Transcript Apples - OARDC - The Ohio State University

Plant Health Management
for Backyard Apple
Plantings
Prepared by
Mike Ellis
Professor and Extension Specialist
and
Omer Erincik
Graduate Research Assistant
Department of Plant Pathology
The Ohio State University
OARDC/OSUE
Wooster, OH, 44691
Early Season Diseases of
Apple
Apple scab
Cedar apple rust
Powdery mildew
These diseases develop in the orchard
between bud break and early to mid
summer.
Control measures for these diseases need
to be conducted during this period.
Apple scab
Symptoms:
On leaves:
 Velvety olive-green spots with
unclear margin appear on the leaves.
 Later, the lesions enlarge, and
become darker with more distinct
margins.
 Heavily infected leaves become
distorted and drops early in the
summer.
On fruit:
 Spots are similar to those found on
leaves.
 Spots darken with age and become
black and “corky” or “scabby”.
 Scabs are only skin deep.
 Cracks often develop on these
scabby areas.
Apple scab
Disease Development:
Caused by the fungus Venturia inaequalis.
The fungus overwinters in the previous year's
diseased leaves that have fallen under the
tree.
In the April, May and June, the fungus
produces millions of spores in the old leaves
on the ground. These spores are shot into the
air and carried by the wind or splashing rain
to young leaves, flower parts and fruits.
 A free film of water on leaves and fruit is
required for the spores to germinate and
infection to occur.
Cedar-apple rust
Symptoms:
On upper side of the leaves:
 Pale yellow or orange spots appear during
May or June.
 Small black fungal fruiting bodies (pycnia)
form within the spots and may exude an
orange fluid.
On lower side of the leaves:
 During late spring and early summer,yellow
spots develop on the underside of the leaf.
 Within these spots a number of small,
orange-yellow tubular projections (aecia)
appear. Infected leaves may turn yellow and
drop.
 Defoliation of rusted leaves is most
common in dry summers.
Cedar-apple rust
Symptoms:
On Fruit:
 Similar yellow-orange spots
appear, usually at or near the
calyx end.
 These spots are much larger
than the spots on leaves.
 The tube-like aecia may form on
the slightly raised fruit lesions.
 Infected fruits are often stunted
and misshapen, and may drop
early.
Cedar-apple rust
Disease development:
 Caused by the fungus
Gymnosporangium juniperivirginianae.
 The fungus overwinters as mycelium in
galls on juniper or cedar. Large yellow
to orange gelatinous sporehorns are
formed on the galls in the spring and
spores (teliospores) are produced.
 Each teliospore germinates and
produces four to eight sporidia or
basidiospores.
Cedar apple rust
Disease development:
 Sporidia are carried by wind to nearby apple
leaves, fruits, and twigs where they penetrate the
cuticle and lesions develop on the upper leaf
surface and on fruit.
 After 10 to 14 days, the orange to black pycnia
develop in the spots on the upper leaf surface.
 Several weeks later, the aecia form on the under
leaf surface. The aecia produce another type of
spore (aeciospores) that are carried by wind to
junipers or cedars, where they cause infections
resulting in galls; thus, completing the disease
cycle.
Powdery mildew
Symptoms:
 Small, whitish patches of fungal growth
appear and quickly cover the entire leaf.
 Diseased leaves become narrow, crinkled,
stunted and brittle.
 Infected blossoms shrivel and produce no
fruit.
 By mid-summer, tiny, black round specks
(fungal fruiting bodies) show up on the
surfaces of the infected areas.
 Fruit symptoms are not usually seen unless
the disease has built up to high levels on
susceptible cultivars. Diseased fruit have a
fine network type surface blemish called
russetting.
Powdery mildew
Disease development:
 Caused by the fungus, Podosphaera leucotricha.
 The fungus overwinters as mycelium in terminal buds
and twig tips infected during the previous year.
 As buds break dormancy, the powdery mildew fungus
resumes growth and colonizes developing shoots
causing primary infections.
 The powdery white appearance on infected shoots
consists of many thousands of spores which are
responsible for spreading the fungus later in the
growing season.
 Powdery mildew infections occur when the relative
humidity is greater than 90% and the temperature is
between 50-77 degrees F.
 Free water is not required for infection.
Management of Early Season
Apple Diseases
Free water (wet conditions) is required for
most fungal pathogens to infect plants.
Any practice that promotes faster drying
of fruit and foliage is beneficial for disease
control.
Site selection
 Select a site with good air movement all-day
sun light, and good soil drainage.
 Do not plant trees in shaded areas.
