Decline as a Disease Category: Is It Helpful?

Many, but not all, forest pathologists use decline to describe forest tree diseases of complex etiology. We contend that this distinction from abiotic or biotic diseases is completely arbitrary, has caused undue confusion, and provides no practical insights for forest managers. All diseases are complex and can be characterized within the conceptual framework of the disease triangle. Why do we use a simple label (decline) to describe disease situations of complex abiotic and biotic origin when we need to know which damaging agents are present, whether the environment is conducive for disease progression, and host susceptibility over time to understand the origins and management of disease? We propose that forest pathologists discontinue the use of decline as a distinct category of disease. Furthermore, we suggest that new diseases should be named based on the affected host, characteristic symptom, and, once known, major determinant. We believe that clearer communication in describing complex diseases is a prerequisite to finding effective management options.