The diagnostic keys for deciduous tree fruit diseases were developed to aid field personnel in the identification of diseases that are common to the mid-Atlantic region of the United States. The keys are arranged to guide the user through a series of logically arranged statements describing symptoms and signs of fruit tree diseases. By selecting from a series of numbered statements, those which most closely describe observations made in the field, the user should be able to narrow the possibilities to only one or a couple of probable diseases. Clicking on the symptom description (if highlighted) will link to a photographic image of the symptom. Some disease names are linked to Fact Sheets containing additional information on biology and disease monitoring.

Many problems will not be diagnosed easily because some insect, rodent, bird, hail, and other mechanical damage, nutritional deficiencies, abiotic factors, herbicide injury, and other causes can often be mistaken for or appear concurrent with disease symptoms and signs. The more information that can be obtained, the greater the chance of arriving at the proper diagnosis. Be aware that the key is not complete for all possible diseases in the Mid-Atlantic region. Diseases of uncommon occurrence have not been included.

The following points should be considered when making a disease diagnosis.

1. Disease symptoms may vary slightly from season to season and on their time of appearance, often depending on environmental conditions.

2. It is essential to obtain fresh disease samples. Secondary organisms will often follow the primary pathogen and make diagnosis difficult or impossible.

3. The observer should record the varieties and rootstocks that are affected. Susceptibility of apple varieties and rootstocks to some diseases will vary greatly and may give a valuable clue to diagnosis.

4. The distribution of symptoms within an orchard and in individual trees will often aid in determining if the disorder is caused by a pathogen and how it spreads in the orchard.

5. Observe the areas surrounding the orchard for alternate hosts, abandoned orchards, and other sites of potential disease reservoirs. Observe the orchard configuration, contour, and soil type(s).

6. Complete records containing timings and rates of all pesticides, growth regulators, and fertilizers may be helpful in determining the problem.

7. Records of previous year's weather patterns, such as excessive rains, drought or extremely cold winter periods, along with grower cultural practices in the orchard may help in diagnosis.

8. A history of previous orchard problems should be obtained if possible.

The County Agricultural Extension Agent should be contacted if there are any further questions concerning diagnosis or control of these diseases.

To use the key, select a statement from the first set of statements which most closely describes your field observations. Continue to the next numbered statement that is specified by the line you've chosen. For example, when you read line 1a and you agree with the description as it pertains to your problem, go to line 2. If, after reading line 1a you disagree with it, then go to line 1b. If line 1b describes your symptom better than line 1a, then proceed to line 7. Continue through the key in this manner until a numbered statement suggests a particular diagnosis. If the diagnosis includes an underlined link, click the left mouse button to see the disease. When viewing the photograph, clicking the right mouse button will give you a list of options to save the image.  Close window after viewing photo by clicking the "X" in the upper right corner of the  window.

KEY TO APPLE DISEASE IDENTIFICATION

1a. General growth and vigor of the tree is reduced. Trees stunted or weakened. Foliage wilted or off-color with early reddening and defoliation in the fall. No other obvious symptoms on tree. (2)

1b. Obvious leaf, blossom, or fruit infections, cankers, galls or leaf variegation patterns. (7)

2a. Roots showing no obvious decay. (3)

2b. Roots, crown, and/or lower trunk showing obvious decay. (4)

3a. Fibrous roots lacking or showing witches broom. Most common on light-textured soils. NEMATODE DAMAGE (Pratylenchus penetrans)

3b. Distinct black sunken line at union apparent below bark. Trees may subsequently break at union. APPLE UNION NECROSIS (Tomato Ringspot virus)

3c. Bark missing at or below the soil line. Gnawing marks sometimes visible in wood. Callus formed in bark at margin of bare wood. RODENT DAMAGE

4a. Bark at crown and roots easily sloughs off exposing dense white fungus growth with fan shaped distribution at cambium. Black shoestring-like strands (rhizomorphs) may be obvious on surface of bark and yellow-brown mushrooms may appear at base of tree in late summer or early fall. ARMILLARIA ROOT ROT (Armillaria mellea)

4b. Decay present in root, crown and/or lower trunk area. Advancing margin of infection sometimes orange in color or slimy in appearance. Often a definite margin of infection. (5)

5a. Phytophthora isolated from decay . CROWN ROT (Phytophthora cactorum and other Phytophthora spp.)

