Chapter 8: Ecosystem Degradation Pests and Pesticides

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1 Chapter 8: Ecosystem Degradation Pests and Pesticides 1

2 What are pests? Unwanted plants and animals Any living organism that negatively affects human interests cause loss of resources agricultural crops food and property damage damage to lawns and gardens agents of disease sources of annoyance and discomfort 2

3 What are pests? Arthropods (phylum Arthropoda) invertebrate animals with jointed and paired appendages, a chitinous exoskeleton, and segmented bodies largest animal phylum with over 700,000 species Rodents (mammal order Rodentia) rats and mice (among others) mammals with teeth and jaws adapted to gnawing 3

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6 What are pests? Insects, ticks and mites involved in the majority of important human vector-borne diseases role as biological vectors for microbial disease organisms or parasites most of these diseases cannot be prevented by vaccines or chemotherapy 6

7 Why the problem is on the rise Insects have developed resistance to insecticides Insect control programs have been halted or underfunded The use of less expensive pesticides such as DDT have been reduced because of environmental concerns and political pressures 7

8 Why the problem is on the rise The combination of poverty and overpopulation has lead to poor sanitation with greater opportunity for insect proliferation Destruction of forested areas has eliminated natural insect predators Climate change has promoted increases in some insect populations 8

9 Why the problem is on the rise 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 9

10 Insects and other arthropods General structure and development most insects start their life cycle with the fertilization of an egg pass through either a complete or incomplete metamorphosis 10

11 Insect structure and development Incomplete metamorphosis three developmental stages egg nymph adult Dragonflies are beneficial insects! e.g., cockroaches, body lice, and grasshoppers 11

12 Insect structure and development Complete metamorphosis four developmental stages egg larvae pupa adult Ladybugs and butterflies are beneficial insects! e.g., mosquitoes and flies 12

13 Insect structure and development Exoskeleton: hardened outer body wall may be covered with hairs, scales, or spines normally divided into segments joined by flexible intersegmental structures 13

14 Bedbugs and kissing bugs Bedbugs bedsprings, mattresses, and cracks in the wall come out at night to feed on humans and warm-blooded animals 14

15 Bedbugs and kissing bugs Kissing bugs or assassin bugs vector for American trypanosomiasis or Chagas disease caused by the flagellated protozoan parasite Trypanosoma cruzi acute local swelling can progress to chronic disease of heart and intestines 15

16 Flies Common house flies (Musca domestica) important vectors of infectious disease organisms and foodborne illnesses lay eggs onto garbage, manure, or organic material undergo complete metamorphosis 16

17 Diseases transmitted by flies cholera bacterial and amoebic dysentery typhoid and paratyphoid fevers salmonellosis hookworm pinworm whipworm sandfly fever onchocerciasis (blinding filariasis) African sleeping sickness deerfly fever (a form of tularemia loaisis (African eyeworm disease) 17

18 Controlling fly populations Elimination of breeding materials Tight fitting screens Air shields DDVP resin strips 18

19 Mosquitoes Females have piercing/sucking mouth parts with an elongated proboscis 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 Undergo complete metamorphosis 19

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22 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 22

23 Mosquitoes Anopheles, Culex, and Aedes public health problems Aedes aegypti : vector for yellow fever Aedes albopictus (Asian tiger mosquito) inadvertently imported from Japan to Texas bites severely and survives cold winters capable of transmitting the agents of dengue fever and dengue hemorrhagic fever, the encephalitides group of viruses, and yellow fever 23

24 Controlling mosquito populations Elimination of stagnant water Use of pesticides: carbaryl and malathion Screens Repellents (e.g., DEET diethyl toluamide): prevent blood meal required for egg development 24

25 Fleas Important species for public health Pulex irritans: humans Ctenocephalides sp.: dogs and cats Xenopsylla cheopis: rats 25

26 Fleas 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 26

27 Fleas Their ability to take blood meals and move swiftly among animals and humans makes them important vectors of disease plague (Yersinia pestis) murine typhus tularemia salmonellosis 27

