Fosfito

Fosfito, also known as phosphite, is a class of phosphorus-containing compounds derived from phosphorous acid (H3PO3). The term covers phosphite salts, such as potassium phosphite, as well as non-ionic phosphite esters. Phosphites are distinct from phosphates in their oxidation state and reactivity, and they behave differently in soils and plants.

In agriculture, fosfito products are used mainly as fungicides and plant biostimulants. They are effective against oomycete pathogens such as Phytophthora and Pythium and are employed to prevent or mitigate diseases including late blight and downy mildew. Their activity stems from a combination of direct antifungal effects and the stimulation of plant defense responses, which can enhance the plant’s own resistance. Applications are typically foliar sprays or soil drenches; some formulations are used for nursery stock or trunk injections, depending on the crop and product.

Although phosphites contain phosphorus, fosfito are not considered a primary source of nutrition for crops; their phosphorus value is limited and they are used mainly for disease control rather than to meet P requirements.

Safety and regulation: fosfito products are registered pesticides with label-directed usage. They generally have low acute toxicity to humans but should be handled with appropriate precautions and in accordance with regulatory guidelines. Environmental fate depends on formulation and field conditions; phosphites can be oxidized to phosphate in the environment, and overuse or misuse can affect non-target organisms or contribute to resistance in pathogens.

See also: phosphite, potassium phosphite, oomycete management, plant defense elicitors.