5b. Wood slimy in appearance. Margin of decay may or may not be distinct. Decay may be restricted to interstem or rootstock only. Erwinia amylovora isolated from decay margins. FIRE BLIGHT (Erwinia amylovora)

5c. Phytophthora or Erwinia not recovered. (6)

6a. Funneled air space around base of tree where water collected and froze in contact with tree crown. WINTER FREEZE INJURY

6b. Roots in waterlogged soils appear blue to gray when cut into. ROOTS KILLED BY ASPHYXIATION

7a. Leaf spots, ooze, or obvious fungus fruiting bodies or growths on leaves, fruits, shoots, or wood. (8)

7b. Leaves showing distinct chlorotic or necrotic patterns on single branches or entire trees and locally or widely spread throughout orchard. Check for virus (apple mosaic virus, for example, nutritional disorder, pesticide injury or necrotic leaf blotch on Golden Delicious.

8a. Milky droplets of ooze exuded on the surface of infected blossoms , cankers, fruits or shoots during moist conditions. Infected tissues become scorched in appearance. Killed shoots often exhibit "Shepherd's crook" symptom. FIRE BLIGHT (Erwinia amylovora).

8b. Small to large, warty-appearing growths at crown or in roots. CROWN GALL (Agrobacterium tumefaciens) (Ohio State University).

8c. Infections occurring on leaves or fruits. (9)

8d. Cankers on wood 1 year old and older. (18)

9a. lnfections on leaves (may also be on fruits).(13)

9b. Infections on fruit only. (10)

10a. lnfection initiating almost entirely at calyx end of fruit. (12)

10b. Infection not restricted to calyx end. (11)

11a. Lesions 1-5 mm in diameter, purplish black in color associated with stomata, primarily on Mutsu (Crispin) variety. BLISTER SPOT (Pseudomonas syringae pv. papulans).

11b. Black, blotchy, sooty fungus growth on surface of fruit, most apparent near harvest. SOOTY BLOTCH (a complex of organisms including: Peltaster fructicola, Geastrumia polystigmatis, and Leptodontium elatus)

11c. Superficial fungus growth, showing black speckled pattern on fruit , most apparent near harvest. FLY SPECK (Zygophiala jamaicensis)

11d. Rot beginning as small, light brown, circular lesion. As lesions enlarge, they change to dark brown and form sunken or saucer-shaped depressions. Cream to salmon-colored spores may be produced on the surface of the lesion. Flesh beneath rot is "V"-shaped . BITTER ROT (Colletotrichum spp.)

11e. Fruit symptoms usually seen 4 to 6 weeks before harvest as small, slightly sunken brown spots that may be surrounded by a red halo. As the decay area expands, the core becomes rotten and eventually the entire fruit rots. Flesh is soft and watery under warm conditions. Red-skinned fruit may "bleach" during the decay process and become light brown. Also infects wood. WHITE ROT ("BOT" ROT) (Botryosphaeria dothidea)

12a. Infection may be restricted to calyx or may be actively rotting entire fruit. BLOSSOM END ROT (Sclerotinia sclerotiorum, Botryosphaeria obtusa, Botrytis cinerea)

12b. Infection initiating at open calyx and then extending inward to cause a black fungus core rot. Fruits ripen early and decay only obvious when fruit are cut in half. Important on varieties with open calyx such as Delicious and its Red Sports. MOLDY CORE (Alternaria alternata)

12c. No foliar lesions, usually fruit lesions which rarely sporulate , are dark green on the surface with necrotic tissues extending to the core. Particular problem on Delicious. Red cedar , the alternate host, may be observed near the orchard, but spores can travel great distances under the right conditions. QUINCE RUST (Gymnosporangium clavipes)

