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THE TROUBLE WITH PESTS - Moore 1

LIVING WITH THE EARTH

Objectives for this Chapter

• A student reading this chapter will be able to:– 1. Discuss and define the term pest. – 2. List, differentiate and classify the major

arthropod pests to the Order level.– 3. Discuss and describe the general structure

and development of insects and arthropod pests.

• A student reading this chapter will be able to:– 4. List and describe the major arthropod and

mammalian vectors of disease including kissing bugs, flies, mosquitoes, fleas, sucking lice, ticks, mites, rats, and mice.

– 5. Describe and provide specific methods for rodent control.

• A student reading this chapter will be able to:– 6. Discuss and describe the purpose and function of

pesticides and the issues of ecological damage, pesticide resistance, and adverse health effects.

– 7. List and describe the major classes of arthropod and rodent pesticides, their mechanism of toxicity, and some alternatives to chemical pesticides.

THE TROUBLE WITH PESTS

INTRODUCTION– The prospect of hunger and starvation is a

powerful motivation in adjusting attitude towards what is food and what is a pest.

WHAT ARE PESTS?

• Pests are unwanted plants and animals.• Any living thing that negatively affects

human interests.

Human Interests

• (1) a loss of resources such as agricultural crops, food and property damage, and damage to lawns and gardens;

• (2) agents of disease; and • (3) sources of annoyance and discomfort.

WHAT ARE PESTS?

• The most unwelcome pests from a public health perspective tend to include arthropods and rodents.

WHAT ARE PESTS

• The arthropods (phylum Arthropoda) are invertebrate animals with jointed and paired appendages, a chitinous exoskeleton, and segmented bodies.

• It is the largest animal phylum with over 700,000 species (Fig. 6-1a,b)

Fig. 6-1aFrom the slide collection of Dr. John Edman, Entomology, Fernald Hall, Umass, Amherst

Fig. 6-1bFrom the slide collection of Dr. John Edman, Entomology, Fernald Hall, Umass, Amherst

WHAT ARE PESTS

• Insects, ticks and mites are involved in the majority of important human vector-borne diseases, and most of these diseases cannot be prevented by vaccines or chemotherapy.

WHAT ARE PESTS

• Early success in the control of insect vectors has been met with reversals as:– (1) insects have developed resistance to

insecticides; – (2) insect control programs have been halted or

underfunded;

WHAT ARE PESTS

• Early success in the control of insect vectors has been met with reversals as:– (3) the use of less expensive pesticides such as DDT

have been reduced because of environmental concerns and political pressures;

– (4) the combination of poverty and overpopulation has lead to poor sanitation with greater opportunity for insect proliferation;

WHAT ARE PESTS

• Early success in the control of insect vectors has been met with reversals as:– (5) destruction of forested areas has eliminated

natural insect predators; and – (6) climate changes, including warming trends,

has promoted increases in some insect populations.

What Are Pests?

• In order to develop workable biological, physical, or chemical controls, it is critical to understand the biology and mechanisms for the spread of disease by these organisms.

INSECTS AND OTHER ARTHROPODS

• General Structure and Development– Most insects start their life cycle with the

fertilization of an egg, and they pass through either a complete or incomplete metamorphosis.

General Structure and Development

• Incomplete metamorphosis – Refers to insects such as roaches, body lice, and

grasshoppers, that go through three developmental stages including egg, nymph, and adult stages.

• Complete metamorphosis– Mosquitoes, flies, and butterflies go through

complete metamorphosis and pass through four developmental stages including egg, larvae, pupa, and adult stages.

• Molting• Exoskeleton• Spiracles

• The hardened outer body wall of the exoskeleton may be covered with hairs, scales, or spines, and is normally divided into segments joined by flexible intersegmental structures (Fig. 6-2).

Fig. 6-2

• Biological Vector– In many instances, the microbial disease agents

go through a developmental stage in the vector involving sexual reproduction (i.e., malaria).

– In these instances, the vector is known as a biological vector.

Bedbugs and Kissing Bugs• Insects belonging to this

category have three pairs of jointed legs, sucking mouth parts, wings or wing pads, a segmented proboscis, and belong to the order Hemiptera.

Bedbug

• Bedbugs hide in bedsprings, mattresses, and cracks in the wall coming out at night to feed on humans and warm-blooded animals (Fig. 6-3b).

Kissing Bugs

• The kissing bug is the arthropod vector for American trypanosomiasis or Chagas’ disease caused by the flagellated protozoan parasite Trypanosoma cruzi (Fig. 6-3a).

