Willow bark

The activity of willow bark-based products is based on a high content of natural phenolic compounds, primarily salicin. Upon contact with the plant surface, salicin is metabolized into salicylic acid.

Salicylic acid acts as a key signaling hormone that activates the systemic acquired resistance (SAR) of plants. This puts the plant's defense systems in a state of high alert against environmental stressors.

The mechanism of action focuses on strengthening cell walls, which hinders the penetration of pathogenic microorganisms. The agent does not kill the pathogen directly but renders the plant invulnerable to infection.

In addition to protective functions, components of willow bark stimulate root formation and vegetative growth. This occurs due to the influence of natural auxin-like substances present in the bark structure.

The natural composition of the extracts ensures overall rhizospheric health by suppressing the development of certain soil-borne pathogens through the modulation of pH balance and microbial activity.

Willow bark is primarily used to protect vegetable, fruit, and ornamental crops from a wide range of fungal diseases, including powdery mildew, late blight, and scab.

When used as a growth stimulant, the main goal is to increase seed germination rates and improve seedling survival after transplantation. The extract significantly accelerates the regeneration of damaged tissues.

Willow bark extracts are often included in protection programs against leaf spots caused by fungi of the Septoria and Alternaria genera. It also helps reduce rot infection in crops during storage.

There is a positive effect observed in preventing rust on cereals and floral crops. This allows for a reduction in the number of applications of conventional synthetic fungicides.

The agent is effective in combating pathogens that cause seedling damping-off by activating the plant's internal defense mechanisms during critical periods of development.

Working solutions are prepared by steeping ground willow bark in water. The standard concentration ranges from 50 to 100 grams of raw material per liter of water, followed by dilution before use.

Applications are recommended to be performed preventively, starting from the active growth phase up to flowering. The interval between spraying is typically 7 to 14 days, depending on environmental conditions.

For pre-sowing treatment, seeds should be soaked for 6 to 12 hours before planting. This stimulates germination energy and provides initial protection against soil-borne infections.

When applying as a root drench, it is crucial to use freshly prepared infusions to preserve the biological activity of the salicylates. Solutions should not be stored for long and must be used within 24 hours.

Application rates depend on the method of administration: ranging from 200–300 liters per hectare for foliar spraying to intensive substrate drenching in greenhouse conditions.

A major limitation is the dependence of efficacy on weather conditions. Heavy rain can wash away active substances, requiring re-application or the use of surfactants to improve adherence.

Mixing willow bark extracts with highly alkaline preparations, such as Bordeaux mixture, should be avoided, as high pH levels can neutralize the action of organic acids.

Willow bark is not a systemic insecticide or a highly effective curative fungicide for severe infestations. It serves as an excellent preventive measure but does not replace radical chemical protection during epidemics.

When handling concentrated infusions, personal protective equipment should be used. Despite their natural origin, high concentrations of phenolic compounds can cause irritation to skin and mucous membranes.

Dried bark should be stored in a dry, ventilated area away from direct sunlight to prevent the degradation of active substances sensitive to ultraviolet radiation.