Disease	Symptoms	Pathogen/Cause	Management
Fire Blight	Flower clusters are killed and turn dark brown to black. Dead leaves and aborted flower parts remain on the tree. Slightly sunken cankers are seen where the dead wood meets the live. In the spring, slime may ooze from the canker if the weather is warm and wet. No fungal fruiting structures are found in the canker.	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. Use fertilization practices that do not promote excessive succulent growth. Remove root suckers and water sprouts while they are small. Remove unwanted plants that are susceptible to the disease from near cultivated plants. Plant resistant hawthorns such as Crataegus arnoldiana, C. coccinea, C. crus-galli, C. douglasii, C. phaenopyrum, C. prunifolia, C. puntata "Ohio Pioneer," or C. viridis "Winter King."
Cedar-Hawthorn Rust	Orange-yellow spots form on leaves and severely affected leaves fall prematurely. Green fruit is deformed.	Gymnosporangium globosum	Plant resistant hawthorns including cockspur thorn, yellow fruited thorn, Crataegus intricata, and Crataegus pruinosa. Apply azoxystrobin, mancozeb, chlorothalonil, mancozeb + thiophanate methyl, myclobutanil, or triadimefon at 10 day intervals beginning just as flower bud break occurs. Do not plant close to junipers.
Cedar-Quince Rust	Petioles, twigs, and thorns swell and become distorted. Fruit is covered with spore horns during the summer. Orange-yellow spots form on leaves that, if severely affected, fall prematurely.	Gymnosporangium clavipes	Apply azoxystrobin, chlorothalonil, mancozeb + thiophanate methyl, mancozeb, myclobutanil, or tridimefon at 10-day intervals beginning just as flower bud break occurs. Do not plant close to junipers.
Leaf Blight and Fruit Rot	Leaves wilt, turn brown, and die in the spring. Flower clusters die. Fruits turn brown, mummify, and fall.	Monilinia johnsonii	If possible, remove and destroy fallen mummified fruits before bud break occurs.
Leaf Spot	Many small reddish-brown to gray leaf spots develop, sometimes with dark-brown borders. Spots may be so numerous that they merge. Infected leaves yellow quickly and fall by August. On twigs, slightly raised, brown, irregular spots form. English hawthorn (Crataegus oxycantha) and Pauls Scarlet (Crataegus oxycantha pauli) are very susceptible.	Diplocarpon mespili (Entomosporium, asexual stage)	Rake and destroy fallen leaves. Apply azoxystrobin, myclobutanil, chlorothalonil or mancozeb + thiophanate methyl during bud break and at 10-day intervals during wet weather Two or three applications may be sufficient. Cease spraying if the weather dries.

Fungicides mentioned above:

COMMON NAME	TRADE NAME
azoxystrobin	Heritage
chlorothalonil	Daconil 2787
copper	Kocide, Nu-Cop, Phyton 27
copper + mancozeb	Junction
iprodione	Chipco 26019
mancozeb	Dithane, Protect T/O
mancozeb + thiophanate methyl	Duosan, Zyban
myclobutanil	Eagle, Systhane
thiophanate methyl	Clearys 3336
triadimefon	Bayleton