Plant Pathology Exam 2 Mogen

Front 1

Dutch Elm Disease (DED):
the perfect stage scientific name?

Back 1

Ophiostoma ulmi
ophi= snake, stom= openning...larvae make snake-like pathways/openings

Front 2

what are synnemata?

Back 2

Collection of conidiophores fused together to form a stalk, with conidia at the end or on the edges.
(aka coremium)

(**found in DED)

Front 3

vector for Dutch Elm Disease?

Back 3

American and European elm bark beetle

Front 4

obligate or non-obligate parasite:
dutch elm disease?

Back 4

obligate
(can only grow on elms, not artificial media)

Front 5

Dutch elm Disease disrupts the _____ system of elms, therefor it is a _____ disease.

Back 5

vascular system

wilt

Front 6

What is the biggest difference between the American and European elm bark beetles relating to disease?

Back 6

• Native/American; female cuts egg galleries PERPENDICULAR to wood grain
• European (smaller and most common); female cuts egg galleries PARALLEL to the wood grain (larvae tunnel across the grain)

Front 7

Elms defense mechanisms kill it in the end...what are these defenses?

Back 7

Tyloses and gums plug vessel element

Front 8

What are tyloses?

Back 8

Tyloses occur when a parenchyma cell protoplasm extends into a xylem or tracheid element. It is assumed they contribute to blockage of the vessels and inhibit water flow thus enhancing the wilt process. (Commonly found in many wilt diseases)

Front 9

Other than the beetle vector, how can Dutch Elm Disease spread?

Back 9

Root grafts (cephalosporium conidia in vessels pass through roots),
firewood transport

Front 10

Dutch Elm Disease:
homothallic or heterothallic?

Back 10

heterothallic (requires compatible mating types)

Front 11

What DED symptoms are shown on the underside of bark?

Back 11

Vascular streaking
(brownish blueish streaking)

Front 12

What is the most effective way to control Dutch Elm Disease?

Back 12

Sanitation
1. remove dead elms ASAP
2. Store wood barkless
3. Prune flagged sites of trees

Front 13

What are 2 controls of DED other than sanitation?

Back 13

resistance
fungicide injections (expensive- only used on valuable trees)

Front 14

What is an autoclave?

Back 14

an instrument to sterilize equipment and supplies by subjecting them to high pressure saturated steam at 121 °C for around 15–20 minutes depending on the size of the load and the contents

Front 15

what are the components of growth media?

Back 15

1. energy source (eg glucose)
2. Amino acids (eg peptone)
3. Vitamins & minerals
4. Agar (holds everything)
5. low pH (inhibits bacterial contamination)

Front 16

5 types of growth media?

Back 16

complex (most common)
synthetic [aka defined culture (specific)]
semi-synthetic
differential (pectic agar)
selective

Front 17

Common contaminants: which one looks like a pom pom?

Back 17

Aspergillus sp.
molds; ascomycetes

Front 18

Common contaminants: which is characterized by columella (looks like a mallet covered with spores)?

Back 18

Rhizopus stolonifer
black bread mold; a zygomeyete

Front 19

Common contaminants: characterized by branching growth form?

Back 19

Penicillium sp.
molds; ascomycetes

Front 20

scientific name for Oak Wilt?

Back 20

Ceratocystis fagacearu
(Cerat= horn, so horn cyst of oak)

Front 21

which oaks are most susceptible to oak wilt?

Back 21

Red oaks
(a few weeks, compared to years for white oaks)

Front 22

Oak wilt vector?

Back 22

Nitidulid (picnic/sap) beetle

Front 23

Oak wilt is native to ______.

Back 23

the US.

Front 24

Describe some symptoms of oak wilt.

Back 24

Leaf discoloration
Vascular discoloration/tyloses
Pressure pads/cracks (with sweet banana smelling spores!)

July-August

Front 25

Where are you likely to find oak wilt?

Back 25

"infection centers" radiating from nearby tree via grafting

Front 26

Scientific name for oak wilt

Back 26

Ceratocystis fagacearu

Front 27

plating infected oak wilt material reveals....?

