Transcript Plant Disease

ADULT
MALE & FEMALE
LARVA AND
PUPAE STAGE
COMPLETE METAMORPHOSIS
http://www.bing.com/videos/watch/video/monarch-butterfly-pupation/4CA8292A29F610D1DA5B4CA8292A29F610D1DA5B
http://www.bing.com/videos/watch/video/monarch-butterfly-metamorphosis/242142B9588E878D68A9242142B9588E878D68A9
OTHER LARVAE/PUPAE

http://bugguide.net/index.php?q=search&keys
=caterpillars
THE DISEASE TRIANGLE
All factors present disease can result
 Methods of control can modify the triangle

Susceptible Host
Host
No
Disease
No
Disease
No
Disease
Disease
No
Disease
Pathogen
No
Disease
No
Disease
Environment
CAUSES OF PLANT DISEASES

Biotic factors (biological in origin)
 Fungi
 Bacteria
 Viruses
 Nematodes
 Phytoplasmas

Abiotic factors (non-biological)
 Weather
 Environmental
pollutants
PLANT DISEASES: FUNGI

Largest pathogen group

Over 200,000 known species of fungi
 More

than 8,000 cause plant diseases
Reproduce by asexual and sexual means
 Spores
are like seeds
SIGNS OF FUNGAL DISEASES

Powdery Mildew
 White
coating on plant
 sprinkled
 Group
 Host
with powdered sugar
of diseases
specific
 Environmental conditions
correct (high humidity)
SIGNS OF FUNGAL DISEASES

Rust
 Rusty-orange
powdery pustules
 Easily removed by rubbing leaf
 Can produce 4 types of different spores
 Alternate hosts (Cedar-apple rust fungus)
SYMPTOMS OF FUNGAL DISEASES

Symptom



Spots


Roughly circular NECROTIC (dead area)
Lesions



Abnormalities in a plant
Give us a sense if fungus or other pathogen
Irregular shaped spots
Lesions can have yellow halos
Blight

Spots or lesions enlarge and merge
Black Spot of Elm,
Gnomonia ulmea

Lesions

Often delimited
(bordered) by veins

Angular appearance

Fungal lesions more
irregular shape
Alternaria leaf blight caused by
Alternaria solani (left) and
Septoria leaf blight caused by
Septoria lycopersici (right)

Cankers
 Lesions
on stems,
branches or trunks
 Sunken
 Outer
and discolored
bark fallen away

Rots
 Destruction
and disintegration of a large
portion of the plant
 Affected areas are discolored and soft
 Crown rots
 Root rots
Southern blight
Sclerotium rolfsii

Fruit Rots
 Start
as dry rots
 Secondary microorganisms (bacteria) begin and
lead to soft, slimy rots

Pytophthora fruit rot of pumpkin

Wilts
 Indicate
plant is not
getting water
 Plants have a droopy
appearance
 Root rots
 Root
system decayed, no
longer absorb water
Cineraria with root rot
Pythium

Wilts
 Vascular
wilt invades the xylem (water
conducting tissue)
 Vascular discoloration or browning
 Xylem changes from whitish color to brown,
green or gray color
Verticillium
Bacterial Wilt
of Cucumber
carried by
Cucumber Beetle
PLANT DISEASES: BACTERIA

Second most important group of plant
pathogens
 Spots
 Lesions
 Blight
 Rots
 Vascular
 Galls
wilts

Galls

Bacterial infections can
cause galls to form

Bacterium induces gall
formation by injecting
it’s
own DNA into a plant
cell
Crown gall
PLANT DISEASES: VIRUSES

Reproduce by taking over host reproductive
machinery

Often associated with insect vectors
 Reproduction

can take place in vector
Can be transmitted mechanically
 Grower
handling issues
 Plants rubbing together
SYMPTOMS OF
VIRAL DISEASES

Mosaic

Mottling

Leaf and Fruit Distortions

Ringspot

Mosaic
 Classic
symptom
 Blotchy light and dark green coloring on leaves
 Poinsettia mosaic virus

