| Disease or defect | Source of pathogen or disorder | Diagnosis and location on/in tuber | Spread within storage1 | Remarks | ||
| Soil | Seed | Other | ||||
| Common scab | X | X | External, general | No | ||
| Powdery scab | X | X | External, general | Yes | ||
| Rhizoctonia | X | X | External, general, must wash | No | ||
| Silver scurf | X | X | External, general, must wash | Yes | ||
| Bacterial soft rot | X | X | X | External, general; internal, general | Yes | Other sources are from cull piles and irrigation water |
| Blackleg | X | X | External, stem end; cut internal, stem end, and longitudinal | No | ||
| Early blight | X | X | External, general; internal, make shallow cuts through lesions | Yes | ||
| Freezing and chilling | X | External; cut internal, stem end and cross section | No | |||
| Fusarium rot | X | X | External, general; internal, cut through lesions | No | ||
| Late blight | X | X | External, general; internal, cut through lesions | Yes | Other sources include cull piles and volunteers | |
| Leak | X | External, general; internal, cut aroundwounds and stem end | No | |||
| Mechanical injury | X | External, general; internal, cut through damaged area | No | |||
| Pink rot | X | External, stem end, eyes, lenticels; cut internal, turns pink | Yes | |||
| Ring rot | X | X | External skin cracks; cut internal, near stem end | No | Other sources of inoculum include volunteers, equipment and containers | |
| Root knot | X | X | External, general; internal, cut tangential | No | ||
| Black heart | X | X | Cut internal, longitudinal | No | Caused by lack of oxygen under certain field conditions, in storage, and in transit | |
| Black spot | X | Cut internal, stem end half or on shoulder | No | Deep piles contribute to problem | ||
| Fusarium wilt | X | X | Cut internal, through stem end, only in xylem | No | ||
| Leafroll | X | X | Cut interna, cross section | No | Insect transmissioon from infected plants in cull piles and volunteers | |
| Verticillium wilt | X | X | Cut internal, extends through vascular ring | No | ||
1Refers to tuber-to-tuber spread. Some of the diseases and disorders will progress within affected tubers in storeage, but will not spread to healthy tubers.