This article is a list of diseases of hazelnut (Corylus avellana & Corylus spp.).
Bacterial diseases
| Bacterial diseases | |
|---|---|
| Bacterial blight | Xanthomonas arboricola pv. corylina | 
| Bacterial canker | Pseudomonas syringae pv avellanae | 
| Crown gall | Agrobacterium tumefaciens | 
Fungal diseases
| Fungal diseases | |
|---|---|
| Anthracnose | 
 Piggotia coryli   | 
| Armillaria root disease | Armillaria spp. | 
| Borro sec | Cryptosporiopsis tarraconensis | 
| Cytospora canker | Cytospora spp. | 
| Eastern filbert blight | Anisogramma anomala | 
| Kernel molds | 
 Mycosphaerella punctiformis [teleomorph]   | 
| Kernel spot | Nematospora coryli | 
| Leaf blister | Taphrina coryli | 
| Leaf spots | 
 Anguillosporella vermiformis   | 
| Nectria canker | Nectria ditissima | 
| Texas root rot | Phymatotrichopsis omnivora | 
| Powdery mildew | Microsphaera coryli  Microsphaera ellisii   | 
| Rust | Pucciniastrum coryli | 
Viral diseases
| Viral diseases | |
|---|---|
| Hazelnut mosaic | genus Ilarvirus, Apple mosaic virus (ApMV)  genus Ilarvirus, Prunus necrotic ringspot virus (PNRSV)   | 
Phytoplasmal and spiroplasmal diseases
| Phytoplasmal and spiroplasmal diseases | |
|---|---|
| Filbert Stunt | unknown, suspect a phytoplasma | 
| Hazelnut Yellows | phytoplasma | 
Miscellaneous diseases and disorders
| Miscellaneous diseases and disorders | |
|---|---|
| Blanks | empty nut shells, cause unknown | 
| Brown Stain | brown liquefied portions of shell and kernel, cause unknown | 
| Catkin Blast | deformed catkins, cause unknown | 
| Sun Scald | high temperature | 
| Wet Feet | saturated soil conditions for extended periods. |