Urtica spp.

Extracts and infusions from plants of the Urtica spp. group are classified as plant-based biopreparations widely used in ecologically clean and organic farming. The active ingredients include organic acids, phytoncides, flavonoids, and high nitrogen content, which, upon contact with pathogens or pests, cause suppression of their vital functions.

The mechanism of action of nettle infusion lies in the systemic improvement of cultural plants' immunity. When sprayed, the active components strengthen the epidermal cell walls, making them less accessible for insect piercing and the germination of pathogenic fungal hyphae.

Beyond the direct protective effect, nettle acts as a potent natural elicitor. It activates the host plant's own defense proteins, allowing it to resist biotic stresses more effectively over a long period.

Preparations based on Urtica spp. also possess a disinfecting effect on the leaf surface by altering the pH environment, making it unfavorable for the development of powdery mildew spores and colonies of small sap-sucking pests.

Additionally, nettle extract serves as a foliar fertilizer. Its high chlorophyll and iron content helps intensify photosynthesis, which indirectly helps the plant recover faster from damage caused by diseases.

The primary targets for using nettle-based agents are small sap-sucking insects such as aphids, spider mites, and whiteflies, for which the plant's components act as repellents.

As a fungicidal agent, nettle is effective against powdery mildew on various vegetable and berry crops. It suppresses mycelium development in the early stages of infestation.

The use of these preparations is indicated for vegetable crops in both open and protected ground, including tomatoes, cucumbers, and cabbage, as well as for fruit trees and shrubs.

Nettle is often used to prevent fungal diseases in high-humidity conditions, where the risk of late blight or leaf spot infections increases significantly.

It is worth noting that nettle infusion also attracts beneficial entomofauna and improves the general condition of the root zone microbiota when applied as a soil drench.

To prepare a working solution, the fermentation method is most commonly used: 1 kg of fresh green mass per 10 liters of water. The solution is fermented for 3 to 14 days, depending on the desired concentration and application goals.

For foliar application (spraying) against pests, the ready infusion is diluted with clean water in a 1:20 ratio to avoid leaf burns, especially in hot, sunny weather.

For soil drenching and as a growth stimulant, more concentrated solutions in a 1:10 dilution are permitted.

The frequency of treatment is once every 7–10 days during the active plant vegetation period. Preventive treatments should begin from the moment the first true leaves appear.

It is recommended to carry out spraying during morning or evening hours. Using a freshly prepared infusion ensures maximum concentration of phytoncides, which degrade during prolonged storage.

Preparations based on nettle do not possess an instant knockdown effect; therefore, they are not suitable for emergency crop rescue during massive pest infestations.

When treating plants during the flowering phase, caution should be exercised so that the infusion's specific odor does not repel pollinators, although there is no phytotoxicity towards them.

It is not recommended to mix nettle infusion with copper-based fungicides or chemical insecticides due to the risk of altering the components' chemical properties.

Prolonged use of concentrated infusions can lead to excessive nitrogen accumulation in the soil, which promotes excessive vegetative growth to the detriment of fruit yield.

Storing working solutions in metal containers is prohibited, as metal corrosion and chemical reactions occur, which reduce the effectiveness of the active substance.