• Flies belong to the same order of insects (Diptera) as mosquitoes, Adult flies have one pair of functional wings and three distinct body parts including the head, thorax and abdomen (fig. 6-4).

Fig. 6-4

From the slide collection of Dr. John Edman, Entomology, Fernald Hall, Umass, Amherst

• The common house fly, Musca domestica, is an important vector of infectious disease organisms and foodborne illnesses.

• Diseases that may be mechanically transmitted by flies include: – cholera, bacterial and amoebic dysentery,

typhoid and paratyphoid fevers, salmonellosis, hookworm, pinworm, and whipworm.

• Lay eggs onto garbage, manure, or organic material

• Undergo complete metamorphosis

• Biting flies have been responsible for the transmission of a number of diseases including sandfly fever, onchocerciasis(blinding filariasis), African sleeping sickness, deerfly fever ( a form of tularemia), and loaisis (African eyewormdisease).

The Control of Flies

• Elimination of breeding materials• Tight fitting screens• Air shields• DDVP resin strips

Mosquitoes

• Mosquitoes have one pair of wings with scales, belong to the order Diptera (2 wings).

• Females are characterized by having piercing/sucking mouth parts with an elongated proboscis.

Mosquitoes

• Depending on the species, the eggs may be deposited in still water such as swamps, wet depressions, or in the collected water of old tires or containers.

• Mosquitoes undergo complete metamorphosis (Fig. 6-5).

Mosquitoes

• Once a host is found, the female mosquito takes a blood meal during which time it injects saliva into the skin.

• The time required for digestion of the blood meal, laying more eggs, and then seeking another blood meal may be as little as two days.

Mosquitoes

• Many of the species of public health interest belong to the genera Anopheles, Culex, andAedes.

• Aedes aegypti is an important vector for yellow fever.

Mosquitoes

• Aedes albopictus (Asian Tiger mosquito) inadvertently imported from Japan to Texas.

• Bites severely, survives cold winters, and is capable of transmitting the agents of dengue fever and dengue hemorrhagic fever, the encephalitides group of viruses, and yellow fever.

Mosquitoes

• Aedes– Yellow Fever and Dengue Types

• Anophelene– Malaria

• Culex– Viral Encephalitis

Mosquito Control

• Elimination of stagnant water• Carbaryl and Malathion• Screens• Repellants, DEET (Diethyl toluamide)

• Fleas are true insects with three pairs of legs and no wings.

• Several species of fleas have the ability to bite humans (Pulex irritans), dogs and cats (Ctenocephalides sp.), and rats (Xenopsyllacheopis) (Fig. 6-6).

Fig. 6-6From the slide collection of Dr. John Edman, Entomology, Fernald Hall, Umass, Amherst

• The female flea takes a blood meal from its host, mates, and then lays eggs.

• eggs drop to the nearest surface such as carpet, or furniture, where they undergo complete metamorphosis to an adult stage within 2-3 weeks.

• Their ability to take blood meals and move swiftly among and humans makes them important vectors of disease including plague (Yersinia pestis), murine typhus, tularemia, and even salmonellosis.

• The rat flea carries the plague bacillus in its intestinal tract, spreading it from rat to rat and from rat to human (Fig. 6-7).

Fig. 6-7

Flea Control

• Usually in domestic animals and domiciles includes:– Pesticidal dusts usually containing carbaryl or

methoxychlor

• Lice have no wings, a dorso-ventrally depressed abdomen (flat), and have legs adapted for clasping hairs and undergo incomplete metamorphosis (Fig. 6-8a,b).

• Three kinds of human lice:– The head louse (Pediculis humanis capitis)– The body louse (Pediculis humanis corporis) – Crab louse (Pthirius pubis).

• In addition to spreading epidemic typhus, lice also cause trench fever (Rickettsiaquintana), and relapsing fever (spirochetes belonging to the genus Borrelia).

Roaches

• Cockroaches are true insects having three pairs of legs, one pair of antennae, and chewing mouth parts (Fig. 6-9).

Fig. 6-9

Roaches

• Undergo incomplete metamorphosis • The eggs are usually encased in a capsule

and carried for a few days• Prefer the dark

Roaches

• No specific disease outbreaks have been attributed to roaches but they may serve as vectors and create a level of discomfort for most people.

Roach Control

• Eliminate food sources• Borax powders• Organophosphate poison, malathion

Ticks and Mites

• Ticks and mites have four pairs of legs, no antennae or wings, an belong to the class Arachnida.