Management of Early Season
Apple Diseases
Canopy management
 Control timing and amount of nitrogen
fertilizer to prevent excessive growth.
 Prune out and destroy all dead or diseased
shoots and limbs while trees are dormant
(mid-March is usually a good time).
 Prune healthy growth to improve air
movement and sunlight penetration, to
minimize shading and decrease drying time
of leaves and fruit during the growing
season.
Management of Early Season
Apple Diseases
Sanitation
 Apple scab-Rake and destroy fallen leaves
including those from nearby crabapple, before
growth starts in the spring.
 Cedar-apple rust-Remove nearby infected cedars
or junipers. If infected plants are not removed,
remove all galls in winter or early spring before
sporehornes form.
 These sanitation measures will reduce the
number of spores that can initiate these diseases.
Fungicides
 On susceptible varieties, fungicides may be
required to obtain an acceptable level of disease
control.
Management of Early Season
Apple Diseases
 Use of disease resistant apple varieties
Several apple varieties have high level of resistance
to apple scab, cedar-apple rust and powdery mildew.
The following varieties have good resistance to all
three diseases and are ideal for backyard production.
Using these cultivars should eliminate the need for
fungicides to control the early season disease
complex.
 Early season varieties: Redfree, Prima, Jonafree,
Sir Prize
 Mid-season varieties: Novamac, Liberty, Freedom
 Late-season varieties: Enterprise, Goldrush
Other disease resistant varieties are available.
Management of Early Season
Apple Diseases
 Use of disease resistant apple varieties
Most other apple varieties, including most
commercially grown varieties are susceptible to all
three early season diseases; however, they differ
in their degree of susceptibility. Information on
these varieties and their level of susceptibility to
various diseases is available in “selected literature
for backyard fruit production and plant health
management” provided at the end of this
presentation.
Use of varieties with high levels of susceptibility
will probably require some level of fungicide use
for control of the early season diseases.
Avoid using highly susceptible varieties.
Late Season or “Summer”
Diseases of Apple
Sooty blotch
Fly speck
Black rot
White rot
 These diseases develop in the orchard from
shortly after petal fall through harvest; therefore,
they are often referred to as “summer diseases”.
 Control measures for these diseases need to be
conducted during this period.
Sooty blotch and Fly speck
Symptoms:
Sooty blotch:
 Brown to dull black, sooty blotches
form on the fruit surface.
 The fungus is restricted to the outer
surface of the fruit, and in many cases
the blotches can be easily rubbed off.
Fly speck:
 Groups of 6 to 50 or more black and
shiny round dots appear on the
surface of the fruit.
 Like sooty blotch, fly speck infections
are superficial; however, they are
usually harder to rub off than sooty
blotch.
Sooty blotch and flyspeck
Disease development:
 Pathogens:
Sooty blotch ….Caused by a complex of several fungi
Fly speck… Caused by the fungus Zygophiala jamaicensis
 Both pathogens overwinters on wild plants,
especially brambles in or near to the orchard.
 In spring, they produce large numbers of spores on
their wild hosts.
 The spores are then spread by splashing water or
wind blown mists into orchards from late May or
early June until fall.
 The conidia infect apple twigs and fruit under cool,
humid weather conditions (optimum 65 degrees F).
Black Rot and Frogeye Leaf Spot
Symptoms:
On fruit: Black Rot
 At first, a light brown spot form on the
fruit.
 With time, the spots enlarge and
commonly develop a series of brown
and black concentric bands or rings.
 The rotted fruit finally turns black. The
decayed tissue remains firm to leathery,
and holds its original shape until the
entire fruit is rotted.
Rotted fruit shrivel into mummies and often remain attached to
the tree.
Black, pimple-like fruiting bodies (pycnidia) of the causal fungus
appear on the surface of rotted fruit.
Black Rot and Frogeye Leaf Spot
Symptoms:
On leaves: Frogeye leaf spot
 Round to irregularly lobed spots develop a
light brown-to-gray center surrounded by
one or more dark-brown concentric rings
and a purple margin giving it a "frogeye"
appearance.
 Black pycnidia may develop on the upper
surface in the centers of the older leaf spots.
On branches:
 Small, slightly sunken, reddish-brown areas
develop in the bark. These areas slowly
enlarge and darken to form cankers.
 Cankers may continue to expand a little
each year, and may extend down the limb for
3 feet or more.
Black Rot and Frogeye Leaf Spot
Disease development:
 caused by the fungus, Physalospora obtusa.
 The fungus overwinters in cankers, mummified fruits, and the bark
of dead wood.
