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Penn State Master Gardener > Plant Diseases > Flashcards

Plant Diseases Flashcards

1
Q

What are some mobile elements in the plant?

A

Nitrogen, phosphorus, potassium, magnesium 

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2
Q

What are some Immobile elements within the plant?

A

Calcium, iron and manganese

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3
Q

If an older tissue exhibits signs of nutrient deficiency what elements are likely to be missing?

A

Mobile elements. Because those elements are transported from the older to the younger developing tissues.

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4
Q

What can cause nutrient deficiency in a plant?

A

Lack of nutrients, soil pH that makes the element unavailable, nutrient imbalance

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5
Q

What are some of the symptoms of nitrogen deficiency?

A

Yellowing of older leaves, small leaves, and stems that are short and slender.

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6
Q

What are some symptoms of phosphorus deficiency?

A

Purpleish to reddish coloration of leaves/stems, leaves may appear unusually dark green, general stunting of plants.

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7
Q

What are some symptoms of potassium deficiency?

A

Older leaves are mottled, spotted, or curled. Root systems are poorly developed.

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8
Q

What are some symptoms of magnesium deficiency?

A

Yellowing between veins of older leaves, as well as spotting of leaves.

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9
Q

What are some symptoms of iron deficiency?

A

Yellow in between veins of younger leaves, while the veins remain dark green.

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10
Q

What are the symptoms of a manganese imbalance?

A

Leaves are smaller than normal, yellow leaves are yellow between the veins, leaves, fall prematurely. Access Menganese can induce iron deficiency, therefore their share similar symptoms.

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11
Q

What are some common air pollution and other pollutants that can affect plant health?

A
  • Ethylene (caused by leaking gas pipes)
  • Fluorides (from factories, making steel, bricks and cement)
  • Ozone (from car emissions, electrical discharges)
  • Sulfur dioxide (by burning fossil fuel)
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12
Q

What are facultative parasites and under what conditions do they cause significant damage?

A
  • The type of organisms that do not have to be parasites in order to survive
  • When the plan is not vigorous because of environmental stress
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13
Q

What are some of the stages of a decline?

A

Reduction of growth, dieback, final death of a population of plans.

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14
Q

What are the main steps to a successful plant disease management?

A
  • monitoring
  • Prevention
  • Management
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15
Q

What regulatory methods exist for disease control

A

Inspection
Quarantine

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16
Q

What are some of the common cultural methods for disease control?

A
  • Closed season (grow nothing)
  • Dry fallow (till the soil so the top layer dries out)
  • crop rotation
  • Sanitation
    -Manipulating the environment (controlling humidity/soil moisture)
  • improving plant vigor
  • Planting resistant varieties
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17
Q

What does biological control of plant disease entail?

A

One organism is used to attack or at least inhibits the activity of another organism.

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18
Q

What are some of the disadvantages of biological control?

A
  • A certain level of disease must be tolerated (food source for the control agent)
  • Most control agents only work well under very specific environmental conditions
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19
Q

What is the objective of chemical controls when dealing with plant disease?

A

To eliminate or inhibit pathogen’s lifecycle.
Chemicals may kill the pathogen directly or inhibit pathogen activity or induce a resistant reaction in an otherwise susceptible plant.

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20
Q

What is the difference between contacts and systemics in chemical control?

A

Contacts are applied as sprays which requires uniform application on the plant surface and to be reapplied frequently to protect new tissues.
Systemics enter the plant and are redistributed within the plant, therefore, uniform coverage is not necessary and replication is less frequent.

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21
Q

What is the most important aspect of using chemical controls?

A

Proper diagnostics of the pathogen and knowledge of the pathogen’s biology in order to apply the appropriate material at the proper time.

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22
Q

What is phytotoxicity?

A

An unwanted effect of chemical control where the material is actually damaging the treated plant or a neighboring plant, or accumulated in the soil to a toxic level.

23
Q

How do phytotoxicity show up on different parts of the plant?

A

Poor seed germination, death of rapidly growing succulent tissues, misshapen, or distorted plants/fruits/leaves. Usually the injured tissue is sharply defined uniform in color and go entirely through the tissue.

24
Q

What are some factors causing phytotoxicity?

A
  • Chemical: crop might be sensitive; repeated application will result in accumulation of the chemical
  • Formulation: chemicals in soluble concentrates can sometimes dissolve the waxy layer on plan surfaces
  • Additives
  • Concentrations
  • Method of application: might be uneven
  • Growing conditions: temperatures during or after treatments; humidity/plant wetness
  • Growth stage
  • Mixing incompatible chemicals
25
Q

What are the casual components to disease development?

A
  • pathogen
  • Susceptible host
  • Conducive environment
  • time
    Can be multiple at the same time.
26
Q

What is the category of nonliving causes of plant diseases and what are they?

