Neofusicoccum (fungal canker pathogen)

Neofusicoccum is a fungal plant pathogen belonging to the Botryosphaeriaceae family. While not a cactus clone itself, it is a significant pathogen affecting *Trichocereus* species, most notably the Predominant Cultivar (PC) *Trichocereus pachanoi*. The host plants typically feature 5 to 8 rounded ribs, a light green to glaucous blue-green epidermis, and short, upturned yellowish spines arising from white felted areoles. When infected with Neofusicoccum, the host's epidermis develops dark, sunken fungal cankers and necrotic lesions that compromise the plant's aesthetic and structural integrity. The pathogen is slow-moving and rarely transfers to scions or new pups, though transmission remains possible if left unchecked.

The identification of Neofusicoccum (often spelled “Neofussicoccum” in community discussions) within *Trichocereus* collections was highlighted by community expert Gee Bee in early 2026. The pathogen is known in broader agriculture, but its specific impact on cultivated *Trichocereus* stands, particularly PC during winter, has been documented through community observations. The original environmental source or vector of the pathogen in these collections remains undocumented.

To manage and suppress Neofusicoccum infections, growers must employ targeted chemical controls, as standard organic treatments like sulfur may not be fully effective.

• Fungicide Rotation: A combination of Mancozeb (a broad-spectrum contact fungicide) and Thiophanate-methyl (a systemic fungicide) is highly recommended. Rotating these two active ingredients provides full control and suppression of the pathogen.
• Products & Sourcing: Thiophanate-methyl is commercially available under the brand name TM 4.5 (manufactured by Quali-Pro). Because these commercial-grade fungicides may face shipping restrictions on major platforms like Amazon depending on state regulations, hobbyists often source smaller, repackaged portions of Mancozeb on eBay.
• Application: It is recommended to use a “rain guard” formulation of the fungicide and mix it with a surfactant to ensure the spray adheres to the slick, waxy cuticle of the cactus.
• General T. pachanoi Care: Keep plants dry and well-ventilated during cold winter months, as damp, cold conditions correlate with symptom expression.