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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.

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Pome fruits
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

Most popular varieties
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.

Apple diseases
Apple Diseases

  • Apple Scab

  • Fire Blight

  • Cedar Apple Rust

  • Black Rot

Apple scab
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

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

  • FruitScabs - 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



Economic impact
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.

Disease cycle
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


  • 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

Cedar apple rust
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

Symptoms –


  • Leaf - bright yellow leaf spots that turn orange as enlarge and age.

  • Fruit and twig – infections occur

  • These symptoms caused by fungus aecial stage.


  • 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

Disease cycle1
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

Disease cycle2
Disease Cycle


Eradication 1-2 miles of orchards – red cedars, 4-5 miles more effective




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 1900’s

  • 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


  • 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


Apple Shoot

Pear Blossom


Burnt Appearance

Diseased shoot on left

Disease cycle3
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)


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

Black rot
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


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

Disease cycle4
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


-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