Fungal diseases
| | Alternaria fruit rot | Alternaria spp. |
| Anthracnose canker and bull's-eye rot | Pezicula malicorticus
Cryptosporiopsis curvispora [anamorph] |
| Armillaria root rot (shoestring root rot) | Armillaria mellea
Rhizomorpha subcorticalis [anamorph] |
| Bitter rot | Glomerella cingulata
Colletotrichum gloeosporioides [anamorph] |
| Black rot, leaf spot and canker | Botryosphaeria obtusa
Sphaeropsis malorum [anamorph] |
| Black spot (of Japanese pear) | Alternaria alternata |
| Blister canker | Helminthosporium papulosum |
| Blister disease | Coniothecium chomatosporum |
| Blue mold rot | Penicillium spp.
Penicillium expansum |
| Botrytis spur and blossom blight | Botrytis cinerea
Botryotinia fuckeliana [teleomorph] |
| Brown rot | Monilinia fructicola
Monilinia laxa |
| Cladosporium fruit rot | Cladosporium herbarum
Mycosphaerella tassiana [teleomorph] |
Clitocybe root rot (mushroom root rot)
| Armillaria tabescens
{{=}} Clitocybe tabescens |
| Coprinus rot | Coprinopsis psychromorbida |
| Dematophora root rot (Rosellinia root rot) | Rosellinia necatrix
Dematophora necatrix [anamorph] |
| Diplodia canker | Botryosphaeria stevensii
{{=}} Physalospora malorum
Diplodia mutila [anamorph] |
| Elsinoe leaf and fruit spot | Elsinoe piri
Sphaceloma pirinum [anamorph] |
| European canker | Nectria galligena
Cylindrocarpon heteronemum [anamorph] |
| Fabraea leaf and fruit spot | Diplocarpon mespili
{{=}} Fabraea maculata
Entomosporium mespili [anamorph] |
| Fly speck | Schizothyrium pomi
Zygophiala jamaicensis [anamorph] |
| Gibberella canker | Gibberella baccata
Fusarium lateritium [anamorph] |
| Gray mold rot | Botrytis cinerea |
| Late leaf spot | Cercospora minima |
| Mucor fruit rot | Mucor spp.
Mucor piriformis |
| Mycosphaerella leaf spot (ashy leaf spot and fruit spot) | Mycosphaerella pyri
{{=}} Mycosphaerella sentina
Septoria pyricola [anamorph] |
| Nectria twig blight (coral spot) | Nectria cinnabarina
Tubercularia vulgaris [anamorph] |
| Pear scab | Venturia pyrina
Fusicladium pyrorum [anamorph] |
| Perennial canker | Neofabraea perennans
Cryptosporiopsis perennans [anamorph] |
| Phyllosticta leaf spot | Phyllosticta sp. |
| Phytophthora crown and root rot (sprinkler rot) | Phytophthora cactorum |
| Pink mold rot | Trichothecium roseum
{{=}} Cephalothecium roseum |
| Powdery mildew | Podosphaera leucotricha |
| Pythium dieback | Pythium spp. |
| Rhizopus rot | Rhizopus stolonifer |
| Rust, American hawthorne | Gymnosporangium globosum |
| Rust, Kern's pear | Gymnosporangium kernianum |
| Rust, Pacific Coast pear | Gymnosporangium libocedri |
| Rust, pear trellis (European pear rust) | Gymnosporangium fuscum |
| Rust, Rocky Mountain pear | Gymnosporangium nelsonii |
| Side rot | Phialophora malorum |
| Silver leaf | Chondrostereum purpureum |
| Sooty blotch | Gloeodes pomigena |
| Thread blight (Hypochnus leaf blight) | Corticium stevensii
{{=}} Pellicularia koleroga
{{=}} Hypochnus ochroleucus |
| Valsa canker | Valsa ceratosperma
Cytospora sacculus [anamorph] |
| Wood rot | Trametes versicolor
and various basidiomycetes |
| Xylaria root rot | Xylaria spp. |
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