Potassium phosphonate, derived from phosphorous acid, began to attract attention in the 1960s for its potential as a fungicide. In the following decades, it was discovered that it not only controlled pathogens such as Phytophthora and Pythium, but also offered a favorable environmental profile. With advances in research and formulation, potassium phosphonate established itself as a key tool in modern agriculture, valued for its efficacy and environmental safety.
Mechanisms of action of potassium phosphonate
Direct fungicidal action: Potassium phosphonate inhibits the germination and mycelial growth of pathogens, such as oomycetes, by interfering with oxidative phosphorylation. This alters the cellular composition of the pathogen, reducing disease severity in plants (Yáñez-Juárez et al., 2018; García-Velasco et al., 2020). According to Fenn and Coffey (1985), phosphorous acid also affects the structure of the fungal membrane, limiting disease progression.
2. Induction of systemic acquired resistance (SAR): Potassium phosphonate activates natural plant defenses, promoting the production of phytoalexins and pathogenesis-related proteins. This process strengthens the plant to resist future attacks and allows a broader response against diverse pathogens (Monsalve et al., 2012; Yáñez-Juárez et al., 2018). Rapid conversion to phosphorous acid and phosphonate dianion HPO₃²- (Bompeix et al., 1980) enhances systemic protection.
Application and efficiency
Potassium phosphonate is mainly applied foliarly, where it is translocated systemically both acropethically and basipetally (MoA FRAC code P07). This application ensures rapid uptake and effective protection against pathogens (Daniel & Guest, 2006; Guest & Grant, 1991). Its ability to distribute efficiently in the plant optimizes protection throughout the tissue.
Crop trials and results
Several studies have demonstrated the efficacy of potassium phosphonate on a wide range of crops. In citrus, it has significantly reduced the incidence of gummosis caused by Phytophthora ( Graham & Feichtenberger, 2015). In grapevine, it has reduced the severity of downy mildew caused by Plasmopara viticola (Reuveni et al., 2003). It has also been effective against olive leaf scab(Venturia oleaginea), Alternaria on persimmon, and Phytophthora infestans on potatoes and tomatoes, showing its ability to provide long-lasting protection against serious diseases.
Advantages of potassium phosphonate
Potassium phosphonate offers several advantages over conventional fungicides:
- Lower environmental impact: It breaks down rapidly to phosphoric acid, which is less persistent in the environment compared to other fungicides such as fosetyl-Al. This minimizes residue accumulation and reduces environmental impact (Hofgaard et al., 2010; Graham & Feichtenberger, 2015).
- SAR Induction: Provides broader and longer lasting protection by activating natural plant defenses, reducing the need for frequent applications and additional fungicides.
- Safety and efficiency: Compared to many chemical fungicides, potassium phosphonate has low toxicity to the environment and humans. It leaves no toxic residues on crops, which makes it safe for human consumption and decreases environmental impact.
Decomposition and Environmental Impact
Potassium phosphonate: It decomposes into phosphorous acid, carbon dioxide (CO₂), water (H₂O) and potassium (K⁺). It has a low environmental impact and is efficiently integrated into the soil nutrient cycle, being generally safe for the environment and human health (Hofgaard et al., 2010).
Fosetyl-Al: It decomposes into phosphorous acid, CO₂, H₂O and aluminum (Al³⁺). The aluminum residue can be persistent and toxic to plants, disrupting soil equilibrium (Graham & Feichtenberger, 2015).
Potassium phosphonate is an effective solution for crop protection, combining fungicidal action with the induction of natural resistance in plants. Its low environmental impact and ability to reduce the use of toxic chemicals make it a valuable option to promote responsible agricultural practices and contribute to a more sustainable future.
