What environmental conditions are best for the occurrence of blackleg disease?

Blackleg disease, primarily caused by the pathogen Phoma lingam, is most prevalent under cool, moist conditions. This environment is conducive to the disease's development because the fungus thrives where temperatures are moderate, typically between 10-20 degrees Celsius (50-68 degrees Fahrenheit), and where humidity levels are elevated. The moisture helps the pathogen in spreading and infection, allowing it to penetrate the plant tissues more easily.

In contrast, warm, wet conditions, cool, dry conditions, and warm, dry conditions do not support the same level of pathogen activity. While excess moisture is essential, high temperatures can inhibit the fungus's growth and lessen disease severity. Similarly, cool, dry environments do not provide the necessary moisture for the pathogen to propagate effectively. Warm and dry conditions further limit the disease's potential by creating less favorable conditions for infection and growth. Thus, the combination of cool air and moist soil creates an optimal scenario for the occurrence of blackleg disease.