A
  • abiotic
  • Nutrients; moisture; chemicals
    Symptoms tend to be systematic can affect multiple species in the area
27
Q

What are some of the symptoms of of abiotic disease?

A
  • decline of vigor
  • Yellowing of older leaves
  • Premature leave coloration
  • Marginal leaf burn
  • Smaller than normal leaves
  • Wilt or branch dieback
  • heavier than normal seed production
28
Q

What is a pathogen’s life cycle?

A

Inoculation—infection—incubation—invasion—reproduction—dispersal—dormancy —…

29
Q

What are some biotic disease causes?

A

Bacteria; fungi; nematodes; phytoplasmas; vascular plants; viroids; viruses

30
Q

What are fungi’s food sources?

A
  • living tissues of other organisms
  • dead organic matter
31
Q

What are obligate parasites?

A

Can only survive by living off of specific live organisms.

32
Q

What is the fruiting body?

A

The visible/above ground part of the mycelium.

33
Q

What is the difference between disease symptom and sign?

A

Symptom: the appearance of the plant
Sign: the visible pathogen

34
Q

What are some entry point of bacteria into the plant?

A
  • natural openings e.g. stomata; hydathodes; lenticels; nectaries
  • wounds made by insect feeding
  • mechanical injuries
  • pruning/grafting
35
Q

What are fire blight control methods?

A

Prune during dormancy
Plant resistant species

36
Q

What is an overgrown tissue on a tree called?

A

Gall

37
Q

What are nematodes?

A

No segmented roundworms that have rudimentary nervous system, no heart or lungs.

38
Q

What are the categories of nematodes based on lifestyle?

A
  • migratory ectoparasites: move around and stay outside the plant
  • migratory endoparasites: enter and move inside its tissues
  • sedentary ectoparasites: stop moving and stay in place outside the plant
  • sedentary endoparasites: stop moving and stay in one place inside the plant once established
39
Q

What are phytoplasmas?

A

Similar to bacteria but without cell wall. Can be transmitted by insect (leafhoppers).

40
Q

What are bacteria?

A

Single cells surrounded by a cell wall, lacks nucleus.

41
Q

What are the plants that parasitism other plants called?

A

Vascular plants
Eg: dodder; mistletoe

42
Q

How is a viroid different from a virus?

A

Viruses are pieces of genetic materials (RNA or DNA) surrounded by protein coat and can be spread by several ways.
Viroids have no protein coat and can be spread through vegetative propagation.

43
Q

How can viruses spread from plant to plant?

A
  • vegetative propagation
  • grafting
  • vascular plants e.g. fodder sends vines from one plant to another
  • animals (big and small - eg: aphids, leafhoppers)
  • seeds
  • pollen
  • certain root-infecting fungi
44
Q

What are some symptoms of diseases appearing/affecting leaves?

A
  • anthracnose: dead areas, concentric lines (pimple-like)
  • blight: rapid killing of leaves/branches (can be caused by bacteria or fungi)
  • scorch: dead areas between the veins or along the margin
  • leaf spots: small or large areas of damaged tissue
45
Q

What are cankers?

A

Localized areas of dead bark and underlying wood on twigs, large branches and trunks.

46
Q

What causes canker?

A
  • living organisms e.g. fungi, bacteria
  • environmental factors e.g. excessive low/high temps, hail
47
Q

What are the three types of canker?

A
  • annual: cause by fungi; only stressed out trees get them but can turn permanent if conditions persist
    e.g. fusarium
  • perennial: rarely lethal, weaken its structure
    e.g. nectria, eutypella
  • diffuse: invades rapidly, can kill host plant in one season
    E.g. chestnut blight
48
Q

What is and what causes damping off?

A

Rotting or seeds in the soil and destruction of newly emerged seedlings.
E.g. Pythium fungi, fusarium fungi

49
Q

What condition promote damping off?

A

Excessive soil moisture; excessive misting; low soil temp before germination, high soil temp after emergence.

50
Q

What are some preventive measure to manage damping off?

A

start seeds in pasteurized soil or soilless mix; use sterile pots/flats; sanitize tools; buy fungicide-treated seeds.

51
Q

What causes damping off?

A

Fungi; insect; bacteria etc
Most notably: agribacterium tumefaciens

52
Q

What are symptoms of root rot?

A
  • bases of cutting are brown/black
  • plants are stunted
  • root tips are brown/dead
  • brown tissue or the root peels off
  • root cells contain spores
  • stems rot at soil line
53
Q

What is a heteroecious fungi?

A

Fungi requiring two separate species of host plant to be present to be able to complete its life cycle.
E.g rusts
Opposite: autoecious

54
Q

What are some rust types and what are the most commonly occurring rusts in the USA?

A
  • leaf ~; gall~; canker~
  • Bean; cedar-apple; cedar-quince

Penn State Master Gardener (3 decks)

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