Oil blotch of peach

Oil blotch is a fungal disease that affects stone fruits, particularly peach trees. The pathogen thrives in high-humidity environments where poor air circulation within the canopy facilitates the rapid spread of spores throughout the orchard, causing significant physiological distress to the host plant.

The primary host for this disease is the peach (Prunus persica). The pathogen survives the winter in dormant buds, bark crevices, or infected fallen leaves, emerging in early spring when warm, moist weather conditions align with the susceptible stages of leaf development.

Symptoms appear as translucent, oily-looking spots on the leaf blades. These lesions are often irregular in shape and may exhibit a greasy sheen, differentiating them from other common spot diseases. As the infection progresses, the spots may turn brown or necrotic, leading to leaf yellowing and eventual shedding.

The damage caused by oil blotch is primarily related to the reduction of photosynthetic capacity. Excessive leaf loss weakens the tree, reduces fruit size and sugar content, and may prevent the tree from properly hardening off before the onset of winter frosts, resulting in long-term yield decline.

Control measures rely heavily on integrated pest management (IPM). This includes strict sanitation, such as removing fallen leaves where the fungus overwinters, and the application of protective fungicides. Proper orchard management, including pruning for airflow and balanced nitrogen fertilization, is essential to mitigate the risk.

• Sanitary pruning of infected branches.
• Copper-based fungicide applications in early spring.
• Regular removal of debris from the orchard floor.
• Monitoring weather patterns to time fungicide sprays.