Back 27

-Dark mycelium
-Boxy, hyaline (crystal-like) endo-conidia produced in chains
-Unique fruity odor
-Pathogen is heterothallic [Perithecia on pads if both mating types present (uncommon though)]

Front 28

Oak wilt- homothallic or heterothallic?

Back 28

Pathogen is heterothallic—presence of
perithecia on pads if both mating types are
present (not common)

Front 29

Main cause of oak wilt spread?

Back 29

root graft

Front 30

2 best controls for Oak wilt?

Back 30

1. Avoid wounding, pruning trees in early spring when most susceptible
2. Sanitation
a. Removal of diseased trees ASAP
b. Trenching to disrupt root grafts (Trench 54 inches or deeper to disrupt root graft)

Front 31

Scientific name for Chestnut blight?

Back 31

Cryphonectria parasitica
(memory: chestnut death makes you cry)

Front 32

chestnut blight originates from _____?

Back 32

Japan
(brought to NY in late 1800's)

Front 33

Industries impacted by Chestnut blight?

Back 33

Tanning industry
Lumber
Nuts (incredible disruption of lives)

Front 34

Where did chestnut blight have the greatest impact?

Back 34

Appalachia, where 25% of trees were chestnuts - lost 3-4 billion trees!

Front 35

Which disease is characterized by cankers?

Back 35

Chestnut blight

(these can girdle a tree)

Front 36

Which disease is characterized by pressure pads?

Back 36

Oak wilt

Front 37

How is chestnut blight spread?

Back 37

Infects bark through wound sites, spreads locally to produce a perennial canker,
*Edges of cankers are covered with asexual vase shaped pycnidia (with lots of conidia in a sweet nectar!)which are spread by flying/climbing insects, and wind born ascospores from sexual perithecia .
(pathogen parasitizes many species but has greatest impacts on chestnuts)

Front 38

Is chestnut blight homothallic or heterothallic?

Back 38

homothallic (only tree disease covered that does not need compatible mating type)

Front 39

Which tree disease is a faculatative saprophyte?

Back 39

chestnut blight (Cryphonectria parasitica)

Front 40

What is the best control for Chestnut blight?

Back 40

none are very good. ;(
-Fungicides are unrealistic for natural stands
-No resistance in American Chestnu
**Biological Control; best chance?
hypovirulence?

Front 41

1. What is hypovirulence?

2. To what disease is hypovirulence relevant?

Back 41

1. viral pathogens that weaken the fungus

Double-stranded RNA passed from hypovirulent strains to wild-type via anastomosis (hyphal fusions)
– Drill small holes at edge of canker and inoculate with a compatible HV strain—cover hole with tape
• The dsRNA appears to be from a mycovirus that promotes attenuation…
– Grow slower
– Produce fewer spores
– Allows the tree to “outgrow” the canker

2. May be our last, best hope for saving American
chestnut!

Front 42

What is a concern with the use of hypovirulence in chestnut blight?

Back 42

Genetic variability in the fungus may cause severe problems for the long-term usefulness of technique

Front 43

What 2 lessons did we learn from
Chestnut Blight?

Back 43

*Perennial-tissue diseases are long-lived and their spread can be very slow, but steady and hard to stop
*Pathogens that appear minor in their native habitats can become very severe when exposed to a new environmen

Front 44

Scientific name for Ergot?

Back 44

Claviceps purpure

Front 45

What is a stroma and what disease does it characterized?

Back 45

a mass of perithecia (with asci) embedded in a head, supported by a stalk arising from a sclerotium.
Ergot, (and also fusarium head blight, although without the stalk)
(don't confuse with synnemata (conidia head) of DED)

Front 46

what is a sclerotium and what disease does it characterize?

Back 46

a compact overwintering mass of hardened fungal mycelium containing food reserves which gives rise to stromata.
Ergot
*These are the elements that almost resemble a grain and which are poisonous.

Front 47

symptoms of Ergotism in humans?

Back 47

”St. Anthonyʼs Fire”
• Alkaloids cause Vasoconstriction which leadsto gangrene

* But has medicinal use too: Used to treat bleeding during childbirth

Front 48

What medicinal use does ergot have?

