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Diseases of Crops > Stone Fruit Diseases > Flashcards

Stone Fruit Diseases Flashcards

1
Q

Give examples of stone fruits. (7)

A

Apricot, Peach, Nectarine, Prune, Plum, Cherry, Almond

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2
Q

What Genus do stone fruits belong to?

A

Prunus

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3
Q

What is the worst stone fruit disease?

A

Sharka disease (Plum pox virus)

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4
Q

How many trees are infected by the Plum pox virus?

A

Over 100 million

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5
Q

Which fruit does the plum pox virus produce ringspot symptoms on? (Only one in the world)

A

Apricot - on the stones

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6
Q

Is premature fruit drop a symptom of plum pox virus?

A

Yes

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7
Q

Where and when was the plum pox virus first discovered?

A

Bulgaria (1915)

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8
Q

When and where was the plum pox virus first discovered in the western hemisphere?

A

Chili (1992)

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9
Q

What strain of the plum pox virus is in the USA? What year was it discovered?

A

Strain D (1999)

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10
Q

What other stone fruits does PPV-Strain D infect? (3)

A

peach, nectarine, and apricot

not cherry

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11
Q

How many years did it take to eradicate PPV-D from Pennsylvania?

A

7 years (1999-2006, with last positive recorded in 2006)

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12
Q

What is a critical component of any eradication program?

A

Extensive survey (testing samples)

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13
Q

What plant factors affect PPV-D symptoms? (4)

A

age
nutrition
status
cultivar

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14
Q

Where do symptoms of PPV appear? (4)

A

Leaves
Fruits
Flowers
Seeds

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15
Q

How are potyviruses transmitted?

A

by aphids in a non-persistent way

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16
Q

Where is the only place in the world to find PPV-D?

A

North America

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17
Q

Name two vectors of PPV.

A

Aphids

Humans

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18
Q

Is PPV seed transmissible?

A

No, or very low (single study)

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19
Q

How many species of Aphids transmit PPV? (range)

A

4-6 main

20 total

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20
Q

How many trees are tested within 1 mile of a positive PPV test?

A

All of them (8 leaves per tree)

Individual tests

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21
Q

How many trees are tested within 5 miles of a positive PPV test?

A

All of them (4 leaves per tree)

Two trees per test

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22
Q

What are the two most important control measures for PPV?

A

Early detection

Removal and destruction of infected trees

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23
Q

What is the primary host of X-disease?

A

Peaches

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24
Q

What is the secondary host of X-disease?

A

Cherry

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25
Q

List symptoms of X-disease. (4)

A

Leaves curl inward
Leaves change yellow to reddish-purple spots
Leaves fall prematurely
Fruit drops prematurely

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26
Q

What type of organism causes X-disease?

A

Phytoplasma

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27
Q

Define phytoplasma

A

Phytoplasmas are obligate bacterial parasites of plant phloem tissue and of the insect vectors that are involved in their plant-to-plant transmission.

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28
Q

How can X-disease be controlled?

A

Removal of infected trees
Insecticides against leafhoppers
Removal of secondary hosts

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29
Q

What is the vector of X-disease?

A

Leafhopper

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30
Q

What is oxytetracycline used for?

A

Trunk injection can provide temporary symptom remission of X-disease.

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31
Q

What is the causal agent of brown rot of stone fruits?

A

a Fungi

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32
Q

What is Monilinia fructicola?

What is Monilinia laxa?

A

the causal agent of brown rot of stone fruits

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33
Q

Is Monilinia fructicola in North America?

A

No

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34
Q

Is Monilinia laxa in North America?

A

Yes - California

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35
Q

What does an early infection of brown rot of stone fruits look like?

A

blossom blight or twig canker

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36
Q

What do late infections of brown rot of stone fruits look like?

A

rot of ripening fruit

37
Q

Does brown rot of stone fruits cause more damage in wet or dry years?

A

Wet

38
Q

Where does the brown rot of stone fruits pathogen overwinter?

A

mummified fruits from the previous season that remain attached to the tree or fall to the ground.

39
Q

What other infections does brown rot cause (same pathogen)?

A

blossom blight
twig blight
twig canker
fruit rot

40
Q

Where does blossom blight enter the plant?

A

through the pistil

41
Q

Does blossom blight have multiple reproductive cycles?

