT as pesticide is

unparalleled

– DDT on surface would persist and continue to infect flies on contact

• After DDT was banned:

– Ceylon had 17 cases in 1963

• 1968 = 500,000 cases
• 1970 = 2M cases
• DDT still used in 3rd world although

alternatives exist (Deltamethrin)

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Public Health II: Yellow Fever

• An arbovirus (arthropod borne

virus)

• Causes jaundice and

hemorrhagic illness

• YF not huge problem but still

endemic in some places

– WHO estimates 200,000 infections/ yr with 30,000 deaths

• Outbreak in Ethiopia in 1959

killed 15,000 people

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• Modern equivalent: West Nile Virus
• Although arbovirus lifecycle not tied to

vector, treatment best when applied to vector

Public Health II: Yellow Fever

• Traditional approach:

airsprays of chemical insecticide

• Nowadays, most common is

larvicide in water (B.t.)

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Public Health III: Trypanosomiasis

• Sleeping sickness
• Known since 14th Century (Africa)
• Up to 50% mortality in some populations

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• Caused by flagellated protozoan

parasite of 2 spp. of Trypanosomiasis

• Trypanosoma ingested by TseTse

Fly (Glossina sp.)

• Parasite develops in fly and

migrates to saliva glands

• Infects human at next blood meal
• Flies hang-out under leaves,

therefore airspray not very effective

• Best control a combination of

vegetative clearing and pesticides

Public Health III: Trypanosomiasis

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Public Health IV: The Plague

• AKA “The Scourge of Man”
• Devastated entire cities and

some countries

• 14th C in Central Europe 25M

dead (1/4 of population)

• London 1666 = 70,000 deaths
• India and China (1889-1918) =

10M deaths

• Last outbreak occurred <50yrs

ago

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• Rat disease, caused by bacteria

(Pasteurella pestis) vectored by rat flea (Xenopsylla cheopis)

• Global disease control involves

combining rodenticide and insecticides in ship hulls

Public Health IV: The Plague

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Public Health V: Typhus Fever

• Caused by Ricksettia prowazeki and

transmitted by common body louse

– Pathogen picked up by louse during bloodmeal, develops in gut and released in feces – Humans infected by breathing dust or contact with wounds – In humid conditions, feces are infectious up to several months

• Treatment involves sanitation/hygiene

and louse control with pesticides

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• Associated with humans in

crowded, un-sanitary conditions

• Frequent outbreaks in combat

forces and prisons: “war fever” and “jail fever”

• WWII 1943: Naples, Italy under

siege

– Bomb shelters overcrowded and filthy – Epidemic of typhus was imminent – Arrival of Allied Forces with DDT was 1st time typhus outbreak had ever been prevented

Public Health V: Typhus Fever

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2 - Role of Pests in Agriculture

• Three main categories:

– Insects – Diseases – Weeds

• Agriculture is largest user of pesticides

by sector

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Agricultural Use (%) by Sector

1960 1970 1980 1990 2000 2010 Herbicides 20 35 41 45 47 46 Insecticides 37 37 35 28 27 28 Fungicides 40 27 19 20 21 21 All Others 4 6 6 7 7 6

Market Value ($ M US) 800 2,00 11,600 28,000 38,000 50,000

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Contribution of Pesticides to Cash Crops

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Weeds 13.2% Diseases 13.3% Animal pests 15.6% Weeds 16.4%

Animal pests 7.1% Diseases 4.2%

Actual losses US$ 244 billion 42.1% 27.6% Production without crop protection 30.3% Attainable production - US$ 579 billion Losses prevented by crop protection US$ 160 billion

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Insects as Agricultural Pests

• Estimated that 75% of all animals are

insects (mostly beetles)

– Not surprising there are so many ecological interactions with insects – Insects are mostly beneficial, small number are pests

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Types of Damage Caused by Insects

• Depends largely on

morphology of mouthparts

• Chewing insects

– Defoliators, borers, leaf miners, root feeders

• Sucking insects

– Distort plant growth, stippling

• n leaves, burning of leaves

(secretion of toxins)

• May also be vectors of

disease

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Types of Damage Caused by Insects

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• Insect pests usually cause

incremental damage

– Calculate EIL and ET to know when to intervene

• Sometimes infestations
• ccur and cause huge

losses very quickly

– e.g. locust swarms – e.g. armyworm “marching” across country

Insects as Agricultural Pests

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Effect of Insects on Food Production

• In grain crops, insects may cause a

decrease in yield but do not impact harvest quality

• In fruit and vegetable crops, insects may

cause yield reduction and affect harvest quality due to aesthetic expectations

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For example, Apples (Malus spp.)