Back 48

Used to treat bleeding
during childbirth

Front 49

Best control for Ergot?

Back 49

informed practices such as:
Clean seed
Deep plowing to bury sclerotia (no till not an option)
Mow wild grasses (which harbor ergot)
Crop rotation

(Plants are more susceptible if flowers stay
open longer, e.g. male-sterile barley)

Also Fungicides, but only if cost-effective

Front 50

What is the scientific name for apple scab?

Back 50

Venturia inaequali
(memory...johnny appleseed's venture)

Front 51

What is the range of hosts for apple scab?

Back 51

All major apple varieties susceptible
All Malus species susceptible (wild, crab, or orchard apples)

Front 52

How does apple scab affect the apple industry?

Back 52

lowers fruit quality
can lose a whole crop
most trees heavily sprayed

Front 53

Best control for apple scab?

Back 53

MUST spray before, during, or after a rain until all ascospores are discharged
Protectant fungicides will reduce primary infection and lower later spray costs, but still need to monitor throughout season.
*also remove infected leaves
**More organic fungicides are applied per acre to apples than to any other major crop!

Front 54

What is a biocontrol for apple scab?

Back 54

antagonistic fungi sprayed
on leaves on ground to suppress
ascospore production—still in infancy. (Spraying still works best so far)

Front 55

What the biological monitoring program for apple scab?

Back 55

Apple Scab Computer software:
•Monitors weather data, temp, rainfall, humidity, & predict using models

Front 56

Scientific name for powdery mildew?

Back 56

Oidium (asexual) or Spharotheo monilioides

(mildew sounds a bit like moniloides)

Front 57

Worst pathogen in terms of economic losses?

Back 57

Powdery mildews
(nickel & dime, highest yield losses)

Front 58

Bordeaux mixture:
Who discovered it?
What was the crop/country where it was discovered?
Where did the new disease originate that caused it’s discovery?

Back 58

botany professor Pierre-Marie-Alexis Millardet discovered.
Discovered in Bordeaux, France on grapes.
Originated in America.

Front 59

control for powdery mildew?

Back 59

Young tissue generally most susceptible
(common—referred to as “adult plant
resistance”)—PROTECT EARLY

Fungicides/sulfur applications
Cultural; control humidity (in greenhouses)

Front 60

How does powdery mildew affect plants?

Back 60

The lower leaves are the most affected, but can spread up and down plant.
Can stunt plant or reduce kernel size.

Front 61

hypersensitive flex reaction

Back 61

a defense necrosis, (like tyloses) surrounds pathogen with dead cells to prevent spread of disease

Front 62

are powdery mildews obligate or non-obligate parasites?

Back 62

obligate, races differ by host species
(use haustoria)

Front 63

What is the gene for gene hypothesis?

Back 63

for every resistance gene, a gene for virulence exists

Front 64

When do you see oak wilt and powdery mildew symptoms?

Back 64

late summer/fall

Front 65

When do you see DED symptoms?

Back 65

early summer

Front 66

what are the optimal climate conditions for powdery mildews?

Back 66

high humidyity and warmth, but NOT free moisture

Front 67

Of the ascomycete tree diseases, which are homothallic and which are heterothallic? (Oaks, chestnuts, elms)

Back 67

Hetero: dutch elm disease and oak wilt

homo: chestnut blight

Front 68

which deuteromycete from lab is a local tomato disease?

Back 68

Septoria (leaf spot)
septoria also affects wheat (video-septoria leaf blotch)

Front 69

Which contaminant from lab can cause liver cancer?

Back 69

Aspergillus flavus (pom pom)

Front 70

Which are the most important pathogens involved in "damping off"? Give brief description of appearance under scope.

Back 70

Rhizoctonia (characterized by right angle branching, with constriction at base of branch)
and
Pythium (with aseptate hyphae)

Front 71

what is damping off?

Back 71

killing of seedling before or just after germination

Front 72

name of the homothallic ascomycte model organism for genetic studies?

Back 72

Sordaria

Front 73

epidemiology in plant pathology is...?

