Pome fruits

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Pome fruits

• Grown in the temperate zones in both hemispheres.
  Most production is in the cooler sections of US,
  Canada and Europe. Not below Memphis and Fort
  Smith AR.
• Apples 1 pome fruit with most production in the
  Pacific NW, in the valleys where climate is dry
  and the crops are irrigated.
• 1991 9,871 million pounds
• Leading States 71 of total production
• Washington 4,300 million lbs
• New York 1,050 million lbs
• Michigan
• Calif.
• PA, VA, NC, WVA, OR, ID, OH, and IL

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Most popular varieties

• Red and Yellow Delicious
• McIntosh
• Rome Beauty
• York
• Jonathan
• Recently Granny Smith, Gala, Fiji
• Fresh market highest prices, remainder of crop
  is process for juice, sauce, jelly or jam.

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Apple Diseases

• Apple Scab
• Fire Blight
• Cedar Apple Rust
• Black Rot

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Apple Scab

• Pathogen
• Venturia inequalis sexual
• Spilocaea pomi -asexual
• Responsible for crop failures in the late 1800s.
  Present in all countries where apples are grown.
  Not a problem in dry, irrigated locations, but
  where cool moist wet spring months are common

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James Peale, 1824
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Symptoms

• Fruit, leaves, leaf petioles, and young twigs
  attacked causing scabby lesions in which tissues
  may be killed.
• Leaf - spots, black in color and appear on both
  surfaces and leaf may curl or distort
• Fruit Scabs - appear similar on fruit but the
  fungus stimulates cork formation beneath spots
  that may cover the fruits and result in severe
  fruit disfiguration
• Twigs infections easily overlooked as the
  lesions look like enlarged lenticels
• Fungus attacks only current season growth

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Symptoms
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Symptoms
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Signs
pseudothecia
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Signs
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Symptoms
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Economic impact

• Greater than most diseases because
• Crop reduction (Defoliation- weakening)
• Lowering of fruit grade
• Foliage loss
• Increase in production costs Fungicides Prior
  to fungicides, total fruit drop appeared
  dormant in June.

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Disease Cycle

• Fungus overwinters in leaves on ground and
  sometimes on apple buds
• Late fall spring pseudothecia are produced in
  leaves Primary infection in new growth
• Olive, two-celled ascospores Primary Inoc.
  Ejected into air
• Conidia produced in apple bud scales
• Ascospores and conidia infect flowers and leaves
• Secondary cycle conidia produced in primary
  lesions, 7-9 days after infection
• Spread by splashing rain and by wind.
• Infected fruit may not show symptoms until
  storage after several months
• Inoculum level in spring may be high after spray
  because overwintering in leaves

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Disease Cycle Apple Scab
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Control

• Hosts Cultivated apple and crab apple species.
  Not to pear
• Resistance
• Sanitation not feasible
• Chemical - 1, protectant prevent spores from
  germinating, postinfection fungicides some
  resistance in fungal populations

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Cedar Apple Rust

• Pathogen Gymnosporangiuim juniperi-virginianae
  Basidiomycete
• Name comes from fact that red cedar (Juniperus
  viginianae) is alternate host
• Other species cause quince rust and hawthorn rust
• Economic impact due to apple tree defoliation
  that results in fruit yield and size reduction
  and also a reduction in tree vigor

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Symptoms

• Apple
• Leaf - bright yellow leaf spots that turn orange
  as enlarge and age.
• Fruit and twig infections occur
• These symptoms caused by fungus aecial stage.
• Cedar
• Leaf - Brown to reddish brown leaf galls -During
  periods of rain, galls produce orange, gelatinous
  spore-horns from the gall surface that contain
  masses of teliospores.
• Teliospores germinate and each cell produces 4
  basdiospores that are airborne to apples

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Symptoms
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Disease Cycle

