Article prepared by the technical team of Avium SpA.

As the first signs of proper dormancy in cherry trees begin to appear, under favorable climatic conditions, preparations should commence for the phytosanitary management during the winter dormancy period.

The autumn-winter period is critical because deciduous trees undergo various physiological processes, primarily expressed as leaf abscission, a key process where senescence occurs followed by leaf drop.

Factors such as decreasing ambient temperatures, increased relative humidity, shorter photoperiods, and cultural practices—such as the cessation of post-harvest nutrition until the end of February and gradual reduction of irrigation until the end of March—promote the accumulation of growth inhibitors, halting growth and facilitating leaf drop, marking the beginning of dormancy.

This phase is characterized by a drastic reduction in metabolic activity and is manifested at the end of the post-harvest period, accompanied by practices during the transition phase aimed at acclimatizing or “hardening” the plant for winter dormancy.

From a health perspective, before leaf drop, it is the optimal time for sanitary pruning, as infected material (sick and dead plants and branches) can be visualized during this phase. Systematic removal of this material is fundamental to reducing infection sources and eradicating pathogens. The use of healing pastes with fungicidal action is crucial due to the significant interventions performed on the plant.

During the leaf drop phase, adequate phytosanitary control is important as wounds caused by abscission can be considered “entry points” for diseases. The wounds exposed during the leaf drop process become focal points for pathogen entry. This risk should be mitigated by implementing a preventive program aimed at reducing the incidence of diseases such as bacterial canker (Pseudomonas syringae pv. syringae) and various fungi that cause wood diseases, which often act silently and are the primary agents of sudden plant death in spring.

After leaf drop, a preventive approach usually involves applications of copper and/or long residual effect fungicides, which should be repeated under certain conditions, such as frost events, but not necessarily due to precipitation.

Another important operation is winter pruning, where it is essential to consider that cuts with a diameter greater than 8-10 mm must be properly treated, as the exposed area heals slowly and with difficulty. Additionally, the use of biological fungicides is an alternative to cover all cuts with diameters less than 8 mm, which are practically very difficult to treat completely.

“The application of copper-based products, primarily targeting bacteria, has become a standard practice during the autumn and winter stages, being especially effective in the initial phase of the cycle, where it is used to cover natural lesions caused by leaf drop. It is recommended to perform two to three applications as the defoliation process progresses. Subsequently, a program of systematic applications should be established, with intervals of 25 to 30 days, considering the specific climatic conditions of each microzone in central and southern Chile. This program should conclude at the phenological state of swollen buds, marking the last application of the winter program and the first of the spring program,” stated Avium’s Technical Director, Carlos Tapia.

To implement effective prevention and control methods against infections caused by wood fungi, studies have been conducted to evaluate the efficacy of available chemical and biological products on the market, both in paint formulations and sprayable products.

Over time, solutions have emerged that not only limit the spread of pathogens but also ensure efficient and sustainable control. The use of elicitors with SAR (Systemic Acquired Resistance) effect stimulates the immune response of the plant or microorganisms (Bacillus, Trichoderma, etc.) that compete with diseases and are increasingly being utilized.

It is crucial to minimize infection risks during the autumn-winter period by implementing an adequate phytosanitary management program that ensures the health of both developing and producing orchards. This approach will maintain plant health and ensure that the orchard arrives in optimal condition for the new productive season.