page 97

PEST AND PEST CONTROL 

Pest- any undesirable organism that is injurious to plants, either directly (ex. insects, or fungi)
          or indirectly (ex. weeds). 

THREE PREREQUISITES OF PEST DAMAGE OR INFECTION
1) plant  susceptible
2) pest present
3) proper environment

PEST DAMAGE CONTROL
1) Plant Resistance
   a) Genetic Resistance - this is the "ideal" method of pest damage control 
2)
Proper Environment
   a) Favorable for plant 
   b) Unfavorable for pest
3) Eliminate Pest

    a)Quarantine - usually governmentally imposed 
    b) Sanitation - wash pots and tools, hoses off ground, propagate clean plants, etc. 
    c) Physical Control - bug traps, screens, sticky boards, etc. 
    d) Biological Control - the use of one organism to control another organism. 
        1) Bacillus thuringiensis - a bacterium that controls caterpillars 
        2) grass carp (or white amour) - a fish that eats submerged aquatic weeds 
        3) predaceous mites - eat other mites and small insects 
        4) parasitic wasps - lay eggs inside other insects 
        5) Trichoderma - a fungus that controls other fungi 
        6) allelopathy - secretion of chemicals by one plant that retards the growth of surrounding plants 
    e) Pesticides- chemicals used to control pests; ex. fungicide, bactericide, insecticide, miticide,
                           herbicide. 
        Modes of Action 
        1) Contact Pesticide (insects and weeds) 
        2) Systemic Pesticide (insects and weeds) 
        3) Stomach Poison (insects only) 

Integrated Pest Management (IPM) - the use of all strategies of pest damage control (resistance, cultural, biological, environmental and chemical) to minimize the economic impact of pests.


page 98

TYPES OF PESTS - INSECTS

INSECTS

    Class Insecta
    Characterized by:

  • 6 legs
  • 3 body regions; head, thorax, abdomen
  • 1 pair antenna
  • wings (may be reduced or vestigial)

      Order Hemiptera - very common insect pests on horticultural crops
      Characterized by:

    • sucking mouth parts that extract phloem sap
    • secretion of  honey dew - a sugary liquid secreted by Homoptera
    • presence of  sooty mold - a black to brown mold that grows on honey dew on the leaf surface
      does not infect plant)
    • includes aphids, mealybugs, scale and whitefly listed below

1) aphid - sucking mouth parts; small soft bodies, green, brown or black; 
                around growing point; ants may "farm".

2) mealybug - sucking mouth parts; soft bodies covered with cottony wax
                       filaments

3) scale- sucking mouth parts; covered by a hard shell

4) whitefly - immature with sucking mouth parts; as translucent ovals under the leaf; 
                    adults as small white flies

5) thrips- rasping-sucking mouth parts; cause lesions on young leaves and 
                flower petals 

6) leaf miner - bore meandering tunnels through leaves 

7) caterpillar - have chewing mouth parts and eat whole tissues; leave droppings

8) grub and borer - larva of beetles; feed on roots, bore into wood of stems 

9) beetle - have chewing mouth parts and eat whole tissues 

10) grasshopper - have chewing mouth parts and eat whole tissues 

11) weevil - feed mainly on stored grain. 


page 99

TYPES OF PESTS - ARACHNIDS, NEMATODES AND MOLLUSKS

MITES

    Class Arachnida (mites, spiders, ticks, scorpions)
    Characterized by:

  • 8 legs
  • 2 body regions; cephalothorax, abdomen 
  • no antenna or wings 

1) spider mite, red spider or spotted mite - very small; cause a fine yellow 
    speckling on leaves where they feed, and form webs when severe 

 
NEMATODES - eel or wire worms (extremely small)

1) root-knot nematode -  bore into roots and cause the root to have a swollen, 
    knotted appearance.
 
MOLLUSK

1) snails - with shells; chew on young plant parts, soft tissue; leave slime trails

2) slugs - without shells; chew on young plant parts, soft tissue; leave slime trails.

page 100

TYPES OF PESTS - DISEASES CAUSING PESTS AND WEEDS

DISEASE-CAUSING PESTS
pathogens - microorganisms that invade, infect and cause damage to another living organism.
 
Type Microorganism

Appearance/Symptoms on Plant
1) fungi
long, multicellular filamentous microorganisms composed of membrane-bounded cells surrounded by  cell walls
  • moldy or powdery appearance on leaf
  • causes necrotic spots
2) bacteria
usually rod shaped, single-celled (may form filaments) microorganisms composed of a membrane-bounded cell surrounded by a  cell wall.
  • causes soft, mushy, odorous regions on leaves or stems, "soft rot"
  • causes circular, ringed lesions
3) virus
rod-shaped, spherical or crystalline-shaped microorganisms  composed of strands of nucleic acids surrounded by a protein coat.
  • causes yellow mosaic or mottling of leaves
4) mycoplasma  and spiroplasma
pleomorphic (means takes on shape of the organism it is in) microorganisms with membrane-bounded cells, but without cell  walls.

5) rickettsia-like organisms
bacteria-like organisms that can only live inside living cells

 WEEDS - any plant out of place.
    Cause Damage by: 
    1) competition
    2) allelopathy 
    3) expense
    4) disease and insect hosts
    5) contaminate foods
    6) poisonous
    7) aesthetically undesirable
    8) parasite, ex. dodder, mistletoe


Go to:  Table of Contents | Introduction | Anatomy | Physiology | Hormones | Temperature |
|
Light | Water | Soil | Nutrition | Propagation | Pruning | Pests |
Page: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100