Petroleum oils

Petroleum oils, specifically identified by CAS numbers 64742-55-8 and 64742-57-7, are highly refined mineral oils used as contact insecticides and acaricides in agricultural crop protection. These substances act as physical barriers against various pests, offering a unique mode of action that differs significantly from traditional neurotoxic synthetic pesticides.

The primary mechanism of action is physical asphyxiation. When applied as an emulsion, the oil creates a film over the pest, effectively sealing off its spiracles and preventing gas exchange, which leads to death by suffocation. Furthermore, petroleum oils provide an ovicidal effect by penetrating and disrupting the structure of insect and mite eggs, preventing successful hatching and larvae development.

Petroleum oils are mainly used on fruit trees, vines, and citrus plantations. They are highly effective against scale insects, mealybugs, mites, aphids, and psyllids. Their application is particularly valuable in early spring during the dormant stage or at the start of bud break to eliminate overwintering stages of pests hidden in tree bark crevices, thereby reducing the need for chemical sprays later in the season.

Application requires careful attention to environmental conditions. It is essential to ensure full coverage of the plant surface as the efficacy depends on direct contact. Growers should avoid spraying when temperatures are extreme—too low (risk of lack of evaporation) or too high (risk of leaf phytotoxicity). Using these oils during the dormant period is the most common practice to minimize any risk of plant stress.

Safety and handling are paramount. While petroleum oils are generally safer for non-target organisms, they should not be applied during flowering to protect pollinators. Users must wear appropriate protective equipment to avoid skin and eye irritation. Always prepare the emulsion immediately before use, ensuring the mixture is stable to avoid localized concentrations of oil that could damage tender plant tissues.