|
Can Soil Amendments Reduce Disease Severity in Trees
(Part 2)
From Roots to Canopy: Boosting Tree Defenses Against Pests and Diseases
Dr. Glynn Percival
Senior Arboricultural Researcher
Bartlett Tree Research Laboratory, Charlotte, NC
*For Part 1 of this article, see our January 2025 issue.
Single species mulch (Salix spp)
Research has shown that mulches are an effective cultural control method for suppressing the development of various plant diseases (see photograph below). When mulch is applied to the soil surface, it increases microbial and fungal populations, which enhances enzymatic activity, including cellulase and laminarinase, facilitating mulch decomposition. The cellulose microfibrils in the cell walls of Phytophthora are particularly susceptible to enzymatic degradation, especially by cellulases in the mulch litter layers, leading to cell wall lysis and a subsequent reduction in the severity of Phytophthora infections.
There is limited research on the efficacy of mulches derived from a single tree species. Notably, willow (Salix) mulch, which is naturally high in salicylic acid, a potent activator of plant defense mechanisms, has shown promise. The application of salicylic acid to plants has been demonstrated to confer resistance against several plant pathogens, including early blight of potato (Alternaria solani), powdery mildew (Erysiphe cichoracearum), tobacco mosaic virus, fire blight (Erwinia amylovora), Sclerotinia sclerotiorum, and Phytophthora palmivora.
Conclusions
Current research indicates that the soil amendments discussed herein provide a viable method for managing a wide range of economically significant foliar and root diseases in urban trees. The materials employed, such as chitin, biochar, and wood chip mulch, are primarily industrial by-products or waste, offering an environmentally sustainable approach to pest and disease management. It is crucial to note that these amendments should not be used in isolation for pest and disease control. Effective management should also focus on enhancing tree vitality and minimizing all forms of stress whenever possible. Continuous aftercare is essential for successful pest and disease management.
| 
