What should you pay attention to when applying fungicides?
What should you pay attention to when applying fungicides? Please give an introduction. When applying fungicides, pay attention to the following points: Concentration. When spraying with liquid formulations, it is often necessary to use water to prepare or dilute the agent to an appropriate concentration. Too high a concentration will cause phytotoxicity and waste, while too low a concentration will be ineffective. For some wettable powders, a small amount of water should first be added to make the powder into a paste, then...
What should you pay attention to when applying fungicides? Please give an introduction.
When applying fungicides, pay attention to the following points:
Concentration
When spraying with liquid formulations, it is often necessary to use water to prepare or dilute the agent to an appropriate concentration. Too high a concentration will cause phytotoxicity and waste, while too low a concentration will be ineffective. For some wettable powders, a small amount of water should first be added to make the powder into a paste, and then more water should be added to prepare the solution. A wetting agent may also be added during preparation.
Spraying time
Spraying too early will cause waste or reduce control efficacy, while spraying too late means a large amount of pathogens have already invaded the host, and even if systemic therapeutic agents are sprayed, the effect will be limited. Depending on the situation or based on short-term forecasts, spray in time for protection when there is no disease or just when the disease has begun.
Number of sprays
The number of sprays is mainly determined by the length of the pesticide's residual effect period and weather conditions. Generally, spray once every 10-15 days, for a total of 2-3 sprays, and spray again after rain, repeating the application.
Spraying quality
The spray volume should be appropriate. Too little cannot provide thorough protection to all parts of the plant, while too much is wasteful and may even cause phytotoxicity. Spraying requires fine droplets and uniform application, including both the upper and lower surfaces of leaves.
Phytotoxicity issues
There are many reasons why spraying causes phytotoxicity to plants. Agents with stronger water solubility are more likely to cause phytotoxicity, and different crops also have different sensitivities to agents. For example, Bordeaux mixture causes no phytotoxicity, but it can also cause phytotoxicity in copper-sensitive crops. Legumes, potatoes, and cotton are sensitive to lime sulfur mixture. Different developmental stages of crops respond differently to agents, and rice is prone to phytotoxicity during the booting and flowering stages. It is also related to weather conditions. Generally, the effects of temperature and sunlight are more obvious. High temperatures, strong sunlight, or heavy fog are more likely to cause phytotoxicity.
How to mix
Generally, pesticides that easily decompose and become ineffective when encountering alkaline substances cannot be mixed with alkaline substances. For example, alkaline fungicides such as Bordeaux mixture and lime sulfur mixture cannot be mixed with 1605. Agents that produce chemical reactions after mixing and can cause phytotoxicity also cannot be mixed and applied. For example, mixing lime sulfur mixture with 1605 will not only reduce efficacy but also cause phytotoxicity. Pesticides that cause emulsion breakdown or produce a large amount of precipitate after mixing also cannot be mixed. Which agents can or cannot be mixed can be found in the instructions.
A small number of pesticides have a synergistic effect when mixed. For example, when dimethoate is mixed with neutral and acidic fungicides such as mancozeb, wettable sulfur, and colloidal sulfur, the efficacy not only does not decrease but also increases.
Resistance issues
Long-term use of a single agent (mainly systemic fungicides) will cause pathogens to develop resistance, making the agent used ineffective. To avoid this problem, compound agents should be selected, or systemic fungicides and traditional fungicides should be mixed.
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