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 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

21. Disease Cycle

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

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. ► SignDuring 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 AppearanceDiseased 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