Potassium Phosphite As a Fungicide and Fertiliser

     Phosphorus is an essential nutrient for plant growth, but is hard to supply adequately in our soils due to its low availability.Potassium Phosphite Plants experiencing phosphorus deficiency display characteristic symptoms and/or show reduced growth, become more susceptible to pathogens or die at relatively young age. Insufficient phosphate supplies also lead to poor root health and a host of other problems. Phosphite has a direct fungitoxic effect on certain pathogens and stimulates the plants own natural defence systems capable of producing systemic acquired resistance (SAR).

     Potassium Phosphite is an metal salt of phosphorous acid, H3PO3, that can be applied as a soil drench or granule to suppress Phytophthora blight.Potassium Phosphite It is registered in some countries as a fungicide or fertilizer and is generally considered harmless in the environment. Its toxicity is lower than that of phosphorous acid and it does not leach readily from the soil.

     Research results indicate that phosphite treatment leads to rapid changes in gene expression patterns in the plant, especially those associated with primary metabolism and cell wall associated processes.potassium phosphite Physiological studies on different cultivars suggest that the effect of phosphite on tuber blight is not only cultivar specific but might be related to the degree of partial resistance.

     A combination of phosphite treatments can provide better control than conventional fungicides in potato cultivation.potassium phosphite It is suggested that this can be achieved by applying phosphite at intervals and doses adjusted to the level of partial resistance and other crop properties, such as rooting ability or leaf vigour.

     The effectiveness of phosphite in controlling blight has been demonstrated in controlled environment and field trials.potassium phosphite It was shown that phosphite triggers the rapid activation of several defence responses in potato plants. These responses not only suppress the development of blight lesions but also prime the plants to respond faster to subsequent infection by releasing compounds that directly kill the fungus or inhibit its growth and/or spread within the plant.

     This study investigated four phosphite products containing the active ingredient mono- and di-potassium salts of phosphorous acid. These were applied as a soil drench to containerized and established field-grown Rhododendron plants at the manufacturers’ recommendations.

     All phosphite products tested in this study suppressed lesion area starting 1 week post-treatment and were effective up to 6 weeks after application. These results confirm that phosphite is a promising candidate for use in the fight against late blight. It could be applied at lower rates compared to current fungicides and should therefore reduce the overall quantity of fungicide used. However, further investigation of residue levels in potatoes and determination of the optimum rate for application is required as MRLs may need to be set.