• Important crop in Ontario
• Plagued by codling moth (Cydia

pomonella), red-banded leafroller (Argyrotaenia velutinana) and apple maggot (Rhagoletis pomonella)

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A) Codling Moth

• 2 generations/yr.
• Gen 1: adults emerge in spring, mate and

lay eggs in upper leaves

• Larvae migrate to fruit and chew inside
• Larvae eat inside fruit, many fruit fall to

ground with insects in development

• They leave apple, find shelter and pupate

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• Gen 2: adults emerge, mate and lay eggs near

fruit

• Larvae attack fruit as they mature in late summer
• Therefore, 2 phases of damage

– Without intervention, losses can be 20-90%

• Most damage not visible

– Therefore, need to monitor – Pesticides only useful before larvae enter fruit

A) Codling Moth

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B) Red-banded Leafroller

• Also 2 generations per year but occurs

two weeks before codling moth

• Early generation feeds mostly on leaves,

later generation on fruit

• Complicates treatment with pesticides

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C) Apple Maggot

• Most destructive pest of apples
• May have 85% loss if not treated
• Overwinters as pupae in soil
• Adults emerge in early summer, mate

and lay eggs just beneath skin of fruit

• Larvae burrows as they eat, leaving

series of trails (railroad worm)

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For example, Cotton (Gossypium sp.)

• Historically, largest user of pesticides among

agricultural crops

– 25% of world’s insecticides

• Plagued by cotton boll weevil (Anthonomus

grandis)

– Introduced from Mexico in late 19th century – Adults feed on bolls, lay 200 eggs which hatch weeks later – Damage is extensive – Losses of $300M/yr

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• Historically, cotton farming has employed all

types of pesticides available

– 1920s: crop dusting of calcium arsenate – 1950s: DDT (bollworm quickly developed resistance) – Resistance also found for dieldrin, heptaclor, endrin and toxaphene

• Nowadays, genetically modified cotton for

resistance may reduce pesticide use by as much as 80%

For example, Cotton (Gossypium sp.)

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Plant Disease in Agriculture

• Over 100,000 plant diseases in NAm, 50,000 of

which are highly destructive

– 8000 spp. of fungi – 500 spp. of nematodes – 250 viruses – 160 spp. of bacteria

• On a per crop basis:

– 115 diseases on tomato – 196 on potato – 77 on wheat – 112 on corn – 200 on apples

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Plant Diseases

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Plant Diseases

• Pathological: caused by a

living microorganism or virus

• Physiological: caused by

a continued deficiency of a nutrient

• Losses not as dramatic as

from insects, not as

• bvious as from weeds

– Often insidious, difficult to detect

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Plant Diseases

• Can attack plants from the very

beginning: planting of seeds

– Especially true for large seeded vegetables (e.g. peas, beans, corn, curcurbits) – Many seeds fail to germinate due to infection

• Paradox: need early planting to

maximize growing season but cool, moist conditions promote development of disease

– Therefore, many seeds coated in fungicides

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Stages of Disease Development

• 1) Inoculation

– Arrival of pathogen (e.g. egg, spore, larvae…)

• 2) Incubation

– Development and growth of pathogen population

• 3) Infection

– Pathogen enters plant and begins affecting it

• Disease occurs when plant responds

– Wilting, cells die etc…

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Conditions Required For Disease to Occur

• 3 steps are required for diseases

– 1) susceptible host plant – 2) disease producing agent (pathogen) – 3) environment favourable to disease development

• Eliminate any of these to prevent disease
• ccurrence

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How Disease is Controlled

• 1) Exclusion

– Prevent disease from coming into area

• 2) Eradication

– Eliminate pathogen from the area

• 3) Protection

– Place protective barrier between pathogen and area of interest (usually chemical)

• 4) Resistance

– Develop and use plant varieties that not susceptible to the disease

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Weeds in Agriculture

• Weed: any plant growing

in a place where it is unwanted

– May be desired elsewhere

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Many Hundreds of Species of Weeds

• In average hectare of

agricultural soil, may be several million weed seeds

• If only 10% germinate, still

have hundreds of weed plants per sq. meter

– Competition for nutrients, light, water

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Weedy Characteristics

• Related to r-selected life history pattern

– High capacity for dispersal (colonization) – Potential for seed dormancy – Fast growth – Production of many offspring – Good competitors – Shade intolerant

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Crop Injury From Weeds

• Reduced yields (competition)
• Reduced quality (contamination)
• Increased production costs

(management)

• Poisonous or

irritating

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Competition From Weeds

• Wild mustard requires

2X as much nitrogen and 4X as much water as oats

• Ragweed has 3X water

and nutrient requirements as corn

– Also causes allergies

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Crop Losses to Weeds

• Experimental plots:

– Corn in Illinois lost 81% – Corn in Minnesota lost 51% – Soybeans in Nebraska lost 45%

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In Arid Areas (ex. Prairies)

• Where water is limiting, crops sometimes

rotated on 3 year cycle

– 2 years production, 1 year fallow – Conserves soil moisture for crops – Creates need to control weeds in fallow year

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Herbicide Use in Agriculture

• Corn (most significant)
• Other grain plants

– Wheat, barley, oats, rye

• Brush control in pastures and rangelands

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Most Common Herbicides

• Accounted for approx. 95% (in decreasing order
• f importance Internationally):

