Bitter Rot

Identifiable traits

Its primary symptoms appear during the spring as small grey or brown flecks on young fruits.

As soon as summer starts, these flecks have developed into small, sunken, brown lesions, sometimes surrounded by a conspicuous red halo. As soon as the conditions become favourable to them, a few of these lesions enlarge further and show small, black or dark brown dots on their middle. As time passes, the brown, watery rot expands from surface to the core of the fruit, forming a V-shaped pattern (cylindrical rot pattern around the core are typical of another disease of apple, bot rot). This decomposes the decaying apple and dries up and usually remains hanging on the branch, forming a so-called mummified fruit. Infections are characterized by small purple flecks that later enlarge to irregular necrotic areas of the leaves. Leaves that are affected severely turn yellow and eventually shed. The contagion of the disease to shoots will compromised flowering the following season. All varieties of apple are susceptible to bitter rot.

Inducing factors

The symptoms on leaves and fruit are caused by two different sexual stages of the same pathogen. The spots on leaves and fruit are the results of the colonization of the tissues by the sexual form Glomorella cingulate. Colletotrichum gloeosporiodes is the asexual form and is the causal agent for the fruit lesions later in the season. Infected wood and mummified fruits are the overwintering sites of the fungus. During the spring, it starts growing and produces spores that are released by rain splashes and dispersed by wind. As temperature elevates

 (25˚ C) and prolonged periods of leaf wetting favoured the life cycle of the fungus and infection development, but are more common in the latter half of the season. Epidemic proportion and immense loss can be reached during prolonged periods of wet warm weather during fruit growth.