These can cause a number of secondary disease cycles depending on conditions. In the field, the disease is first observed on young seedlings. The pathogen does not persist if the host is incorporated into the soil. Host range tests have shown that C.g.m. is only pathogenic on species in the Malvaceae family. It produced small necrotic lesions on several ornamental Malvaceae and on the unrelated safflower.
Tolerance is based on a hypersensitive reaction.
In addition to rain splash, the pathogen is dispersed mechanically on livestock and machinery. It may also be spreading in western feed grain contaminated with in infected M. pusilla seed. Under maritime conditions, infected stem sections with lesions are an effective means of introducing the pathogen to new locations. Delaying application to meet these conditions enhances control. All stages of round-leaved mallow are susceptible.