12d. Irregular, slightly sunken dark green lesions usually at the calyx end of immature fruit. Later, lesions turn dark red or purple on red areas of the fruit and remain dark green on green or yellow areas . Occasionally seen on varieties Jonathan, Golden Delicious, Stayman Winesap, Grimes Golden, and Rome Beauty. BROOKS SPOT (Mycosphaerella pomi)

13a. Yellow to orangish lesions apparent on leaves and sometimes on fruit. (14)

13b. Leaf or fruit lesions not orange in color. (16)

14a. May infect fruit and leaves . Most common apple rust . Red cedar , the alternate host, may be observed near the orchard. CEDAR APPLE RUST (Gymnosporangium juniperi-virginianae)

14b. Lesions only on leaves. (15)

15a. Found on McIntosh. Also attacks Hawthorn. HAWTHORN RUST (Gymnosporangium globosum)

15b. May develop on other varieties. CEDAR APPLE RUST (G. juniperi- virginianae)

16a. White powdery fungus growth on leaves and sometimes blossoms , causing distorted terminal growth. May cause net-like pattern of russetting on fruit. Fungus may appear on twigs of susceptible cultivars. POWDERY MILDEW (Podosphaera leucotricha).

16b. Foliage associated with a major branch or occasionally entire tree becomes silvery in appearance. SILVER LEAF (Stereum purpureum)

16c. Lesion on leaves and on fruit. Lesion olive to black in color, maybe necrotic. (17)

17a. Leaf and early fruit lesions olive to black and velvety in appearance. Maturing fruit cracked and/or misshapen and warty in appearance. APPLE SCAB (Venturia inaequalis)

17b. Leaf lesions frog-eyed in appearance , necrotic and may contain small black spherical structures (pycnidia). Fruit infections with extensive soft decay and rows of pycnidia sometimes apparent. BLACK ROT (Botryosphaeria obtusa)

18a. Milky ooze coming from cankers on bark in early spring. Beneath bark, wood is slimy in appearance. Cankers may have smooth or rough margins. Shoots adjacent to cankers may wilt and show ooze. FIRE BLIGHT (Erwinia amylovora)

18b. Black pycnidia on canker surface. Canker infection apparently initiated at large pruning cut or winter-injured site . BLACK ROT (Botryosphaeria obtusa)

18c. Infections initiated around lenticels, appearing as small circular spots or blisters. As canker expands, the area becomes depressed and watery exudate may appear. Later, black pycnidia may appear; at this stage the disease is indistinguishable from black rot. Outer bark of canker may slough and be papery, scaly, and orangish. WHITE ROT (Botryosphaeria dothidea)

18d. Wilting and death of new shoots in mid-summer. Pink to orange fungus sporulation apparent near previous seasons fruit scar or on older wood. Common on Rome Beauty, Twenty Ounce, and Ben Davis varieties. NECTRIA TWIG BLIGHT (Nectria cinnabarina)

18e. Target-shaped perennial cankers on limbs and/or trunk. NECTRIA CANKER

18f. Cankers on wood in weak orchards. Several wood rot fungi may invade weakened tissues. WINTER INJURY

KEY TO PEACH AND NECTARINE DISEASE IDENTIFICATION

1a. General growth and vigor of the tree is reduced. Trees stunted or weakened. Foliage wilted or off-color with early reddening and defoliation in the fall. No other obvious symptoms on tree. (2)

1b. Obvious leaf, blossom, or fruit infections, cankers, galls or leaf variegation patterns. (7)

2a. Decay is evident at the root/crown area. (3)

2b. Decay is not evident at the root/crown area. (4)

3a. Wood darkened and covered by living bark at its edges. Bark easily sloughs off crown area or southeast side of trunk. Larger roots may also be dead. WINTER INJURY

3b. Wood at canker is orange to brown in color, water-soaked and slimy. Canker, delimited by a definite margin of infection, sometimes extending into trunk or root area. Phytophthora isolated from margin of decay. PHYTOPHTHORA CROWN ROT (Phytophthora spp.)