A

Yes

42
Q

What is a symptom of blossom blight?

A

Gummy exudates

43
Q

What do infected fruit of brown rot eventually turn into?

A

black mummies

44
Q

Do black mummies fall from the tree?

A

sometimes

45
Q

Where do main infections of brown rot originate from?

A

black mummies on the ground

46
Q

How fast can mature fruit decay from brown rot?

A

2 days

47
Q

Can brown rot remain dormant in the fruit growing season?

A

Yes - often remains inactive until fruit matures.

48
Q

Where do apothecia occur on mummified fruit?

A

only on fallen fruit (not common in nature)

49
Q

What are apothecia?

A

small mushroom like structures

50
Q

Does apothecia occur on fruit on the tree?

A

No, only on fallen fruit

51
Q

Does brown rot have secondary infections?

A

Yes

52
Q

When is the worst time for wet weather in regards to brown rot of stone fruits?

A

blossoming

53
Q

How is brown rot of stone fruits controlled?

A

fungicides
resistance to benzimidazoles
removal of mummies (cultural control)
rapid cooling after harvesting

54
Q

What is the causal agent of peach leaf curl?

A

Taphrinia deformans (a fungi)

55
Q

What is the causal agent of cherry leaf curl?

A

Taphrinia cerasi (a fungi)

56
Q

Where can you find peach and cherry leaf curl?

A

worldwide

57
Q

Where do primary infections occur in leaf curl?

A

early spring from bud swell

58
Q

Where do the most common symptoms of leaf curl occur?

A

on the leaves

59
Q

What is the underlying method that leaf curl causes the symptoms?

A

uncontrolled replication of meristematic cells

60
Q

Does leaf curl cause fruit drop?

A

Yes

61
Q

Does leaf curl infect the fruit of the tree?

A

Yes - but it is rare

62
Q

How can leaf curl be controlled?

A

fungicide in Autumn - after leaves have fallen or

in spring - before bud swell

63
Q

Does a fully mature leaf have to be protected from leaf curl?

A

No, it is naturally resistant. Leaf curl only attacks younger leaves

64
Q

When does fungicide application need to be applied in the Autumn?

A

after leaves have fallen

65
Q

When does fungicide application need to be applied in the spring?

A

before bud swell

66
Q

What stone fruits does scab appear on?

A

peaches

nectarines

67
Q

What is the causal agent of scab?

A

fungus - Cladosporium carpophilum

68
Q

Does the same agent cause scab on cherry and peaches?

A

No

69
Q

Does scab resemble cankers?

A

Yes

70
Q

When do scab symptoms occur on fruit?

A

when fruit is about half grown

71
Q

What does scab look like on fruit?

A

small greenish circular spots on fruit surface that expand over time

72
Q

Does scab lead to fruit cracking?

A

Yes

73
Q

How does scab overwinter?

A

as mycelia on twigs

as chlamydospores on the bark surface

74
Q

How can scab be controlled?

A

fungicides only

75
Q

What fungicide can be used on fruit scab?

A

calyx split (benzimydazole)

76
Q

What two bacteria are pathogenic for stone fruits?

A

Bacterial spot

Bacterial canker

77
Q

What does bacterial spot symptoms look like?

A

angular spots on the leaves along the main vain and along outer part of the leaf

78
Q

Does bacterial spot of stone fruits cause shot hole symptoms?

A

Yes

79
Q

What are the two cankers caused by bacterial spot of stone fruits?

A

Spring cankers

Summer cankers

80
Q

What bacterial spot canker occurs on past seasons growth?

A

Spring

81
Q

What bacterial spot canker occurs on this seasons growth?

A

Summer

82
Q

Where does bacterial spot overwinter?

A

infected twigs

83
Q

What does bacterial spot require for infection to occur?

A

water congestion

84
Q

What is the most effective way to control bacterial spot?

A

Avoid highly susceptible cultivars

85
Q

What bacterial cause bacterial canker?

A

Pseudomonas syringae

86
Q

What is a mark of bacterial canker on the bark of the tree?

A

gumming

87
Q

What environmental conditions favor bacterial canker?

A

prolonged periods of cold, wet weather

88
Q

Is Pseudomonas syringae resistant to copper?

A

Yes

89
Q

Is copper safe to use on stone fruits?

A

No - it damages most stone fruit trees

Diseases of Crops (11 decks)

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