These spores rise into the air and land on the surface of a susceptible tree, where they germinate and form a germ tube that can directly penetrate the plant's waxy cuticle.

A fungal mycelium forms between the cuticle and underlying epidermal tissue, developing asexually the conidia, that germinate on fresh areas of the host tree, which in turn produce another generation of conidial spores.

V. inaequalis overwinters mostly as immature perithecia, where sexual reproduction takes place, producing a new generation of ascospores that are released the following spring.

Foliar symptoms begin to occur in the early spring around budbreak and mainly present as light green lesions that progress to an olive-brown color with a velvety texture due to conidia formation as time passes.

[11]  While the disease can cause total crop loss in optimal conditions without management, the main economic impact is due to the reduction in both size and marketable quality of the fruit.

This issue is further compounded by the fact that apple cultivars with a high market share, Pink Lady for example, are susceptible to the pathogen while more resistant varieties are less well known or desired by consumers.

Considering most of these are commercially used as ornamental species, flowering crab apples for example, the importance of the pathogen shifts to be a more aesthetic nuisance.

The fungi's mechanistic similarity to obligate parasites while still being able to be cultured in media has led to its repeated use in the study of the genes related to pathogenicity.

[10] Protection from initial inoculation, either via sexual ascospores or asexual conidia, with fungicide is the main form of pathogen management.

Orchard design and planting patterns focusing on increased aeration are important in ensuring that susceptible tissues dry prior to initial infection.

[14] Primary infection is mainly caused by the ascospores that overwinter in the fallen debris and the density of these spores in the spring is directly related to the speed and intensity of an apple scab outbreak.

[12]  More recently, biofungicidal methods of control have emerged in studies with some promise being shown by the organism Microsphaeropsis ochracea in reduction of initial ascospore inoculum of up to 70–80 percent.