Aluminium silicate (kaolin)

Aluminosilicates, including kaolin, are a group of natural minerals that function primarily as physical barriers. Unlike systemic chemicals, these substances do not penetrate plant tissues.

When applied to foliage and fruit, they create a microscopic white film. This layer serves as a reflective barrier against UV and infrared light, which helps mitigate heat stress and prevent sunscald.

The mechanism against pests involves masking the host plant. Insects fail to recognize the crop as a food source due to the altered visual and tactile characteristics of the surface.

The mineral particles provide an abrasive effect on the insect's cuticle. This causes moisture loss and dehydration, making the plant surface unsuitable for feeding or survival.

Furthermore, the coating creates a physical impediment to oviposition. Many insects are unable to anchor their eggs firmly on the mineral-covered surface, which disrupts their reproductive cycle.

These substances are used against a wide range of pests, including beetles, moths, and true bugs. They are highly effective in organic and integrated pest management programs.

Key target pests include aphids, thrips, psyllids, and various mite species. The treatment also suppresses the activity of certain insects that serve as vectors for plant viruses.

Beyond pest control, the mineral film can provide benefits by reducing the incidence of certain fungal pathogens. It changes the microenvironment on the leaf surface, making it less conducive to fungal development.

Application rates depend on the crop type and the pest pressure level. High-volume spraying is typically required to ensure uniform and complete coverage of the plant canopy.

Treatments should be applied preventively, well before peak pest activity or the onset of severe heat waves. Maintaining a consistent film is essential for sustained efficacy throughout the season.

Rainfall significantly reduces the effectiveness of the treatment by washing away the mineral layer. Consequently, re-application is necessary after heavy rain events, usually every 7 to 14 days.

The main limitation is the requirement for maintaining an intact protective layer. Frequent applications may be necessary, which can increase operational costs in large-scale fields.

Excessive application density might lead to reduced photosynthetic capacity. It is critical to adhere to recommended dosage rates to maintain a balance between plant health and protection.

The white residue on harvested produce may affect marketability. Post-harvest washing or cleaning is often required, particularly for fruit crops sold in the fresh market.

Workers should wear respiratory protection during mixing and application. Prolonged inhalation of fine mineral dust can cause irritation to the respiratory system.