Back 73

the study of plant
epiphytotics

Front 74

What do plant epidemiologists evaluate?

Back 74

Disease INCIDENCE and SEVERITY and YIELD LOSS

Front 75

what is disease incidence in the field of plant epidemiology?

Back 75

• The number or percentage of plants infected
( Often no correlation between disease incidence and
either disease severity or yield loss)

Front 76

what is disease severity in the field of plant epidemiology?

Back 76

Percentage of the total plant tissue area infected

Front 77

define yield loss in plant epidemiology.

Back 77

Amount of crop not harvested directly attributable to
the disease, i.e. the difference between attainable yield
and actual yield

Front 78

The amount of disease where control costs just equal
incremental crop returns is called...?

Back 78

– “economic threshold”
– extremely variable and depends on crop, pesticide, and other costs

Front 79

What disease causes cankers in plum and cherry?

Back 79

black knot

Front 80

The SHAPE of a disease progress curve gives clues to the type of disease you are dealing with...
What kind of disease has an s-shaped "sigmoidal" curve and how are these diseases controlled?

Back 80

Polyetic/polycyclic diseases

Control is geared toward reducing or delaying the total number of infection cycles or initial primary inoculum and the rate of infection, (moving the "s" to the right, can't complete life cycle)

Front 81

The SHAPE of a disease progress curve gives clues to the type of disease you are dealing with...
What kind of disease has an "saturation type" sloping off curve and how are these diseases controlled

Back 81

Monocyclic Diseases; No Repeating Stage

*Control these diseases by controlling the initial inoculum since initial inoculum is proportional to the final amount of disease

Front 82

What is the range for disease rates (amount of disease increase per unit of time)?

Back 82

from r = 0.5 per day ( i.e. disease increased
50% per day) for some virulent polycyclics, to…
• 0.02 per year for some polyetics

Front 83

The calculated area underneath a disease progress curve represents....?

Back 83

Total amount of disease

Front 84

AUDPC means?

Back 84

Area Under the Disease Progress
Curve:
• Used to compare epidemics

Front 85

What are Epidemic “rates”, how are they calculated and how and what is their application?

Back 85

-Rate = “r” = the amount of disease increase
per unit of time
-They are calculated from disease progress curves
-Allows scientists to compare relative virulence and resistance and create predictive models!!

Front 86

what are the names for the predictive model programs for late blight and apple scab?

Back 86

"apple scab" and "blightcast"

Front 87

Describe how predictive models help predict conditions for Stewarts Wilt.

Back 87

Erwinia stewartii overwinters inside the
bodies of its vector, the corn flea beetle
Flea beetles are killed by prolonged cold
weather
Initial inoculum can be estimated by taking the sum of the mean temperatures for Dec., Jan., and Feb.
When the sum is <-1°C, most vectors are killed and there is little disease

Front 88

What is a symptom of Fusarium head blight?

Back 88

white tops of wheat, bleached after ascospores penetrate anthers and proliferate downward through the rachis

Front 89

What is a sporodochium?

Back 89

a small, compact stroma that bears the conidiophores (which bear conidia)
*Fusarium head blight is characterized by these.

Front 90

Chlamydospores?

Back 90

a thick-walled asexual spore which survives in unfavorable conditions
*Characteristic of Fusarium head blight

Front 91

How big are prokaryotes?
How many species estimated?

Back 91

1–5 microns; about
25,000 “species”

Front 92

important characteristics of prokaryotes?

Back 92

no organelles
rapid growth rates
reproduce by binary fission
single “chromosome” (nucleoid)
often contain plasmids

Front 93

what are plasmids?

Back 93

• extrachromosomal pieces of DNA

Front 94

Plant pathogenic bacteria: can they grow easily on artificial media? How do they obtain nutrients?

Back 94

most plant pathogenic bacteria are
“saprophytes” and can be grown on
artificial media

Front 95

How do bacteria get around?

Back 95

Vectors

many are motile by means of flagella,
although this is not significant for longdistance spread

Front 96

What are the 2 main groups that plant path bacteria are broken down into?

