Convallaria sp. (Lily-of-the-valley) is subject to several diseases. Anthracnose, leaf spot, leaf blotch and crown rot are the main diseases. Anthracnose causes lesions that are often oval in shape and dark brown in color with purplish margins. These spots may fall out, exposing the veins. This disease is not usually fatal but does weaken the plant. The following year, the number of flowers is often reduced. Wet conditions promote infection and spread of the disease. Leaf spot causes brown spots with purplish-brown margins. The spots are small and more or less round. An insect problem that occurs occasionally on Lily-of-the-valley is black vine weevil. This insect chews notches in the edge of the leaf margins (about the size of a paper punch).
Written by James Schuster, Extension Educator, Horticulture, and reviewed by Bruce Paulsrud, Extension Specialist, Plant Pathology and Phil Nixon, Extension Entomologist, University of Illinois at Urbana-Champaign.