Stone Fruit Diseases Flashcards
Give examples of stone fruits. (7)
Apricot, Peach, Nectarine, Prune, Plum, Cherry, Almond
What Genus do stone fruits belong to?
Prunus
What is the worst stone fruit disease?
Sharka disease (Plum pox virus)
How many trees are infected by the Plum pox virus?
Over 100 million
Which fruit does the plum pox virus produce ringspot symptoms on? (Only one in the world)
Apricot - on the stones
Is premature fruit drop a symptom of plum pox virus?
Yes
Where and when was the plum pox virus first discovered?
Bulgaria (1915)
When and where was the plum pox virus first discovered in the western hemisphere?
Chili (1992)
What strain of the plum pox virus is in the USA? What year was it discovered?
Strain D (1999)
What other stone fruits does PPV-Strain D infect? (3)
peach, nectarine, and apricot
not cherry
How many years did it take to eradicate PPV-D from Pennsylvania?
7 years (1999-2006, with last positive recorded in 2006)
What is a critical component of any eradication program?
Extensive survey (testing samples)
What plant factors affect PPV-D symptoms? (4)
age
nutrition
status
cultivar
Where do symptoms of PPV appear? (4)
Leaves
Fruits
Flowers
Seeds
How are potyviruses transmitted?
by aphids in a non-persistent way
Where is the only place in the world to find PPV-D?
North America
Name two vectors of PPV.
Aphids
Humans
Is PPV seed transmissible?
No, or very low (single study)
How many species of Aphids transmit PPV? (range)
4-6 main
20 total
How many trees are tested within 1 mile of a positive PPV test?
All of them (8 leaves per tree)
Individual tests
How many trees are tested within 5 miles of a positive PPV test?
All of them (4 leaves per tree)
Two trees per test
What are the two most important control measures for PPV?
Early detection
Removal and destruction of infected trees
What is the primary host of X-disease?
Peaches
What is the secondary host of X-disease?
Cherry
List symptoms of X-disease. (4)
Leaves curl inward
Leaves change yellow to reddish-purple spots
Leaves fall prematurely
Fruit drops prematurely
What type of organism causes X-disease?
Phytoplasma
Define phytoplasma
Phytoplasmas are obligate bacterial parasites of plant phloem tissue and of the insect vectors that are involved in their plant-to-plant transmission.
How can X-disease be controlled?
Removal of infected trees
Insecticides against leafhoppers
Removal of secondary hosts
What is the vector of X-disease?
Leafhopper
What is oxytetracycline used for?
Trunk injection can provide temporary symptom remission of X-disease.
What is the causal agent of brown rot of stone fruits?
a Fungi
What is Monilinia fructicola?
What is Monilinia laxa?
the causal agent of brown rot of stone fruits
Is Monilinia fructicola in North America?
No
Is Monilinia laxa in North America?
Yes - California
What does an early infection of brown rot of stone fruits look like?
blossom blight or twig canker
What do late infections of brown rot of stone fruits look like?
rot of ripening fruit
Does brown rot of stone fruits cause more damage in wet or dry years?
Wet
Where does the brown rot of stone fruits pathogen overwinter?
mummified fruits from the previous season that remain attached to the tree or fall to the ground.
What other infections does brown rot cause (same pathogen)?
blossom blight
twig blight
twig canker
fruit rot
Where does blossom blight enter the plant?
through the pistil
Does blossom blight have multiple reproductive cycles?
Yes
What is a symptom of blossom blight?
Gummy exudates
What do infected fruit of brown rot eventually turn into?
black mummies
Do black mummies fall from the tree?
sometimes
Where do main infections of brown rot originate from?
black mummies on the ground
How fast can mature fruit decay from brown rot?
2 days
Can brown rot remain dormant in the fruit growing season?
Yes - often remains inactive until fruit matures.
Where do apothecia occur on mummified fruit?
only on fallen fruit (not common in nature)
What are apothecia?
small mushroom like structures
Does apothecia occur on fruit on the tree?
No, only on fallen fruit
Does brown rot have secondary infections?
Yes
When is the worst time for wet weather in regards to brown rot of stone fruits?
blossoming
How is brown rot of stone fruits controlled?
fungicides
resistance to benzimidazoles
removal of mummies (cultural control)
rapid cooling after harvesting
What is the causal agent of peach leaf curl?
Taphrinia deformans (a fungi)
What is the causal agent of cherry leaf curl?
Taphrinia cerasi (a fungi)
Where can you find peach and cherry leaf curl?
worldwide
Where do primary infections occur in leaf curl?
early spring from bud swell
Where do the most common symptoms of leaf curl occur?
on the leaves
What is the underlying method that leaf curl causes the symptoms?
uncontrolled replication of meristematic cells
Does leaf curl cause fruit drop?
Yes
Does leaf curl infect the fruit of the tree?
Yes - but it is rare
How can leaf curl be controlled?
fungicide in Autumn - after leaves have fallen or
in spring - before bud swell
Does a fully mature leaf have to be protected from leaf curl?
No, it is naturally resistant. Leaf curl only attacks younger leaves
When does fungicide application need to be applied in the Autumn?
after leaves have fallen
When does fungicide application need to be applied in the spring?
before bud swell
What stone fruits does scab appear on?
peaches
nectarines
What is the causal agent of scab?
fungus - Cladosporium carpophilum
Does the same agent cause scab on cherry and peaches?
No
Does scab resemble cankers?
Yes
When do scab symptoms occur on fruit?
when fruit is about half grown
What does scab look like on fruit?
small greenish circular spots on fruit surface that expand over time
Does scab lead to fruit cracking?
Yes
How does scab overwinter?
as mycelia on twigs
as chlamydospores on the bark surface
How can scab be controlled?
fungicides only
What fungicide can be used on fruit scab?
calyx split (benzimydazole)
What two bacteria are pathogenic for stone fruits?
Bacterial spot
Bacterial canker
What does bacterial spot symptoms look like?
angular spots on the leaves along the main vain and along outer part of the leaf
Does bacterial spot of stone fruits cause shot hole symptoms?
Yes
What are the two cankers caused by bacterial spot of stone fruits?
Spring cankers
Summer cankers
What bacterial spot canker occurs on past seasons growth?
Spring
What bacterial spot canker occurs on this seasons growth?
Summer
Where does bacterial spot overwinter?
infected twigs
What does bacterial spot require for infection to occur?
water congestion
What is the most effective way to control bacterial spot?
Avoid highly susceptible cultivars
What bacterial cause bacterial canker?
Pseudomonas syringae
What is a mark of bacterial canker on the bark of the tree?
gumming
What environmental conditions favor bacterial canker?
prolonged periods of cold, wet weather
Is Pseudomonas syringae resistant to copper?
Yes
Is copper safe to use on stone fruits?
No - it damages most stone fruit trees