– Atrazine – Propachlor – Alachlor – 2,4-D – Butylate

Currently Glyphosate is #1 in USA

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Cosmetic Bans of Domestic Pesticides

• 140 municipalities across

Canada Have some kind of ban in place

• Entire Province of Quebec

since 2003

– Currently have lowest rates

• f pesticide application in

Canada (50% decrease from 1994 levels)

• Ontario followed suit in

2009

– Exceptions for public health and safety, agriculture, forestry and golf courses

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Vertebrate Pests in Agriculture

• Many species of birds and mammals are

pests but pesticides rarely used

– Trapping, shooting, noisemakers, scarecrows etc…

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Rodents

• Rats and mice are big pests of grain

storage

– Rodenticides used but must be tightly controlled around feed grain to avoid contamination – Most common is Warfarin (mostly used in home)

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Predators

• Pests of livestock

ranchers

– Coyotes, wolves prey on sheep, calves, poultry

• Sometimes pesticides have been used in

the past to poison predators (e.g. strychnine)

– Cause non-target problems because carrion also poisonous

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Birds

• Can be pests of fruit and grain crops

– Big losses from Robins and other songbirds in blueberry production – Big losses in corn from blackbirds (e.g. red- winged blkbrd, starlings, cowbirds)

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Pests in Forestry

• In North America, 1/3 of

area covered by forest

– Used for timber, recreation, aesthetics

• In Canada, there are 3

hectares of forest for each hectare of cultivated land

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Forest Resources, Nat.Res. Canada

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Millions of ha Harvested forest; 0.9 Managed forest; 144.6 Forest land; 309.8 Total forest and wooded land 401.9 Total land 909.4

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• Many forest pests, particularly insects

and disease

• Losses may be due to wood destroyed or

from lost potential due to growth inhibition

Pests in Forestry

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Temporal Dynamics

• Forests are long-

lived, therefore often have cyclical

• utbreaks of pest

populations

• For example,
• utbreaks of Spruce

Budworm follow several years of dry, mild spring weather

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Major Insect Pests in Forestry

• Gypsy Moth (Lymantria dispar)

– Introduced from Eurasia in 1869, hoping to create silk industry in Massachusetts – Silk industry failed but moth proliferated – Less than 20yrs later was defoliating New England deciduous trees

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• Spruce Budworm (Choristoneura spp.)
• In Canada, have been 6 major outbreaks

since 1700

• Synchrony between budworm and fir-

spruce-birch forests of E Canada and Maine

Major Insect Pests in Forestry

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Spruce Budworm Outbreaks

• Outbreak in 1877 wiped out entire forest but

understory regenerated

• In 1912, understory was a mature forest
• After several dry seasons, fir forests completely

wiped out by 1919

• Another outbreak occurred in 1949-1958 when

previous understory became mature forest

• Post WWII attacks less severe due to chemical

intervention

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Globalization and Exotic Pests

• Asian long-horned beetle

(Anoplophora glabripennis)

• Introduced from China to

Brooklyn in1996

• Larva burrow in hard-wood

trees

– Maple, birch, willow etc.

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Diseases in Forestry

• For the most part, pesticides have not

played major role in regulating disease in forests

• 2 exceptions

– White Pine Blister Rust – Dutch Elm Disease

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White Pine Blister Rust

• Cronartium ribicola (Fungi)
• Requires 2 hosts to complete life-cycle
• Spores produced on Ribes (currants)

released into wind and infect trees

• Attacks 5-needled pines
• High degree of mortality (100%)

in young pines

• Pesticides used against Ribes

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Dutch Elm Disease

• 3 species of Ophiostoma

fungus

• Introduced to NAm in

1930

• Attacks almost all species
• f Elm (Ulmus)
• Fungus grows and

mycelium clogs vascular tissues, choking tree

– Slow, progressive death

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• Transmitted by 3 species of Bark

Beetles

• Bark Beetles bore into dead or decaying

wood and lay eggs

• Larvae burrow while developing
• Emerging adults carry spores to healthy

trees for infection

• Chemical pesticides are

used to control the beetle vectors

Dutch Elm Disease

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Herbicides in Forestry

• Mostly restricted to roads, rights-of-way,

powerlines, railways

• Also used to clear re-growth after clear-cut

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Herbicides in Forestry

• For weeding after clear cuts

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Pesticides in the Home

• Although agriculture is largest user, domestic

use is most frequent

• Most important domestic pests:

cockroach, rats, termites

– Also: fleas, silverfish, mice, ants, clothes moths

• Lawns may be attacked by grubs, beetles,

weevils, webworms, mice, moles, rabbits

– Ontario has passed a law banning the cosmetic use of pesticides (2009), following Quebec

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Pesticide Market Breakdown (USA)

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70 PROFESSIONAL MARKET

Insecticides

Herbicides Rodenticides Fungicides Other

CONSUMER MARKET

Insecticides Herbicides Rodenticides Fungicides

Total market = $1.8 Billion Total market = $1.8 Billion