Stone Fruit Diseases

Question 1

Give examples of stone fruits. (7)

Answer 1

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

Question 2

What Genus do stone fruits belong to?

Answer 2

Prunus

Question 3

What is the worst stone fruit disease?

Answer 3

Sharka disease (Plum pox virus)

Question 4

How many trees are infected by the Plum pox virus?

Answer 4

Over 100 million

Question 5

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

Answer 5

Apricot - on the stones

Question 6

Is premature fruit drop a symptom of plum pox virus?

Answer 6

Yes

Question 7

Where and when was the plum pox virus first discovered?

Answer 7

Bulgaria (1915)

Question 8

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

Answer 8

Chili (1992)

Question 9

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

Answer 9

Strain D (1999)

Question 10

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

Answer 10

peach, nectarine, and apricot

not cherry

Question 11

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

Answer 11

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

Question 12

What is a critical component of any eradication program?

Answer 12

Extensive survey (testing samples)

Question 13

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

Answer 13

age
nutrition
status
cultivar

Question 14

Where do symptoms of PPV appear? (4)

Answer 14

Leaves
Fruits
Flowers
Seeds

Question 15

How are potyviruses transmitted?

Answer 15

by aphids in a non-persistent way

Question 16

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

Answer 16

North America

Question 17

Name two vectors of PPV.

Answer 17

Aphids

Humans

Question 18

Is PPV seed transmissible?

Answer 18

No, or very low (single study)

Question 19

How many species of Aphids transmit PPV? (range)

Answer 19

4-6 main

20 total

Question 20

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

Answer 20

All of them (8 leaves per tree)

Individual tests

Question 21

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

Answer 21

All of them (4 leaves per tree)

Two trees per test

Question 22

What are the two most important control measures for PPV?

Answer 22

Early detection

Removal and destruction of infected trees

Question 23

What is the primary host of X-disease?

Answer 23

Peaches

Question 24

What is the secondary host of X-disease?

Answer 24

Cherry

Question 25

List symptoms of X-disease. (4)

Answer 25

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

Question 26

What type of organism causes X-disease?

Answer 26

Phytoplasma

Question 27

Define phytoplasma

Answer 27

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

Question 28

How can X-disease be controlled?

Answer 28

Removal of infected trees Insecticides against leafhoppers Removal of secondary hosts

Question 29

What is the vector of X-disease?

Answer 29

Leafhopper

Question 30

What is oxytetracycline used for?

Answer 30

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

Question 31

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

Answer 31

a Fungi

Question 32

What is Monilinia fructicola? | What is Monilinia laxa?

Answer 32

the causal agent of brown rot of stone fruits

Question 33

Is Monilinia fructicola in North America?

Answer 33

No

Question 34

Is Monilinia laxa in North America?

Answer 34

Yes - California

Question 35

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

Answer 35

blossom blight or twig canker

Question 36

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

Answer 36

rot of ripening fruit

Question 37

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

Answer 37

Wet

Question 38

Where does the brown rot of stone fruits pathogen overwinter?

Answer 38

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

Question 39

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

Answer 39

blossom blight twig blight twig canker fruit rot

Question 40

Where does blossom blight enter the plant?

Answer 40

through the pistil

Question 41

Does blossom blight have multiple reproductive cycles?

Answer 41

Yes

Question 42

What is a symptom of blossom blight?

Answer 42

Gummy exudates

Question 43

What do infected fruit of brown rot eventually turn into?

Answer 43

black mummies

Question 44

Do black mummies fall from the tree?

Answer 44

sometimes

Question 45

Where do main infections of brown rot originate from?

Answer 45

black mummies on the ground

Question 46

How fast can mature fruit decay from brown rot?

Answer 46

2 days

Question 47

Can brown rot remain dormant in the fruit growing season?

Answer 47

Yes - often remains inactive until fruit matures.

Question 48

Where do apothecia occur on mummified fruit?

Answer 48

only on fallen fruit (not common in nature)

Question 49

What are apothecia?

Answer 49

small mushroom like structures

Question 50

Does apothecia occur on fruit on the tree?

Answer 50

No, only on fallen fruit

Question 51

Does brown rot have secondary infections?

Answer 51

Yes

Question 52

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

Answer 52

blossoming

Question 53

How is brown rot of stone fruits controlled?

Answer 53

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

Question 54

What is the causal agent of peach leaf curl?

Answer 54

Taphrinia deformans (a fungi)

Question 55

What is the causal agent of cherry leaf curl?

Answer 55

Taphrinia cerasi (a fungi)

Question 56

Where can you find peach and cherry leaf curl?

Answer 56

worldwide

Question 57

Where do primary infections occur in leaf curl?

Answer 57

early spring from bud swell

Question 58

Where do the most common symptoms of leaf curl occur?

Answer 58

on the leaves

Question 59

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

Answer 59

uncontrolled replication of meristematic cells

Question 60

Does leaf curl cause fruit drop?

Answer 60

Yes

Question 61

Does leaf curl infect the fruit of the tree?

Answer 61

Yes - but it is rare

Question 62

How can leaf curl be controlled?

Answer 62

fungicide in Autumn - after leaves have fallen or | in spring - before bud swell

Question 63

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

Answer 63

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

Question 64

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

Answer 64

after leaves have fallen

Question 65

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

Answer 65

before bud swell

Question 66

What stone fruits does scab appear on?

Answer 66

peaches | nectarines

Question 67

What is the causal agent of scab?

Answer 67

fungus - Cladosporium carpophilum

Question 68

Does the same agent cause scab on cherry and peaches?

Answer 68

No

Question 69

Does scab resemble cankers?

Answer 69

Yes

Question 70

When do scab symptoms occur on fruit?

Answer 70

when fruit is about half grown

Question 71

What does scab look like on fruit?

Answer 71

small greenish circular spots on fruit surface that expand over time

Question 72

Does scab lead to fruit cracking?

Answer 72

Yes

Question 73

How does scab overwinter?

Answer 73

as mycelia on twigs | as chlamydospores on the bark surface

Question 74

How can scab be controlled?

Answer 74

fungicides only

Question 75

What fungicide can be used on fruit scab?

Answer 75

calyx split (benzimydazole)

Question 76

What two bacteria are pathogenic for stone fruits?

Answer 76

Bacterial spot | Bacterial canker

Question 77

What does bacterial spot symptoms look like?

Answer 77

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

Question 78

Does bacterial spot of stone fruits cause shot hole symptoms?

Answer 78

Yes

Question 79

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

Answer 79

Spring cankers | Summer cankers

Question 80

What bacterial spot canker occurs on past seasons growth?

Answer 80

Spring

Question 81

What bacterial spot canker occurs on this seasons growth?

Answer 81

Summer

Question 82

Where does bacterial spot overwinter?

Answer 82

infected twigs

Question 83

What does bacterial spot require for infection to occur?

Answer 83

water congestion

Question 84

What is the most effective way to control bacterial spot?

Answer 84

Avoid highly susceptible cultivars

Question 85

What bacterial cause bacterial canker?

Answer 85

Pseudomonas syringae

Question 86

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

Answer 86

gumming

Question 87

What environmental conditions favor bacterial canker?

Answer 87

prolonged periods of cold, wet weather

Question 88

Is Pseudomonas syringae resistant to copper?

Answer 88

Yes

Question 89

Is copper safe to use on stone fruits?

Answer 89

No - it damages most stone fruit trees