3c. Bark at crown and roots easily sloughs off exposing dense white fungus growth with fan shaped distribution at cambium. Black shoestring-like strands (rhizomorphs) may be obvious on surface of bark and yellow-brown mushrooms may appear at base of tree in late summer or early fall. ARMILLARIA ROOT ROT (Armillaria mellea)

4a. Fibrous roots lacking or showing witches broom. Most common on light-textured soils. NEMATODE DAMAGE (Pratylenchus penetrans)

4b. Roots appear normal. (5)

5a. Bark easily sloughs off at crown area. (3)

5b. Bark missing at or below the soil line. Gnawing marks sometimes visible in wood. Callus formed in bark at margin of bare wood. RODENT DAMAGE

5c. Bark normal at crown area. (6)

5d. Bark abnormally thick and spongy, wood underneath has severely pitted . grooved, and indented texture. Leaves may have upward cupping , turning reddish purple, then dropping. PRUNUS STEM PITTING (Tomato Ring Spot Virus)

6a. Leaves wilted or browned on one or several scaffolds (flagging ). Rest of tree appears healthy. Dark streaks in sapwood of 2-3 year and older wood. Symptoms enhanced by water stress in mid-summer. VERTICILLIUM WILT (Verticillium albo-atrum)

6b. Flagging is not evident. Other above ground symptoms. (7)

7a. Distinct lesions or distortions of leaves. (8)

7b. Distinct lesions or blemishes on fruits. (11)

7c. Distinct lesions on leaves and fruits accompanied by twig cankers. (10)

7d. Cankers on twigs or branches only. (13)

7e. Blossom blight. (12)

7f. Small to large, warty appearing growths at crown or in roots. CROWN GALL (Agrobacterium tumefaciens) (Ohio State University).

8a. Distinct lesions or shot-holes visible on the leaves.(10)

8b. Leaves are cupped, swollen, distorted or in some way abnormally shaped. (9)

8c. Distinct white, powdery fungus growth on leaf surfaces. Leaves may drop prematurely, fail to elongate and unfold normally, while those on new shoots may become narrow, strap-like, and distorted. POWDERY MILDEW (Sphaerotheca pannosa)

9a. Leaves swollen and distorted along midrib early in the season, later turning red to purple, browning, and dropping from tree. Upper leaf surface becoming powdery-gray from fungal sporulation. Occasionally on fruit . PEACH LEAF CURL (Taphrina deformans)

9b. Leaves curled inward after several months. Water soaked spots turn red, necrotic and drop out giving leaves a tattered appearance. Localized areas or the entire canopy defoliates leaving foliage only at the tips. Choke cherry, the alternate host, may be seen near the orchard. Entire tree may show symptoms 2 to 3 years after the initial infection. X-DISEASE

9c. Leaves cupping upward, turning yellow, red, then dropping from localized areas of the canopy. PRUNUS STEM PITTING (Tomato Ring Spot Virus)

10a. Small, purple lesions surrounded by a green halo on leaves in the spring. Lesions become necrotic and fall out giving leaves a tattered appearance. Symptoms associated with deep, black depressions on fruit and cankering of twigs and branches. Occasionally a bare-branched or "leggy" condition resulting from buds and spurs killed by cankers. BACTERIAL CANKER (Pseudomonas syringae and P. mors-prunorum)

10b. Small, brown or black angular lesions surrounded by a light-green halo. Lesions most apparent at leaf tips. Later the lesions drop out (shotholing). Small circular, darkened, water-soaked lesions sometimes on twigs. Small circular lesions coalescing into cracks on developing fruit. The varieties Sunhigh, Afterglow, Collins, Merrill 49'er, RedGlobe, and Washington are very susceptible. BACTERIAL SPOT (Xanthomonas pruni)

10c. Leaves develop chlorotic spots, lines, and rings as they emerge. In severe cases chlorotic areas become necrotic and fall out, leaving the leaves shot-holed" or tattered. NECROTIC RING SPOT .

