Plant Diseases

1
Plant Diseases

• A disease is defined as any type of injurious
  abnormality
• A pathogen is any biological agent that causes an
  injurious abnormality

2
Plant diseases

• There are 4 types of commonly recognized
  pathogens
• Virus
• Bacteria
• Fungi
• nematodes

3
Signs and Symptoms

• Symptom is the plants response to attack by a
  pathogen
• Sign is structures produced by the organism (
  spore producing structures, mycelium)

4
Virus
Tobacco Mosaic Virus
5
TMV
6
TMV
7
Virus symptoms

• Unthrifty plants
• Slow to grow
• Mosaic light spots and stripes

8
Aster Yellows
Acts like a virus but is a mycoplasma
9
Virus indexing

• If you are buying cloned plants they will often
  say Virus Indexed.
• That means they are tested and proven to be virus
  free.
• very important when buying raspberry plants or
  strawberry plants

10
Bacteria- fire blight
11
Fire Blight
12
Bacterial symptoms

• Rapid spread, can be spread by wind or
  insects,humans
• Soft rots producing snotty oooz
• Can be really smelly

13
Fungi
Botrytis Grey Mold
14
Fungus
15
Fungus

• Signs mycelium, fruiting bodies
• Symptoms necrotic areas, wilt when fungus
  attacks the roots
• Phloem blockage, xylem blockage

16
Nematodes

• Root Knot Nematode

17
Nematodes

• Feed on roots and allow secondary infections
• Cause small tumors on roots

18

• Damage to plants by fungi bacteria and nematodes
  can be classified in 3 types
• Direct damage by feeding
• Toxins injected into the plant
• From secondary infections that enter via the
  physical damage caused by the primary agent

19
Crop infesting diseases are troublesome because
they will continue to reproduce and feed UNTIL

• 1. The food is used up
• 2. the environment becomes unfavorable
• 3. they are destroyed by some predator/ disease

20
Disease transmission

• Water is necessary for fungus infection
• Insects
• Humans
• Infected seed
• Infected soil brought in on shoes or tractor
  tires

21
Curing or avoiding plant disease?

• Any of the previous factors can be interrupted
• Cultural control
• Roguing, sanitation, plowing plant refuse under,
  stirring the soil to expose egg masses, keep
  plants healthy, avoid smoking, regulate pH, hot
  water treatment of seed,
• Chemical control

22
What are those letters?

• V Verticillium Wilt Virus
• F Fusarium Wilt Virus
• N Nematodes
• T, TMV, ToMV Tomato Mosaic Virus
• BSK Bacterial Speck
• ST Stemphyllium (Grey Leaf Spot)
• FCR Fusarium Crown Rot