28 Fleas Rat fleas carry the plague bacillus in their intestinal tracts, spreading it from rat to rat and from rat to human 28

29 Controlling flea populations In domestic animals and homes use of pesticidal dusts containing carbaryl (Sevin) or methoxychlor brewer s yeast orange oil 29

30 Lice No wings, a dorso-ventrally depressed (flat) abdomen, legs adapted for clasping hairs undergo incomplete metamorphosis 30

31 Lice Three kinds of human lice head louse (Pediculis humanis capitis) body louse (Pediculis humanis corporis) crab louse (Pthirius pubis) 31

32 Diseases associated with lice Epidemic typhus Trench fever (Rickettsia quintana) Relapsing fever (spirochetes belonging to the genus Borrelia). 32

33 Cockroaches Chewing mouth parts 33

34 Cockroaches Undergo incomplete metamorphosis The eggs are usually encased in a capsule and carried for a few days Prefer the dark 34

35 Cockroaches No specific human disease outbreaks have been attributed to roaches may serve as mechanical vectors, capable of carrying disease from one place to another (e.g., sewer to house) associated with 32 bacterial,17 fungal-related and three protozoa- related illnesses, as well as two viruses but haven t been directly shown to transmit these diseases Allergens Create a level of intense discomfort for most people 35

36 Controlling cockroach populations Eliminate food sources Borax powders Organophosphate poison, e.g., malathion 36

37 Ticks and mites Four pairs of legs, no antennae or wings Acarina: shorter abdomen and the absence of a constriction between the cephalothorax and abdomen 37

38 Mite diseases Humans Sarcoptes scabiei burrows under skin to lay its eggs transmitted through close personal contact with an infected person Scrub typhus certain forms of hemorrhagic fever and encephalitis Dogs: mange 38

39 Controlling mite populations Keep area clean Plenty of sunlight Pyrethrum bombs, malathion 39

40 Ticks Four pairs of legs, no antennae, and a fused head, thorax and abdomen 40

41 Tick adaptations Barbed feeding organs that pierce the skin to reach the blood, anchor the tick Flexible leathery body that easily distends when filled with blood Uniquely adapted pharyngeal muscles for sucking blood 41

42 Ticks Two types of ticks 42

43 Ticks Undergo complete metamorphosis Complex life cycle, e.g., deer tick (Ixodes scapularis) vector of lyme disease caused by the spirochete Borrelia burgdorferi 43

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45 Diseases transmitted by ticks Rickettsial diseases including tularemia, Q fever, and Rocky Mountain spotted fever Diseases caused by Borrelia sp., including lyme disease and relapsing fever Viral diseases such as Colorado tick fever Bacillus diseases such as Pasteurella tularensis. 45

46 Controlling tick populations Humans cover skin when at risk to exposure DEET insect repellant Domestic animals use of flea and tick collars 46

47 Rodents as pests Roof rat (Rattus rattus) attics or barns pointed snout, tail longer than body weight 8-12oz, length with tail 8-17in 47

48 Rodents as pests Norway rat (Rattus norvegicus) under foundations, along river banks, sewers, between walls blunt snout, tail shorter than body weight up to 16oz, length with tail 12-18in 48

49 Rodents as pests House mouse (Mus musculus) lives in close contact with humans commensal Deer mouse (Peromyscus maniculatis) vector of the hanta virus 49

50 Rodents as pests and vectors Harbor a variety of organisms that can produce diseases in humans Damage crops throughout the world Eat and contaminate food Cause structural damage Afflict harm directly by biting humans Cause extreme discomfort in some people by their visible presence 50

51 Controlling rodent populations Establish presence Rodent proofing Poisoning or trapping 51

52 Chapter 8: Ecosystem Degradation Pests and Pesticides 52

53 Pesticides Intentional environmental application Benefits increased production of food and fiber protection from pests spoilage prevention human disease prevention 53