Rose Mosaic Virus
 Interesting
lines and patterns

Mottle
 Blotchy
coloring occurs on flowers of other
colored flower parts
ECONOMIC IMPORTANCE

Some cases of viral
infections can be
highly desirable

Tulips

Leaf and Fruit Distortions



Leaves are narrow or “strappy”, thicker then normal
Leaves are curled and twisted
Fruit has warts (yellow raised bumps)
Zucchini

Ringspot
 Concentric
ring patterns on fruit or leaves
 Papaya ringspot
PLANT DISEASES: PHYTOPLASMAS

Odd bacteria like organisms

Much smaller than bacteria, need an electron
microscope

Transmitted by insects usually leafhoppers

Leafhoppers are phloem feeders
SYMPTOMS OF
PHYTOPLASMA DISEASES

Virescence

Brooming

Fasciation

Twisting and Distortion

Virescense
 Normally

colored plant parts are green
Brooming
 Plant
parts become overly branched and bushy

Brooming - Ash Yellows

Fasciation
 Flattening
Maple branch
of plant parts

Twisting, Distortion and Virescence
 Cosmos
with Aster Yellows
PLANT DISEASES: NEMATODES

Parasitic worms

Very complex compared to other pathogens

Usually seen only with a light microscope

Reproduce by eggs

Nematodes
 Identified
by extracting from soil or infected
plant material
 Non-pathogenic vs. pathogenic nematodes
 Pathogenic have a stylet
 Modified
tissue
tooth that punctures and feeds on plant

Gall formation by nematodes
 Nematode
tunnels into the root
 It’s saliva stimulates plant root cells to divide
PLANT DISEASES:
ABIOTIC FACTORS

Nutritional abnormalities

Pesticide exposure

Environmental pollutants

Adverse weather conditions
SYMPTOMS

Abnormalities are called INJURIES
 Discolortion
 Yellowing
 Chlorosis
 Reddening
TYPES OF
NUTRIENT ABNORMALITIES PAGE 169

Yellowing at margins of leaf


General yellowing


lack of nitrogen
Leaf veins remain green and leaf blades turn
yellow


lack of molybdenum
lack of iron or manganese
Reddening of foliage

lack of phosphorus

Molybdenum deficiency on poinsettia
 Yellowing
at margins

Pesticide exposure
 Curling
and cupping
 Geranium exposed to the herbicide 2,4-D

Pesticide exposure
 Twisting
 Tomatoes
exposed to the herbicide 2,4-D

Pesticide exposure
 Distortion
 Rose

exposed to a phenoxy-type herbicide
Symptoms similar to viruses and
phytoplasmas
 Gather
information

Pesticide exposure
 Fungicide
use can cause marginal burning
 Follow the label directions

Environmental Pollutants
 Contaminants
in water or the air
 Marginal bronzing on Shefflera due to exposure
to sulfur dioxide

Environmental Pollutants
 Lesions
on Dracena from high levels of fluoride
in water or fluoride gas
 Paper thin lesions, concentrated at margins

Environmental Pollutants
 Browning
of arborvitae due to dog urine

Environmental Pollutants
 Cold
injury
 Candles
 Gather
starting to grow and cold weather comes
information

Environmental Pollutants
 Heat
injury
 High
temps can cause tissue damage

Environmental Pollutants
 Adverse
 Winter
weather conditions
injury
Air temps rise but soil temps are cold
 Plant begins growing but the roots can’t get water to the
foliage
 Plant desiccates and dies


Environmental Pollutants
 Adverse
weather conditions
 Drought
stress, reddening of branches
WHERE TO GO FOR HELP…

Plant Disease Diagnostics Clinic

http://www.plantpath.wisc.edu/pddc/index.html

Soil and Plant Analysis Lab
 Nutritional

disorders
http://uwlab.soils.wisc.edu/
Slides in power point are copy write:
 1999 by the Board of Regents of the University
of Wisconsin System doing business as the
division of Cooperative Extension of the
University of Wisconsin Extension