11a. White powdery areas on young peach or nectarine fruit. Hard, leathery dark lesions on older fruits. POWDERY MILDEW (Sphaerotheca pannosa or Podosphaera clandestina)

11b. Small, circular, dark green spots sometimes concentrated around stem-end of fruit. Small red lesions on twigs may be present, also. PEACH SCAB (Cladosporium carpophilum)

11c. Soft brown spots on maturing fruits that expand rapidly and produce tan powdery masses of spores. Infections from fruit may advance into wood causing small cankers . Fruit that is entirely rotted becomes "mummified" . Small (5 to 10 mm), brown, cup-shaped fungus fruiting bodies may form on mummies (that have overwintered on the ground) in the spring. BROWN ROT (Monilinia fructicola) or BOTRYTIS (Botrytis cinerea)

11d. Symptoms similar to brown rot but rot appears slightly darker, flesh may slip away from decaying flesh underneath. Visible fungal mycelium may be white and fluffy, looks like whiskers as the fungus sporulates. RHIZOPUS ROT (Rhizopus spp.)

12a. Gummy appearance of blighted blossoms . Powdery-gray mass of spores develop on diseased areas during warm wet conditions. Infection may continue to spread into twigs causing gummosis. BROWN ROT (Monilinia fructicola)

12b. Blossoms browned and withered during cool, wet weather. Brown lesions turn fuzzy gray from fungal sporulation. Disease not spread into twigs. BOTRYTIS (Botrytis cinerea)

12c.Blossoms wither, dry, and turn dark brown.infection may extend 1 or 2 inches into spur. No fungal sporulation or water-soaking on infected tissues is apparent. Freezing injury to blossoms favors Infection. BLOSSOM BLAST (Pseudomonas syringae)

13a. Perennial, elongated cankers surrounded by large, black, swollen rings of callus gumming . Canker associated with wounds, pruning stubs, peach tree borer, shaded-out twigs, or leaf scars. LEUCOSTOMA CANKER (Leucostoma cincta and L. persoonii).

13b. Flagging of current season's growth. Small, dark, oval cankers at buds, leaf scars, or bases of current season's twigs . Condition persists for only one year with symptoms most common in fall and spring. More frequent in warm regions. FUSICOCCUM CANKER (Phomopsis amygdali)

13c. Canker originating from blighted blossom. (12)

KEY TO CHERRY DISEASE IDENTIFICATION

1a. General growth and vigor of the tree is reduced. Trees stunted or weakened. Foliage wilted or off-color with early reddening and defoliation in the fall. No other obvious symptoms on tree. (10)

1b. Obvious leaf, blossom or fruit infections or distortions, cankers, galls, or leaf variegation patterns. (2)

2a. Small to large warty appearing growths at crown or root area, CROWN GALL (Agrobacterium tumefaciens) (Ohio State University)

2b. Small green, corky, elongated outgrowths (knots) on limbs. Knots turning black and woody after one season. Common on plum, occasionally found on sweet cherry, rarely on tart cherry. BLACK KNOT (Apiosporina morbosa = Dibotryon morbosum)

2c. No knots, tumors or galls. (3)

3a. Distinct lesions or distortions of leaves. (6)

3b. Distinct lesions or blemishes on fruits. (5)

3c. Fruits pointed, small, pale. (15)

3d. Blossom blight. (4)

3e. Cankers on twigs or branches only. (9)

4a. Gummy appearance of blighted blossoms. Powdery-gray masses of spores develop on diseased areas during warm wet conditions. Infection may continue to spread into twigs causing gummosis. BROWN ROT (Monilinia fructicola).

4b. Blossoms browned and withered during cool wet weather. Brown lesions turn fuzzy gray from fungal sporulation. Disease not spread into twigs. BOTRYTIS (Botrytis cinerea)