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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 • 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 • 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 Scab • Fire Blight • Cedar Apple Rust • Black Rot
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
Signs pseudothecia
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 • 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
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
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 – 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
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
Control Eradication 1-2 miles of orchards – red cedars, 4-5 miles more effective Resistance Chemical
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 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
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
Symptoms Apple Shoot Pear Blossom
Symptoms Burnt Appearance Diseased shoot on left
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)
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
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
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
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
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