 In the spring, the fungus produces spores on these previously
infected plant parts.
 The heaviest release of spores occurs around blossom time, but
the production of spores may continue during wet periods
throughout the summer.
 Leaf infection usually occurs during the petal-fall period.
 Fruit infection can occur as early as petal fall; however, symptoms
are usually not visible until mid to late-summer as the apple
approaches maturity.
 A film of free water on plant surface and temperatures of 75-80
degrees F are favorable for spore germination and host infection.
White Rot
Symptoms:
On fruit:
 At first, small, reddish-brown spots appear around
the lenticels.
 The spots enlarge and become slightly depressed.
On yellow-skinned varieties, these spots may be
bordered by one or more red "halo" rings.
 The tissue under the spots is soft and the rotted
area is egg shaped.
On branches:
 Small, circular spots or "blisters" appear on the
twigs in June and July.
 The spots enlarge, become somewhat sunken,
and fill with a watery fluid.
 Infected areas are slightly sunken and eventually
form dark colored cankers.
White Rot
Disease development
 caused by the fungus Botryosphaeria dothidea.
 The fungus overwinters on living and dead cankered limbs
and in rotted fruits.
 In the spring, the fungus produces spores in these previously
infected plant parts.
 The spores are rain-splashed or blown to other parts of the
tree during rainy periods.
 Wounds or breaks in the epidermis are necessary for the
fungus to penetrate.
 Apple fruits may become infected fairly early in the season,
but fruit rot does not develop much until the fruit is almost
mature.
 At temperatures above 75 degrees F, mature fruit may rot
completely within a few days after infection.
Management of “Summer”
Diseases
(Sooty blotch, Fly speck, Black rot, and
White rot)
Free water (wet conditions) is required for
these fungal pathogens to infect plants.
Any practice that promotes faster drying
of fruit and foliage is beneficial for disease
control.
Site selection
 Select a site with good air movement all-day
sun light, and good soil drainage.
 Do not plant trees in shaded areas.
Management of “Summer”
Diseases
Canopy management
 Control timing and amount of nitrogen fertilizer
to prevent excessive growth.
 Prune trees annually during the dormant season
(mid-March is usually a good time). Opening up
to tree canopy results in improved air movement
and sunlight penetration . This reduces shading
and decreases drying time of fruit and foliage.
Remove wild hosts
 Remove and destroy nearby wild or neglected
apple trees. Wild brambles (raspberry and
blackberry) serve as a reservoir for sooty blotch
and fly speck and should be removed.
Management of “Summer”
Diseases
Sanitation – Black rot and White rot
 Prune out and destroy all dead wood, cankers,
and black rot mummies.
Fungicides
 Especially if fruit rots are a problem, fungicides
may be required to obtain an acceptable level of
disease control.
Special Note: Since sooty blotch and fly speck are
superficial and rarely affect fruit quality, removal of
the fungus by washing, rubbing, or pealing fruit
results in fruit that is acceptable for cooking or
eating fresh.
Other important Diseases
of Apple
Phytophthora Crown and Root Rot
Symptoms:
Above ground
 Infected trees may decline slowly
over one or more years, or they
may collapse and die rapidly.
 On declining trees, leaves are
small and chlorotic (yellow) when
compared to leaves on healthy
trees.
 On trees that decline gradually, a
reddish or purple discoloration of
the leaves often occurs in
autumn, while leaves on healthy
trees remain green.
Phytophthora Crown and Root Rot
Symptoms:
Below ground
 A diagnostic reddish-brown
discoloration of the inner bark and wood
can be observed on the crown or main
roots of infected plants.
 A sharp line separates the reddishbrown (diseased) and white (healthy)
portion of the crown.
Phytophthora Crown and Root Rot
Disease development:
 caused by several species of the fungus Phytophthora.
 The fungus overwinters and persists in soil for many years.
 The fungus requires extremely wet or saturated soils in order
to infect and cause significant damage; thus good soil
drainage is important for control.
 When soils are saturated, the fungus produces spores, called
zoospores. Zoospores use flagella to swim to susceptible
plant tissue where they cause infection.
 The longer the period or periods of soil saturation, the greater
the risk of infection.
 Some species may also be introduced to the orchard on
contaminated planting stock or through movement of
contaminated soil.
Management of Phytophthora
Crown and Root Rot
Proper site selection
Plant in well-drained soil.
Select a site that does not have a previous history
of problems with collar rot.
Use disease resistant rootstocks
Pears are resistant to collar rot.