• A shorter abdomen and the absence of a constriction between the cephalothorax and abdomen place organisms such as ticks and mites in the order Acarina.

• Mites do not have a clearly differentiated head, thorax, and abdomen (Fig. 6-10).

• The mite Sarcoptes scabiei burrows under human skin to lay its eggs.

• Mites are transmitted through close personal contact with an infected person.

Mites Infestations

• Dogs develop a condition called mange.• Humans develop Scrub typhus, certain

forms of hemorrhagic fever, and encephalitis.

Mite Control

• Keep area clean• Plenty of sunlight• Pyrethrum bomb, and malathion

• Belong to the class Arachnida• They have four pairs of legs, no antennae,

and a fused head, thorax and abdomen (Fig. 6-11).

Ticks are particularly adapted to feed on blood by:

• (1) the use of barbed feeding organs that pierce the skin to reach the blood and also anchor the tick;

• (2) a flexible leathery body that easily distends when filled with blood: and

• (3) uniquely adapted pharyngeal muscles for sucking blood.

Two types of Ticks

• Soft (family Argasidae) • Hard (family Ixodidae) ticks

• Ticks undergo complete metamorphosis and have a fairly complex cycle such as the deer tick, Ixodes scapularis, which is the vector of lyme disease caused by the spirochete Borrelia burgdorferi (Fig. 6-12).

Fig. 6-12

From the slide collection of Dr. John Edman, Entomology, Fernald Hall, Umass, Amherst

• A tick may transmit disease– Mechanically or– Transstudial (tick - egg - tick)

Disease Transmitted by Ticks

• (1) Rickettsial diseases including tularemia, Q fever, and Rocky Mountain spotted fever

• (2) The disease caused by Borrelia sp. including lyme disease and relapsing fever;

• (3) viral diseases such as Colorado tick fever,; and

• (4) bacillus diseases such as Pasteurellatularensis.

Tick Control

• Humans– Cover skin when at risk to exposure– DEET insect repellant

• Domestic animals– Flea and tick collars

Rodents and Pests

• Rodent Characterisitcs– Rats and mice are members of the order

Rodentia, which include mammals with teeth and jaws adapted to gnawing.

Rodents and Pests

• The Roof Rat, (Rattus rattus) (Fig. 6-13)– Lives in attics or barns– Pointed snout– Tail longer than it’s body– Weighs between 8-12oz– Length with tail 8-17in

Fig. 6-13

Rodents and Pests

• The Norway Rat , (Rattus norvegicus) (Fig. 6-14)– Lives under foundation, along river banks,

sewers, between walls– Blunt snout– Tail shorter than it’s body– Weighs up to 16oz– Length with tail 12-18in

Fig. 6-14

Rodents and Pests

• The House Mouse – Lives in close contact with humans

(commensal)• The Deer Mouse

– (Peromyscus maniculatis) is a vector of the hanta virus.

Importance as Pests and Vectors

• (1) they harbor a variety of organisms that can produce diseases in humans;

• (2) they produce crop damage throughout the world;

Importance as Pests and Vectors

• (3) they eat and contaminate food produce and cause structural damage;

• (4) afflict harm directly by biting humans; and

• (5) cause extreme discomfort in some people by their visible presence.

Rodent Control

• Establish presence (Fig. 6-16)• Rodent Proofing • Poisoning or trapping

Fig. 6-16Source: Training materials from HEW

PESTICIDES

• History– Pests compete with humans for food, serve as

vectors of disease, destroy crops or depress their market quality, cause structural damage to buildings and homes, and attack people directly causing annoyance, injury, or even death.

PESTICIDES

• History– 1800s

• Copper arsenate compounds (Paris Green) and lead arsenate (Bordeaux mixture) were introduced as fungicides and pesticides.

– WWII• DDT

PESTICIDES

• History– 1970s

• Realization of detrimental effects on ecology and human health.

PESTICIDES

• Present Day Problems– (1) the resistance of vectors to pesticides; – (2) the adverse health and ecological effects of

pesticides; and – (3) the proliferation of pesticides globally.

Insect Resistance

– From 1970 to 1980, the number of arthropods resistant to insecticides nearly doubled from 224 to 428 while the numbers of resistant species of rodents, bacteria, fungi, and weeds are increasing as well.

