1. 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

2. 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.

3. Apple Diseases
Apple Scab
Fire Blight
Cedar Apple Rust
Black Rot

4. 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

5. James Peale, 1824

6. 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

7. Symptoms

8. Symptoms

9. Signs
pseudothecia

10. Signs

12. Symptoms

13. 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.

14. 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

15. Disease Cycle – Apple Scab

16. 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

17. 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

18. 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

19. Symptoms –

20. 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 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

21. Disease Cycle

22. Control
Eradication 1-2 miles of orchards – red cedars, 4-5 miles more effective
Resistance
Chemical

23. 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

24. 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

25. Symptoms
Apple Shoot
Pear Blossom

26. Symptoms (Shepard’s Crook)

27. Symptoms
Burnt Appearance
Diseased shoot on left

28. 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)

29. Disease Cycle – Fire Blight

30. 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

31. 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

32. 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

33. Symptoms

34. Symptoms

35. Symptoms

36. 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

37. 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