Potassium phosphite has a high +3P content. This high content of low-valent P has a strong destructive effect on the cells and enzymes of pathogens. K2HPO3 is a novel non-pesticide control raw material, possessing the dual characteristics of both fertilizer and fungicide. It is not only rapidly absorbed and highly efficient but also very environmentally friendly. Potassium phosphite can also be mixed with various micronutrient fertilizers, but it is prone to precipitation when mixed with calcium fertilizer, leading to a decrease in fertilizer effectiveness. Below, we will briefly discuss the role and application of K2HPO3 in biological control.

I. Role

1. Potassium phosphite is used for crop disease control. The main disease-inhibiting substance is phosphite, a metabolite of potassium phosphite. It can stimulate the host plant to activate its defense system and produce antibiotics. After application, it can be absorbed by the plant's leaves and roots, transported into the plant, exerting a direct bactericidal function, and simultaneously activating the defense system, enabling the plant to develop disease resistance against invading pathogens. When pathogens invade, they can be controlled and utilized by non-pesticide control materials—phosphorous acid and phosphites. At this time, the pathogens are also recognized by plant cells, causing phosphites to activate the plant's defense system, producing plant resistance proteins and PR proteins to directly attack the pathogens. It also sends out warning signals, urging other uninfected cells to activate their defense systems, leading to an increase in polysaccharides and additional proteins to strengthen the cell wall. Thus, the pathogens are suppressed or killed by the plant's response. The disease resistance effect of phosphites is called Systemic Acquired Resistance, also known as Inducing Systemic Resistance, and belongs to a broad category of biological control.

2. The disease control mechanism of phosphites: After application to crops, they are absorbed by the leaves and roots and transported into the plant. When blight viruses invade, they stimulate the plant to produce plant resistance proteins. Experiments show that potassium phosphite has good downward mobility within the plant but poor upward mobility, and has no control effect during the storage period; it is best used to control leaf or fruit diseases. While potassium phosphite is typically metabolized into phosphate by soil microorganisms in the roots, becoming one of the plant's main fertilizers, experiments show that K₂HPO₃ cannot directly replace phosphate as a fertilizer. However, it can be applied together with phosphate for better plant growth promotion. Furthermore, the amount of potassium phosphite used for disease control is small and does not pollute the environment. Applying K₂HPO₃ to control blight can reduce pesticide use, maintain ecological balance, and ensure sustainable agricultural development.

3. Based on recent research and experiments by agricultural authorities on the control of plant diseases using K₂HPO₃, the application of potassium phosphite in disease control abroad has been affirmed in the control of oomycete damage caused by downy mildew, blight, and Pythium. Multiple studies have shown that K2HPO3 is highly effective in controlling various diseases, including: gerberas, lilies, orchids, Cymbidium goeringii, Cymbidium faberi, Oncidium florum; fruit trees such as kumquats, citrus fruits, papayas, and avocados; seedling blight, grape downy mildew, and lychee fruit blight; and vegetable diseases such as late blight of peppers, sweet peppers, tomatoes, and potatoes; downy mildew of lettuce and cruciferous vegetables; and seedling rot of Aristolochia debilis.

II. Application Method

1. Dilute this product with water and apply as a foliar spray or soil dredging.

2. Foliar spraying is best done in the early morning or evening, avoiding direct sunlight or high temperatures.

3. Do not mix with alkaline pesticides, as this may reduce fertilizer effectiveness or damage crops.

Dosage: The dilution concentration needs to be adjusted appropriately according to crop type, growth stage, and soil conditions before use. The application and dilution ratios are as follows:

Follicular spray: 1000~2000 times

Soil irrigation: 500~1000 times

Potassium phosphate is available in a variety of specifications and has a rich content. Some technical indicators can be adjusted according to the formula to meet agricultural needs, especially when compounded with trace elements such as Ca, Mg, Fe, Cu, Mn, and Zn. A scientifically sound formula is crucial for its effectiveness.