Insect Resistance

• Physiological Resistance– 1) enzymatic detoxification of pesticides into a

less harmful form: – (2) reduced permeability of exoskeleton to

pesticides; and – (3) storage or excretion of pesticides without

Insect Resistance

• Behavioral Resistance– (1) landing less frequently or changing landing

areas: or – (2) avoidance of baits such as fly-paper.

The Health and Ecological Effect of Pesticides

• Humans are exposed to pesticides through: – (1) contaminated drinking water; – (2) eating foods contaminated with pesticides; – (3) pesticide use in the home, garden or lawn: – (4) exposure on transcontinental flights;

The Health and Ecological Effect of Pesticides

• Humans are exposed to pesticides through: – (5) use in agriculture; – (6) in the production of pesticides; and – (7) in other occupations.

Effects of Pesticide Poisonings

• Most Acute or one-time exposures– Headaches, dizziness, muscular weakness, and

fatigue• Chronic or low-level pesticide exposure

– Uncertain, but cancer and/or reproductive are possible problems associated with organochlorine pesticides.

Children at Risk

• Children are exposed to pesticides through: – (1) prenatal maternal exposure; – (2) food and water sources; – (3) presence in agricultural, fields with parents,

or working the fields themselves;

Children at Risk

• Children are exposed to pesticides through: – (4) contact with residues on parents’ clothing;

or – (5) exposure to common household pesticides

while in the home (Table 6-1).

Table 6-1Adapted from USEPA.24

Exposures in LDCs

• Reasons for higher incidence of pesticide poisonings in LDCs– (1) failure to use protective clothing when

applying pesticides;– (2) workers may be in the field during pesticide

spraying;– (3) pesticides are being used in LDCs that are

banned or severely restricted in the developed countries;

Exposures in LDCs

• Reasons for higher incidence of pesticide poisonings in LDCs– (4) pesticide containers are often recycled to

store food, milk, or cooking oil; and – (5) pesticide products are labeled in languages

not readable to the native populations

Ecological Concerns

– Much more than 1.1 billion pounds of pesticides are used in the United States each year with more than five times that amount used globally.

Ecological Concerns

– Pesticide residues, especially of the persistent organochlorines, are now detected in the tissues of animals in virtually every location on earth from the Antarctic to the everglades, small new England streams, to the deepest ocean trenches.

Ecological Effects

– Disrupted the endocrine system of bird, fish, mammals

– Decreased fertility– Increased abnormal behaviors– Feminization and Masculinization

Types of Pesticides

• Insecticides– (1) act as contact poisons by penetrating the

foot pads or body wall; – (2) enter the insect breathing pores as a

fumigant; – (3) act as a stomach poison after ingestion: or – (4) desiccate (dryout) the body wall causing it

to crack or break.

Insecticides

• Organochlorines• Organophosphates• Carbamates

Organochlorines

• Dichlorophenylethanes– DDT (Fig. 6-19)– Bioaccumulation– Caused thinning egg shells in fish eating birds

Fig. 6-19

Organochlorines

• Hexachlorocyclohexanes– Lindane (Fig. 6-20)– Treatment for ectoparasites.

Fig. 6-20

Organochlorines

• Chlorinated Cyclodienes– Chlordane (Fig. 6-21)– Stomach poisons, fumigants, contact poisons– Used against roaches, silverfish ants, and

termites.– Most were suspended by the EPA in the 1970s

Fig. 6-21

Organochlorines

• Chlorinated Cyclodiene– Kepone (Fig. 6-22)

• Neurological damage among workers in Virginia• Chesapeake Bay

Fig. 6-22

Organophosphates

• Parathion (Fig. 6-23)– Most likely to be involved with human

fatalities.• Cholinesterase inhibitors (Fig. 6-24)

Fig. 6-23

Fig. 6-24a

Fig. 6-24b

Carbamates

• Derivatives of carbonic acid are contact poisons that inhibit cholinesterase in a manner similar to organophosphates.

Botanical and Biological Insecticides and other

Alternatives

• Naturally derived alkaloids• Bacteria• Fungal Spores• Integrated Pest Management (IPM)

Herbicides

• Atrazine, alachlor (Fig. 6-25)– Destroy the plants by stimulating abnormal

growth and interfering with the transport of nutrients.

Fig. 6-25

Rodenticides

• Warfarin (Fig. 6-26)– Inhibits prothrombin synthesis.– Animal bleeds to death

Fig. 6-26

living with the earth - umasspeople.umass.edu/~envhl565/powerpoint/powerpoint s/slide06.pdf ·...

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