Pests and Diseases

1
Pests and Diseases

• 28.00 Examine distinguishing characteristics of
  pests so as to determine best management
  practices.
• 29.00 Compare methods of control of
  horticulture plant pests.

2
What is an insect?

• Small animals that have three body regions and
  three pairs of legs equaling six legs
• Body regions
• head
• thorax
• abdomen

3
Types of Insects

• The five types of mouthparts are important in
  identifying and controlling insects.
• Chewing
• Piercing
• Rasping
• Siphoning
• Sponging

4
Chewing Insects

• Insects tear, chew or grind food
• Examples
• grasshopper
• beetle

5
Piercing Insects

• Punctures plant and sucks the sap

6
Rasping insect

• Rasps or breaks surface and sucks sap
• Example
• thrips

7
Siphoning insects

• Have a coiled tube they dip into liquid food such
  as nectar and draw it in
• Example
• butterfly

8
Sponging Insects

• Have two sponge-like structures that collect
  liquid food and move it into the food canal
• Example
• housefly

9
Life Cycles

• Complete metamorphosis has four stages
• egg
• larva-worms or caterpillars
• pupa
• adult-flies, beetles, etc.

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Life Cycles

• Incomplete metamorphosis has three stages
• egg
• nymph
• adult

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Life Cycles
12
Chewing Insects

• Parts of leaves are eaten away
• beetles
• cutworms
• caterpillars
• grasshoppers

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Chewing Insects

• Beetles
• eat leaves, stems, flowers, fruit and nuts
• Cutworms
• usually attack stems, but may eat other plant
  parts

14
Chewing Insects

• Caterpillars
• larva of moths and butterflies
• fuzzy or hairy
• eat young leaves and stems
• roll up in leaves making leaves curl
• Grasshoppers
• eat all parts of plants

15
Sucking Insects

• Aphids
• Leaf bugs
• Mealy bugs
• Scale
• Thrips
• Whiteflies

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Aphids

• Pierce and suck juices
• known as plant lice
• cause stunted growth and yellow spotted leaves
• causes sticky substances and black mold
• will attract ants

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Aphids
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Leaf Bugs

• Cause plants to look unhealthy
• plants will lose their normal color and wilt

19
Leaf Bugs
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Mealy Bugs

• Pierce and suck from underside of leaves and in
  leaf axils causing yellow appearance and sticky
  secretions

21
Mealy bugs
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Scale

• Appear as black or brown raised lumps attached to
  stems and underside of leaves causing yellow
  leaves and stunted growth

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Scale
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Thrips

• Chew and then suck causing plant tissue to become
  speckled or whitened, leaf tip to wither, curl
  up, or die

25
Thrips
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Whiteflies

• Feed on underside of young leaves causing
  yellowing
• will look like flying little white specks when
  plants are shaken

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Whiteflies
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Mites

• Attack underside of leaves causing gray to
  grayish-green spots
• severe infestations cause webbing

29
Mites
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Plant Diseases
31
Diseases

• A disease is a plant disorder caused by an
  infectious pathogen or agent

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Diseases

• There are 3 conditions necessary for diseases in
  plants
• host plant
• disease causing organism or pathogen must be
  present
• favorable environment for disease organism to
  develop

33
Pathogens

• There are four groups of pathogens
• bacteria
• fungi
• viruses
• parasitic plants (attach to plants)
• mistletoe
• dodder
• lichens

34
Blight

• Causes plants to quickly turn brown or black as
  if they had been burned

35
Blight
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Canker

• Causes open wounds on woody plants

37
Canker
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Damping off

• A fungal disease that causes young plants and
  seedlings to rot off at soil level

39
Damping Off
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Gall

• Swellings or growths on plants

41
Leaf Spots

• Rings of different shades of brown, green or
  yellow that make spots on leaves

42
Mildew

• Grows on leaf surfaces--both upper and lower--as
  white, gray or purple spots

43
Mosaic

• Caused by viruses that make the leaves have
  irregular mottled areas with patterns ranging
  from dark green to light green to yellow to white

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Mosaic
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Rots

• Cause plant to decay and die

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Rust

• Causes small spots on leaves that resemble
  yellow, orange, brown or red rust mainly on the
  underneath side of leaves

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Rust
48
Smut

• A black, powdery disease that causes blisters
  that burst open releasing black spores

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Smut
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Wilt

• A disease that blocks the uptake of water in
  plant stems causing plants to wilt

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Wilt
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Controlling Pests and Diseases
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Disease Control

• Preventing plant diseases is better than treating
  the diseases
• Plant diseases must be identified before they can
  be treated

54
Environment

• Warm temperatures and moist conditions in
  greenhouse plant production make most
  horticulture plant diseases worse because of
  environmental conditions that support
  disease-causing pathogens

55
Controlling Insects

• Insects can be controlled using the following
  methods
• biological
• chemical
• cultural
• mechanical
• natural
• quarantine

56
Biological Control

• Uses natural enemies such as birds, other
  insects, etc.

57
Chemical Control

• The use of pesticides or insecticides
• Insects must be killed when they are actively
  feeding or moving on the plant

58
Chemical Control

• Contact poisons
• affect the insects nervous system and must come
  into contact with the insect to be effective
• Fumigants
• poisonous gases released into an enclosed place
  so that insects breathe the gases

59
Chemical Control

• Stomach poisons
• sprayed on the plant surfaces or are taken into
  the plant through absorption.
• The insect must suck the poison to get it into
  the stomach for this method to be effective.
• Systemic poisons are more effective for
  controlling sucking insects.

60
Cultural Control

• Involves sanitation, removing insect breeding and
  hiding areas and using insect resistant plant
  varieties

61
Mechanical Control

• Uses physical control such as insect traps, using
  screens over fans and other openings, and washing
  plants with soapy water.

62
Natural Control

• Methods include natural barriers such as rivers,
  woods, mountains and predators to control insects.

63
Quarantine

• Physically isolates insects from healthy plants

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IPM

• A combination of control methods is called
  Integrated Pest Management or integrated control.