54 Accidental human exposures Bhopal, India 1984 methyl isocyanate 2800 killed Turkey and Iran 1960s mercury fungicide 100s killed 54

55 Pesticide classification Use categories Human health: control disease vectors Malaria: Plasmodium (parasitic protozoan) carried by Anopheles mosquitoes 55

56 Pesticide classification Use categories Human health: control disease vectors Yellow fever / dengue / encephalitis / West Nile: viruses transmitted by Aedes, Culex Bubonic plague: Pasteurella bacteria carried by rat fleas 56

57 Pesticide classification Use categories Agriculture worldwide crop losses to pests (1990s) 24% of wheat 46% of rice 35% of corn 55% of sugar cane 37% of grapes 28% of all vegetables types used U.S.: herbicides, insecticides, fungicides Europe: fungicides 57

58 Pesticide classification Use categories Forestry control of insect defoliations, e.g., spruce budworm resistance to pesticide use in forests idea of pristine wilderness wildlife high aerial spraying effects on high profile, non-target species who makes the decisions 58

59 Pesticide classification Biological target Fungicides inorganic chemicals organometallics (mercury, arsenic, tin) chlorophenolics (pentachlorophenol) antibiotics (penicillin, streptomycin) synthetic organics (captans, carbamates) 59

60 Pesticide classification Biological target Herbicides inorganics (arsenic, cyanide) chlorophenoxy acids (2,4-D and 2,4,5-T) organophosphates dipyridals (paraquat) triazines (atrazine) 60

61 Pesticide classification Biological target Insecticides inorganics (metals) natural, plant-derived organochlorines organophosphates carbamates 61

62 Pesticide classification Biological target Acaricides Molluscicides Nematicides Rodenticides anticoagulants: coumarin (warfarin) other types 62

63 Pesticide chemical classification Inorganics Organics natural organics synthetic organics organochlorines organophosphates carbamates triazines (e.g., atrazine) glyphosates (e.g., Round-up ) 63

64 Inorganic pesticides Metal-based arsenic copper lead mercury 64

65 Natural organic pesticides Nicotine alkaloid secondary compound from tobacco early insecticide use 65

66 Natural organic pesticides Nicotine highly toxic to mammals nervous system poison causes salivation, vomiting, muscular weakness, chronic convulsions, cessation of respiration 66

67 Natural organic pesticides Pyrethrum powdered extract from chrysanthemum flowers 67

68 Natural organic pesticides Pyrethrum rapid knock-down time for insects negative temperature coefficient: body temp = effectiveness high insect : mammal toxicity ratio nervous system poison nonpersistent in environment, no bioaccumulation synthetic pyrethroids = pyrethrins 68

69 Natural organic pesticides Rotenone from tropical American woody plant cubé (genus Lonchocarpus, pea family) extract from roots used locally as a fish poison 69

70 Natural organic pesticides Strychnine extract from seeds of Strychnos nux-vomica tree very toxic to mammals used to kill rodents nerve poison, causes all muscles to contract at one time 70

71 Organochlorine pesticides Characteristics uses: insecticides, herbicides high environmental persistence resist degradation can be transported long distances in air, water year half life bioaccumulation and biomagnification easily absorbed into biological tissue acute toxicity to target species: nerve poison chronic toxicity to non-target species 71

72 Organochlorine pesticides Examples DDT lindane cyclodienes: chlordane, heptachlor, aldrin, endrin 72

73 Organophosphate pesticides Characteristics uses: insecticides, acaricides, nematicides low environmental persistence degrade easily in water or environment 1-2 month half life no bioaccumulation high acute toxicity to target and non-target species: nerve poison high chronic toxicity to humans 73

74 Organophosphate pesticides Examples parathion malathion diazinon (Spectracide) 74

75 Organophosphate insecticides Mechanism of action: inhibition of acetylcholinesterase (AChE) nerve anatomy axon dendrites soma myelin sheath nerve impulse AChE removes acetylcholine that accumulates in synapse; stops nerve impulse; protects nerve synapse 75

myelin sheath nerve impulse AChE removes acetylcholine that

76 Organophosphate insecticides Mechanism of action: inhibition of acetylcholinesterase (AChE) nerve anatomy axon dendrites soma myelin sheath nerve impulse AChE removes acetylcholine that accumulates in synapse; stops nerve impulse; protects nerve synapse 76

