Propiconazole

Propiconazole is a systemic fungicide belonging to the triazole chemical class. It works by inhibiting ergosterol biosynthesis, a critical component of fungal cell membranes, effectively stopping fungal growth. In tree care, it is one of the most important fungicides for managing vascular diseases and has become a standard treatment for protecting elms against Dutch elm disease.

The most common tree care application of propiconazole is preventive trunk injection to protect high-value elms from Dutch elm disease. When injected into the vascular system before infection, it can provide two to three years of protection. It is also used for managing oak wilt, sycamore anthracnose, crabapple scab, and various other fungal diseases. The product is typically delivered through macro-injection systems that introduce the fungicide directly into the sapwood.

Treatment timing is critical for propiconazole effectiveness. For Dutch elm disease prevention, injections are typically performed in spring when the tree is actively transpiring and can distribute the product throughout the canopy. The treatment must be performed before the tree becomes infected, as propiconazole is far more effective as a preventive than a curative treatment. Retreatment is needed every two to three years to maintain protection.