Collar rot resistance in various apple rootstocks:
Resistant…………………M-2, M-4, M-9, Ottawa
Moderately resistant…….M-7, M-11
Susceptible……………….M-26, MM-106
Highly susceptible………..MM-104
Fire Blight of apple and pears
Symptoms:
 Blossoms become water-soaked and turn
brown.
 Infected twigs become blighted, turning
brown on apple and black on pear.
 The end of the branch may bend over,
resembling a shepherd's crook .
 Blighted leaves remain attached to the
dead branches throughout the summer.
 The bark sometimes cracks along the
margin of the infected area on longer
branches causing a distinct canker.
 Fruit may be blighted. Rotted areas turn
brown to black.
 Droplets of milky tan-colored bacterial
ooze may be visible on the surface of
diseased tissue.
Fire Blight
Disease development:
 Caused by the bacterium, Erwinia amylovora.
 The bacteria overwinter in living tissue at the margins of
cankers on the trunk and main branches.
 The bacteria become active in the spring . Their growth is
favored by rain, heavy dews, and high humidity.
 A single active canker may produce millions of bacteria,
enough to infect an entire orchard.
 The bacteria in droplets of ooze are spread by splashing rain
or insects (mostly bees, flies, and ants) to open blossoms.
 Invasion can occur directly through natural openings, such as
lenticels and stomata, under conditions of prolonged rain and
high humidity.
Management of fire blight

Pruning



Proper fertilization


Prune out blighted twigs and cankers during the dormant
season. This may decrease the pathogen inoculum level
for the following season.
If blighted twigs are pruned out during summer, cuts
should be made l2 to l5 inches below diseased wood and
pruning tools should be disinfested by dipping in a 2:10
solution of household bleach in water after each cut.
Excessive nitrogen fertilizer and heavy pruning will
promote vigorous growth of succulent tissue which is
more susceptible to fire blight. Avoid excessive use of
nitrogen fertilizer and apply fertilizer only in the spring.
Control insects

Sucking insects create wounds through which fire blight
bacteria can enter.
Management of fire blight
Use resistant varieties
Apple
Moderately resistant: Jonafree,
Melrose, Northwestern Greenings,
Nova, Easygro, Prima, Priscilla,
Quinte, Red Delicious, Redfree, Sir
Prize, Winesap.
Moderately susceptible: Dutches,
Empire, Golden Delicious,
Haralson, Jonagold, Jonamac,
Jerseymac, Liberty. McIntosh,
Minjon, Northern Spy, Novamac,
Spartan
Highly susceptible: Beacon, Cortland,
Fuji, Gala, Granny Smith, Idared,
Jonathan, Lodi, Monroe, Mutsa
(Crispin), Paulared, Roma, Beauty,
Wayne, Wealthy, Yellow
Transparent.
Pears
Resistant: Ayers Kieffer,
Magness, Moonglow, Potomac,
Honeysweet, Harrow Sweet,
Horrow Delight, Monterey, Tyson
Moderately resistant: Dawn,
Douglas, Garber, Seckel,
Spartlett, Luscious, Lincoln,
Harvest Quenn, Worden Seckel
Highly Susceptible: Aurora,
Barlett, Bosc, Clapp,s Fovarite,
Red Barlett, Reimer Red,
Starkrimson
Using Fungicides For Apple
Disease Control
 Fungicides are very important for disease
control in commercial apple production, and
may be required in backyard apple production
if highly susceptible varieties are grown;
however, the emphasis for disease control in
backyard apple production should be placed
on the use of disease resistance and the
various cultural practices previously
mentioned.
Using Fungicides For Apple
Disease Control
If diseases such as apple scab, cedarapple rust, powdery mildew or fruit rots
become established in the planting,
fungicides may be required in order to
obtain acceptable fruit quality.
There are a few fungicides available for
homeowners that should be useful in
backyard apple plantings.
For backyard growers
that do wish to use
fungicides in the disease
management program,
fungicide recommendations
are available for apples in
Bulletin 780 “Controlling
Disease and insects In Home
Fruit Planting”.
Selected literature for backyard fruit
production and plant health
management:
Bulletin 591. “Growing and Using Fruit at
Home”
Bulletin 780. “Controlling Diseases and
Insects in Home Fruit Planting”
“Midwest Tree Fruit Pest Management
Handbook”
These can be obtained through your county
extension agent or the Extension Publications Office,
The Ohio State University, 385 Kottman Hall, 2021
Coffey Road, Columbus, Ohio, 43210-1044
To get more information about plant
diseases visit the websites below.
http://www.ag.ohiostate.edu/~plantdoc/extension.php
http://www.ohioline.ag.ohio-state.edu