Conidia on the mycelial mat gives it a distinct powdery appearance. Stems, flower pedicels, and fruits as well as leaves can become infected. Although leaves of all ages are considered susceptible, infection is largely confined to the older leaves approaching senescence. Seedling plants are especially susceptible to attack and may be seriously affected. Defoliation, stem and fruit lesions on young plants may lead to measureable yield losses.
Seedlings grown in greenhouses are especially susceptible, often killing the apical portions.
Mycelium of O. caricae is hyaline and septate. Haustoria develop in the host's epidermal cells to obtain nourishment for the pathogen. The conidial stage is the only form present in Hawaii and other tropical areas. The sexual stage has never been observed. Although control measures are generally not needed applications of wettable sulfur, sulfur dust, or lime sulfur have proved helpful in controlling this disease.