Above-ground symptoms often mimic nutrient deficiencies, such as yellowing (chlorosis) and stunted growth, causing gardeners to over-fertilize, which only increases stress on the plant. The most distinct sign is a dramatic, firm, blackening of the roots—specifically caused by the buildup of dark chlamydospores. How the Fungus Spreads Black Root Rot - UC IPM
Pansy, Viola, Calibrachoa (Million Bells), Vinca, Petunia, Poinsettia, and Phlox. black root rot fungus
Black root rot thrives in cool, wet, and often alkaline (higher pH) soil conditions. It is a versatile pathogen, affecting a wide range of plants, including: Above-ground symptoms often mimic nutrient deficiencies
Hollies (especially Ilex crenata ), Boxwood, and Citrus. Crops: Tobacco, Cotton, Carrots, and Lettuce. causing gardeners to over-fertilize
The Silent Killer: Understanding and Managing Black Root Rot