Back 96

Gram positives which stain purple (P&P)
(the gram stain that differentiates based on cell
wall differences)
Gram negatives that stain red (red light)

Front 97

2 types of flagella?

Back 97

• flagella can be polar (located on one end)
• or, peritrichous (all around the cell)

Front 98

Provide a description of the following bacteria shapes:
cocci
bacilli
spirilli
pleomorphic

Back 98

cocci = spherical
bacilli = rod-shaped
spirilli = coiled or spiral shaped
pleomorphic = variable; often “comma” or
“y” shape

Front 99

entry points for bacteria to passively infect a plant.?

Back 99

wounds
stomates
hydathodes (tips of leaves; guttation)
lenticels on bark and stems
nectaries on blossom

Front 100

How are plant path bacteria spread?

Back 100

Rainsplash the most common shortdistance mechanism
Vectors…
insects
contaminated seed or plant debris
human

Front 101

soil inveders vs. soil inhabitants

Back 101

Most bacteria are “soil invaders”; they can live in the soil or “rhizosphere”
for relatively short periods of time
Many plant pathogenic bacteria are “soil inhabitants”; grow and increase their populations in soil

Front 102

“forma specialis" for bacteria?

Back 102

pathovar...
a sub-species designation that permits us to differentiate isolates that are identical in every respect except VIRULENCE PATTERN

Front 103

Symptoms caused by
bacteria?

Back 103

Virtually all…
leaf spots
vascular wilts
overgrowths
cankers
galls
soft rots
scabs, blights, et

Front 104

signs of bacterial infection in plant?

Back 104

very few; bacterial ooze, bacterial streaming

Front 105

bacteria that form galls?

Back 105

Agrobacterium s

Front 106

bacteria:
the major “soft-rotters"

Back 106

Erwinia sp.
(Memory: somebody named Erwin is soft)

Front 107

which "bacteria" produce the earthy smell of soil?

Back 107

Streptomyces sp

Front 108

Bacteria genus that is often very slow growing, pleomorphic bacteria.
example from Genus:bacterial ring rot of potato

Back 108

Clavibacter sp

(memory: pleomorphic can be in the shape of a clavicle, clavicles are slow growing)

Front 109

Bacteria Genus that is broken down into two sub groups based on fluorescence on “King’s B” growth media; fluorescent and non-fluorescence.
Often human pathogens too.

Back 109

Pseudomonas sp
(memory: falsely(pseudo) singular (mon), because under king b's media, we see there are actually 2 sub groups!!)

Front 110

Bacteria Genus AKA the "fastidious vascular bacteria" or RLO’s (Rickettsia-like organism)

Back 110

Xylella sp

Front 111

What are
Phytoplasmas?

Back 111

bacterial relatives
formerly the “mycoplasma-like organisms”
= MLO’s
smallest known living cells; no cell wall
obligate parasites; increase in Vinca
restricted to sieve cells of plants
usually have a leafhopper vector in which they can multiply
Witches’ brooms a common symptom

Front 112

What are spiroplasmas?

Back 112

Spiroplasmas are like phytos but are
helical and can be grown in culture to
produce characteristic “fried-egg” like
colonies
citrus stubborn and corn stunt are the only
two major diseases know

Front 113

All plant pathogenic nematodes are ______ _______ and have a ____mouthpart.

Back 113

obligate parasites
stylet

Front 114

soybean cyst scientific name?

Back 114

Heterodera glycines

(introduced pest)

Front 115

a nematode that is one of the top 5 plant pathogens and a huge problem in warmer climates?

Back 115

Root knot nematode;
Mebidogyne sp.

Front 116

significance of Arthrobotrys conoides?

Back 116

a biological control for nematode pests
fungal rings "lasso" nematodes and kills 'em.

Front 117

nematode sampling for migratory vs sedentary parasites?

Back 117

migratory: pie pan filtering
sedentary: flotation method

Front 118

polyetic

Back 118

occuring for more than 1 year
like perennial

Front 119

When does septoria leaf blotch result in significant yield loss?

Back 119

when the infection reaches the top three leaves of the wheat plant. (starts on bottom leaves)