Phoma rot of apple

The fungus survives on mummified fruit, bark, and plant debris left in the orchard. It produces pycnidia, which are small fruiting bodies containing spores that are the primary source of new infections.

Spores are dispersed by wind, rain splashes, and sometimes by insects. Infection usually takes place during the growing season, particularly when weather conditions are wet and humid.

Once the pathogen lands on a fruit surface, it enters through lenticels, wounds, or the stem end. The fungus then colonizes the internal tissues, secreting enzymes that lead to decay.

The lifecycle of Ectophoma pomi is well-adapted to cooler conditions, which makes it particularly problematic during the late autumn harvest and early storage phases.

Symptoms of Phoma rot typically appear as small, slightly sunken, circular spots on the apple skin. These lesions are usually brown to dark-brown in color.

As the infection progresses, black, pinhead-sized pycnidia appear in the center of the spots. These structures are a key characteristic for field diagnosis of this fungal infection.

The flesh beneath the spots becomes soft and spongy. If cut open, the decay often extends deep into the fruit towards the core, showing a distinct margin between infected and healthy tissue.

In advanced stages of the disease, the fruit may shrivel and take on a mummified appearance. A noticeable musty or fermented odor often accompanies the decay.

• Sunken, circular brown spots on the fruit surface.
• Presence of black pycnidia in the center of lesions.
• Soft, spongy texture of the internal flesh.
• Deep decay reaching the core of the fruit.

High humidity and moderate temperatures are the most critical environmental factors that promote the development and spread of Ectophoma pomi.

Poor orchard sanitation, such as leaving fallen or diseased fruit under trees, significantly increases the amount of inoculum available to infect healthy apples.

Dense tree canopies that limit air circulation create moisture traps, allowing the pathogen to thrive and infect developing fruits more easily.

Physical injuries to the skin of the fruit, caused by insects, hail, or rough handling during harvest, significantly increase the risk of infection.

Improper post-harvest handling, including storing apples in facilities with inadequate cooling, provides the ideal environment for the fungus to spread rapidly among stored fruit.

The primary damage caused by Phoma rot is the destruction of fruit quality during storage, which can lead to severe financial losses for producers and retailers.

Infected apples become completely unmarketable due to the rapid development of soft rot and the aesthetically unpleasing presence of lesions and pycnidia.

Since the disease can spread by contact in storage crates, a single infected apple can lead to the loss of an entire batch if not caught during the sorting process.

The inability to store the harvest for long periods forces growers to sell their produce prematurely, often at lower market prices.

Phoma rot also complicates export processes, as strict quality controls often result in the rejection of infected fruit shipments.

Cultural control is essential: practice proper tree pruning to ensure good light penetration and air movement, which keeps the canopy dry and inhibits fungal growth.

Orchard sanitation is critical; collect and remove all mummified fruit and debris from the orchard floor to reduce the overwintering population of the fungus.

Applying fungicides according to local recommendations during the growing season can help reduce spore levels and prevent initial fruit infections.

Ensure that storage facilities are thoroughly cleaned and disinfected before the new harvest is moved in to prevent cross-contamination.

Careful sorting and grading before storage are mandatory to remove any fruits showing even minor signs of injury or spotting, thereby protecting the overall harvest quality.