77 Carbamate pesticides Characteristics use: insecticides, nematicides low-moderate environmental persistence high acute toxicity to bees potential chronic toxicity to humans Example sevin (carbaryl) 77

78 Environmental impacts Risk versus benefit Most situations not well controlled application environmental transport toxicity fate and disposition persistence in environment 78

79 Case study: DDT First synthesized in : Mueller discovered insecticidal properties Nobel Prize 1948 First used in WWII controlled lice and fungus prevented typhus outbreak Wider uses through 1950s and 1960s Rachael Carson s Silent Spring Bans versus production for less developed countries 79

80 Case study: DDT Resistance of targets to DDT 51 resistant species of Anopheles 47 also resistant to dieldrin 10 also resistant to all organophosphates 4 also resistant to all carbamates 80

81 Case study: DDT Residues and biological uptake of DDT DDT remains in environment DDT DDE in biological tissue low water solubility, high lipid solubility bioaccumulation biomagnification present throughout the biosphere 81

82 Case study: DDT Effects on birds biomagnification acute toxicity following spraying acute toxicity in migrating birds eggshell thinning decrease in enzyme carbonic anyhydrase less calcium carbonate in eggshells eggs crushed during incubation decreased hatching success 82

83 DDT in a Lake Michigan food chain DDT (ppm) Bioaccumulation Water column Bottom mud ,000 Fairy shrimp Coho salmon, lake trout Herring gull Overall biomagnification: 495 million fold (water column herring gull) 7100 fold (bottom mud herring gull) 83

84 Decrease in eggshell thickness over time Eggshell thickness in sparrow hawks in Great Britain,

85 Case study: DDT Effects on birds endocrine system effects decrease in luteinizing hormone changes incubation behaviors neurophysiological effects changes in parental behavior after hatching parents neglect young 85

86 Case study: DDT Effects on fish acute toxicity to adults acute toxicity to juveniles: DDT bound to lipid of yolk sac 86

87 Case study: spruce budworms Northern temperate and boreal forests Feed on needles of mature fir and spruce in spruce-dominated forests 87

88 Case study: spruce budworms Spruce budworm population dynamics outbreaks every 35 years phases of normal outbreak endemic phase: 5 / tree outbreak phase: 2,000 / tree within 4 years epidemic phase: >20,000 / tree for 6-10 years outbreak collapse 88

89 Case study: spruce budworms 89

90 Case study: spruce budworms 90

91 Case study: spruce budworms Spruce budworm habitat preferences monospecific balsam fir or white spruce stand age >60 years host species form the canopy elevation <700 meters south of 50 N latitude New outbreaks start downwind of ongoing infestations 90% of trees can be lost within 5 years 91

92 Case study: spruce budworms Budworm damage increasing due to forest management practices clear cutting fire protection increases number of susceptible trees routine pesticide spraying old trees don t die keeps habitat intact for future outbreaks 92

93 Case study: spruce budworms History of insecticides versus budworms calcium arsenate ( ) in Nova Scotia DDT after WWII in eastern Canada damage to target and non-target species persistence of DDT in trees even when not sprayed for several years bioaccumulation in wildlife fenithrothion and biologicals also attempted 93

94 Case study: spruce budworms Effects on non-target arthropods direct toxicity disruption of predator-prey relationships removal of pollinators and detritivores Effects on birds carnivores and top carnivores particularly susceptible 94

LIVING WITH THE EARTH. THE TROUBLE WITH PESTS - Moore 1

LIVING WITH THE EARTH. THE TROUBLE WITH PESTS - Moore 1 LIVING WITH THE EARTH THE TROUBLE WITH PESTS - Moore 1 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