• Two host and three fruiting structures
• Apple, cedar - telia, aecia, and pycnia
• OW in reddish brown galls cedar apples in cedar
  tree
• Wet in spring horns with teliospores, each
  produces 4 basidiospores
• Air currents (3-5 kilometers) germ tubes leaf
  and fruit of apples, temp and wetting conditions
  4-8 d old leaves - spermagonia that is
  fertilized by compatible spermatia production
  of aecia
• July and August windborne aeciospores (produced
  in chains) from apple infect cedar leaves 1-3
  weeks rust lesion
• fungus grows in tissue in winter18 months after
  infection production of galls

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Disease Cycle
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Control

• Eradication 1-2 miles of orchards red cedars,
  4-5 miles more effective
• Resistance
• Chemical

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Fireblight

• Pathogen Erwinia amylovora bacterium
• This was the first plant disease proven to be
  caused by a bacterium
• Pear industry in Eastern U.S. was essentially
  wiped out by this disease in 1900s
• Pear is considerably more susceptible than apple,
  - most destructive disease of apple
• Economic impact Results from killing of
  flowers, fruit spurs, twigs and girdling of large
  branches and trunks that results in death of the
  trees
• Young trees in nursery or orchard can be
  killed in a single season.
• Hosts over 75 rosaceous plant species are
  susceptible

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Symptoms

• Flower and twig blight appears in spring,
  blackening of flowers and leaves curled leaves
  hanging from twigs and small branches
• Fruits first as watersoaked lesion, then
  mummifies and turn black and may be tree for
  several months
• Fruit spurs and terminal twigs Infections and
  symptoms progress to supporting branches where
  cankers are formed.
• Sign During humid conditions, milky bacterial
  ooze may appear on surface of infected part
  rod-shaped with flagella

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Symptoms
Apple Shoot
Pear Blossom
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Symptoms (Shepards Crook)
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Symptoms
Burnt Appearance
Diseased shoot on left
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Disease Cycle

• Bacteria overwinter in canker margins in branches
• Warm spring weather multiplication
• Sticky bacterial exudates is present insects are
  attracted and pickup ooze on their bodies and
  transfer to flowers where new infections take
  place
• Splashing rain may also spread the bacteria
  (enter through natural and wound openings)

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Disease Cycle Fire Blight
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Control

• 3 Areas of Importance
• I. Reducing bacterial inoculum
• Removal by pruning the overwintering cankers
• Weekly inspection of orchards in summer, and
  removal of infected spurs and terminals
• Disinfect tools
• II. Properly timed application of bactericides
  during flowering to control blossom blight phase
• Cu
• Streptomycin 2-3 applications
• III. Insect control esp. aphids and plant bugs to
  prevent infections
• IV. Avoid planting susceptible cultivars
• V. Apples more resistant
• VI. Over stimulation (succulent growth part.
  Susc.) with high N should be avoided

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Black Rot

• Pathogen Botryosphaeria obtuse-
• Economic Effects
• Limb Canker phase is most important in the
  northeastern and north central apple-growing
  regions of the United States
• Leaf Spot and fruit rot phase are most important
  in the southeast

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Symptoms

• Appear 1 to 3 weeks after first petal fall
• -leaf infections begin as small purple flecks
  rapidly enlarging to 1/8 to 1/4 in. diameter.
• -Margins remain purple, center turns brown frog
  eye appearance
• Infections on young fruit
• -reddish flecks, developing into purple pimples
• -enlarge to dark brown necrotic areas
• Infections on more mature fruit
• -Black, irregularly shaped
• -surrounded by red halo
• -enlarging characterized by series of
  concentric rings alternating black to brown
• Infected fruit mummify and remain attached to
  tree
• Limbs and branches
• -reddish brown and slightly sunken cankers large
  and small
• -branches weak break with heavy crop load

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Symptoms
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Symptoms
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Symptoms
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Disease Cycle

• -Over-winters in dead bark, twigs, cankers, and
  mummified fruit
• -Ascospores (spring) and conidia released during
  rainfall washed or blown onto fruit or foliage
• -Sepal infection occurs after bud break
• -Fruit infection occurs during growing season
• -Leaf infection common after petal fall
• -Early season infection may result in fruit drop

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Control

• -Removing dead wood, mummies cankers from trees
• -Current season prunings should be removed form
  the orchard or chopped with a flail mower
• -Fungicides, applied from silver tip until
  harvest required to control disease