Tar oils

Tar oils are complex mixtures of hydrocarbons and organic compounds derived from the dry distillation of wood or coal. In agronomy, they serve as contact insecticides and acaricides with a broad spectrum of activity.

Their mode of action is based on physical effects on pests. Upon contact with the insect or mite, the oil coats it in a thin film. This blocks the respiratory system (tracheae and spiracles), leading to suffocation and eventual death of the organism.

A key feature of these oils is their ability to dissolve the chitinous exoskeleton, which enhances the penetration of active components into the pest. They also exhibit a significant repellent effect, discouraging insects from settling on treated plant surfaces.

Tar oil-based products have low selectivity, meaning they affect a wide range of pests at various developmental stages. This makes them highly effective for targeting overwintering insect populations.

Unlike systemic insecticides, tar oils do not penetrate deep into plant tissues, which minimizes the risk of residue accumulation in fruits and berries, provided that application guidelines are strictly followed.

Tar oils are effectively used to suppress populations of sucking and chewing pests in orchards and berry crops. They demonstrate high efficacy against overwintering stages of pests residing on tree bark.

Primary targets for treatment include scale insects and armored scales, which are well-protected from many other chemicals by their tough outer shells. The oils penetrate under this protective layer, ensuring the mortality of the individuals.

These products also destroy eggs of spider mites and aphids, which are often laid in bark crevices or near the base of buds. This significantly reduces the pathogen and pest pressure in the orchard before the growing season begins.

The oils are used against psyllids and mealybugs, which extract sap from young shoots. Regular application allows for effective control of their numbers during the early stages of vegetation.

They are utilized to protect pome and stone fruit crops, as well as ornamental shrubs that harbor complexes of pests living in the bark throughout the winter period.

The application of tar oils is scheduled during the plant dormancy period — early spring, before bud break, or late autumn after leaf fall. The temperature must be stable, avoiding the risk of night frosts.

The application rate depends on the specific concentration of the emulsion, typically used as aqueous solutions. It is crucial to ensure thorough wetting of the entire bark surface, including second and third-order branches.

When spraying, weather conditions must be taken into account: treatment should be carried out in dry, calm weather. High humidity can reduce the efficiency of the film, while strong wind leads to uneven distribution of the solution.

It is recommended to spray during morning or evening hours to avoid rapid drying of the solution under direct sunlight, which can decrease insecticidal activity.

The frequency of application is strictly limited by the product guidelines; usually, one or two treatments per season are sufficient to achieve the required protective effect against overwintering pest stages.

The use of tar oils requires strict adherence to safety protocols. These products can be phytotoxic if application timing or concentrations are violated, potentially causing burns to buds and young tissues.

Spraying is strictly prohibited during the "green cone" phase and subsequent vegetative stages, as it may lead to foliage death and damage to fruit sets due to the blockage of gas exchange in the plants themselves.

Operators must use personal protective equipment, including gloves, goggles, and respirators, to prevent the composition from contacting skin, mucous membranes, or entering the respiratory tract.

Oils are generally incompatible with most other pesticides in a tank mix unless explicitly stated by the manufacturer. Avoid mixing with sulfur-containing products to prevent excessive chemical stress on the trees.

Storage must be handled in closed warehouse facilities, away from sources of fire, as many fractions of tar oils are highly flammable substances.