1. Fungi as Disease Organisms
Plant Pathology
Fungi as Disease Organisms

2. Slime Moulds Most not pathogenic to plants
highly conspicuous fungi that often seem to "magically" appear on mulch, plants, and turf overnight
the rapid appearance of these nuisance fungi is frequently a cause for misdirected alarm.

3. Clubroot of Crucifers (Cabbage, cauliflower)
Widely distributed around world
Can cause severe damage
Pathogen remains in soil indefinitely
Plasmodiophora brassicae

5. Oomycete Diseases Soil pathogens Aboveground
Roots, lower stems, tubers, seeds, fleshy fruits lying on soil
Aphanomyces, Pythium, Phytophthora
Aboveground
Leaves, young stems, fruits
Phytophthora, Pythium,

6. Diseases
Downy mildews
White rust
Pythium
Damping off
Root rots

11. Sudden Oak Death
Ramourm blight

14. Olpidium
Parasitic on algae, fungi, mosses, pollen grains, flowering plants
Zoosporangium
Resting sporangia

16. Zygomycetes Rhizopus Mucor Weak parasites
Soft rot of fruits and vegetables
Mucor
Soft rot
Weak parasites
Mostly grow on dead or processed plant products

17. Rhizopus Rot

20. Diseases Caused by Ascomycetes
Leaf and fruit spots / blights
Fruit decay and rots
Vascular wilts
Root and stem rots
Stem and trunk cankers

21. Powdery Mildews Attack many hosts
White to grayish patches on plant tissues
Chlorosis, tissue distortions, necrosis
Obligate parasite
Causes yield reductions

24. Apple Scab Very important disease Scabby lesions on leaves and fruit
Fruit stunting, and drop, defoliation
Requires cool springs and summers

28. Basidiomycetes Smuts and Rusts
Smuts and Bunts (Ustilaginales)
Ustilago, Tilletia
Rusts (Urediniales)
Puccinia, Uromyces
Rots of roots, crowns, and stems
Armillaria, Rhizoctonia, Scloerotium

31. Smut Diseases Important cereal diseases Smuts (Ustilago spp.)
Barley, wheat, oats, corn
Smuts (Ustilago spp.)
Bunts (Tilletia spp.)
Causes reduced yields, quality

32. Smut Diseases Monocyclic diseases Systemic growth
Corn smut – Ustilago maydis
Loose smut – U. tritici (wheat)
- U. nuda (barley)
- U. avenae (oats)
Common bunt – Tilletia spp (wheat)
Karnal bunt – T. indica (wheat)

39. Basidiomycete Rots Rhizoctonia Sclerotium Armillaria Wood Rots
White and brown
“Mycelia Sterilia”

42. Control Quarantines and Inspection Pathogen Free Propagating material
Host eradication
Crop rotation
Sanitation
Vector control
Biological control agents
Chemicals
Foliage sprays
Seed treatment
Soil treatment

43. Site / mode of action Comments Nucleic acid synthesis
Some that control Oomycetes
Microtubules
A few systemics
Protein synthesis
A few
Lipids and membranes
Affect phospholipids or biosynthesis or membranes
Sterol biosynthesis
Many important fungicides affect sterol pathways
Melanin synthesis
Various, unknown

44. Some Examples Ridomil – specific for Oomycetes
Score – systemic for almost any crop against wide range
Tilt – rusts and leaf spot
Unix – for some difficult to control pathogens