What are the characteristics and functions of metallic fungicides?

①Kuaidening: It is 33.5% Kuaidening water suspension powder. It belongs to alkaline pesticides. It has a claw-like binding action and is stable to heat and chemical action. Its action is that copper ions hinder dehydrogenase. Kuaidening has a therapeutic effect and is effective against phytophthora fungi. It can be applied directly or diluted and sprayed on the diseased areas. When using this agent, it must not be mixed with strongly acidic or strongly alkaline pesticides or fertilizers, the number of applications must not be too concentrated or frequent, and attention should be paid to the PH value of the water used, so as to avoid phytotoxicity or reduced efficacy. ②Tongmiedale: It is made by mixing 15% miedale and 61.5% alkaline copper oxychloride, 76.5% wettable powder such as jiaomielu. It belongs to alkaline pesticides. It has both preventive and therapeutic effects. It has control effects on bacterial Erwioia and fungal pathogens such as phytopthors septoria colletotrichum, has good permeability, and can kill most pathogens. Its biggest disadvantage is that application under high temperature and high humidity easily causes phytotoxicity, and continuous use easily causes resistance. When using this agent, avoid mixing it with strongly acidic or strongly alkaline fertilizers or pesticides, and before and after use there must be no residue of fertilizers such as seaweed extract on the plants. ③Copper zinc maneb: It is made by mixing 52.5% alkaline copper oxychloride with 10% zineb and 10% maneb, 72.5% copper, zinc, maneb wettable powder. It belongs to alkaline pesticides. It has preventive and therapeutic effects. It is effective against diseases caused by bacteria and most fungi, has an improving effect on symptoms of deficiency of trace elements such as copper, zinc and manganese, and is suitable as a pesticide for leaf disease control. When applied during high temperature and high humidity periods, it easily causes pest damage. If an excessive amount of spreader is added during application, the liquid easily adheres to the leaves to form spots, damages the epidermal layer of the leaves, and blocks the stomata; excessive accumulation of the agent easily causes scorching of leaf tips. It is best to use this agent alone, not mixed with strongly alkaline pesticides or fertilizers, and as far as possible use it only when the daily average temperature is above ZO°C and the weather is sunny with low humidity, so as to avoid unnecessary losses. The fungicidal action of copper-formulation pesticides is that after being sprayed on the body of Cymbidium, they form a film of the agent to prevent pathogen spores from germinating, or by means of water, rain dew and pathogen secretions dissolving copper salts, they become soluble copper ions that mutually replace normal H+, MG2+, K+ and other ions in cells, hinder dehydrogenase, and kill or prevent spore germination. Copper-formulation pesticides can enter the plant body through the stomata of the plant leaves and kill pathogens that have already invaded the plant body; relatively, they also hinder the action of plant enzymes, and chlorophyll is easily fixed, causing sudden physiological changes in the plant. Therefore, after the first use of copper agents as disease control pesticides, the plants may show performances such as darker green leaf color. With repeated continuous use, the plant physiology will show disorders. The general phytotoxicity symptoms caused by improper application of copper pesticides include leaf burn, scorching of leaf tips and leaf margins; excessive accumulation of copper pesticides in the medium easily causes root growth disorders and disordered nutrient absorption, thereby affecting the balanced growth of the whole plant.CultivationWhen growers choose pesticides for disease control, for copper-type pesticides, they must be especially careful when using them; occasionally using them once at an appropriate time and under suitable climate can promote the assimilation of Cymbidium, increase chlorophyll, prevent plant aging, and improve quality and yield.