Disease	Symptoms	Pathogen/Cause	Management
Fire Blight	Infected flowers are killed and often remain attached throuthout the season. The ends of twigs and branches become brown or black and may curl over into a shepherd's crook shape. Dead leaves may remain attached to the tree. Branches will be killed as slightly sunken cankers enlarge into larger branches and even into the main trunk. Cankers formed the previous season may ooze a cloudy liquid during wet spring weather.	Erwinia amylovora	During dormancy when the weather is dry, prune infected branches, cutting at least 4 inches below the base of the canker. Disinfest pruning tools frequently. During the growing season, make pruning cuts at least 12 inches below the base of the canker. Fertilize carefully to avoid promoting excessive succulent growth. Remove root suckers and water sprouts while they are small. Grow resistant cultivars (see below). Remove nearby unwanted plants that are susceptible to fire blight.
Frogeye Leaf Spot	Distinct, brown, circular spots form after leaves expand. Some spots enlarge along the margin of thedead area giving it a lobed shape. Older areas of the spot turn gray while the rest of the spot is brown, giving it a concentric pattern of color. In severe infections, leaves yellow and fall prematurely.	Botryosphaeria obtusa	In the nursery, apply a fungicide to protect new leaves.
Scab	Dull, olive-green, velvety fungal growth develops on the surface of leaves and petioles in the spring. Leaves yellow and fall premature.giving the tree a thin, bare appearance by mid-season. Infected fruit have circular, rough spots on their surface.	Venturia inaequalis	Grow resistant cultivars (see below). Rake and destroy fallen leaves and fruit. Apply a mix of propiconazole + chlorothalonil at early pink and again 3 weeks later.
Cedar-Apple, Cedar-Hawthorn, and Cedar-Quince Rusts	Bright yellow or yellow-orange spots form on leaves. On the upper surface of the leaf spot, small black fungal fruiting structures form. Later on the underside of the infected leaves, clusters of cup-shaped structures with fringed edges can be observed. Similar structures may appear on fruit.	Gymnosporangium juniperi-virginiana (cedar-apple), G. clavipes (cedar-quince), G. globosum (cedar-hawthorn)	Where the disease seldom occurs or few leaves are infected, no control is necessary. Otherwise, remove nearby junipers. Or, remove the galls from juniper branches during dormancy. Apply chlorothalonil, fenarimol, myclobutanil, propiconazole, triadimefon, or mancozeb when flower buds can be seen and again at petal fall.

Fire blight-resistant crabapples:
Adams, Adams Dwarf, Callaway, David, Dolgo, Harvest Gold, Indian Summer, Jewelberry, Liset, Pink Princess, Pink Spires, Profusion, Red Baron, Robinson Dwarf, Selkirk, Sentinel, Spring Snow Dwarf, and Velvet Pillars

Scab-resistant crabapples:
Adams, Baskatong, Brandywine, Callaway, Coral Burst, David, Dolgo, Donald Wyman, Malus floribunda, Henry Kohankie, Henningi, Jewelberry, Ormiston Roy, Professor Sprenger, Malus seiboldi var. zumi cultivar Calocarpa, Silver Moon, Sugartyme, Malus tschonoskii, Weeping Candy Apple, White Angel, and White Cascade have been observed in many locations to have only slight to moderate scab infections.