The formulation of Guotong is 30% carbendazim + 50% mancozeb, with a total content of 80%. The product performance section states:
This product is a partially systemic fungicide with a relatively long residual effect, possessing both protective and curative action.
The phrase "partially systemic" is very precise here — the systemic portion comes from carbendazim, while the protective portion comes from mancozeb. Only by understanding this division of roles can one understand how to use it properly.
Carbendazim (30%)Benzimidazoles, systemic and therapeutic. After the fungicide penetrates leaf tissues, it interferes with the formation of the spindle apparatus during fungal mitosis. Its value lies inTreatment of mycelium that has already invaded the tissue.请提供需要翻译的中文段落内容。
Mancozeb (50%)Organic sulfur compounds, multi-site protective fungicides. They interfere with multiple sulfhydryl-containing enzyme systems of pathogenic fungi, thereby inhibiting spore germination and germ tube development. Their value lies inPrevent pathogens from entering.请提供需要翻译的中文段落内容。
Disease infection has two stages:Surface germination(spores land on the leaf surface, germinate, form germ tubes, and penetrate the epidermis) andIntra-organizational expansion(Mycelium spreads between cells.)
Protectant fungicides can only block the first stage, whereas systemic fungicides act on the second stage. The reason most diseases remain uncontrolled is precisely that only one of these two fronts is addressed.
The design of this formulation addresses both fronts: mancozeb establishes a protective barrier on the surface, while carbendazim acts on the pathogen once it has entered the plant tissue.
The ratio of 30:50 is noteworthy—Protectants account for the largest share.请提供需要翻译的中文段落内容。
This determines its accurate positioning:Give priority to protective fungicides, with systemic fungicides as a supplement.Its strength lies in preventive application before disease onset or in the early stages, rather than in rescue treatment during the mid-to-late stages of disease development.
Many users treat it as a "curative agent" and only apply it after the disease has become severe, so the results are naturally unsatisfactory. The scenarios where its value can truly be realized are:Routine protection before the rainy season + rapid interception at the early stage of disease onset请提供需要翻译的中文段落内容。
Another benefit of the high proportion of mancozeb is thatResistance managementWith multi-site action and extremely low resistance risk, it can dilute the resistance selection pressure of carbendazim during application.
Only two lines are registered:
Pear scab, 640-800 times dilution, spray application.
Apple alternaria leaf spot, 640-800 fold dilution, spray application.
Both are fruit tree diseases, and the application rates for both are the same.
Pear scabIt damages leaves, fruits, and new shoots. Infected leaves develop dark green mold layers on the upper surface, while infected fruits form suberized lesions. The pathogen overwinters as mycelium in bud scales and diseased branches, releases spores after bud break in spring, and causes concentrated infection during the rainy season.
Apple tree Alternaria leaf spotIt mainly damages leaves, especially the tender leaves of spring and autumn shoots. The lesions are brown and circular; in severe cases, massive leaf defoliation occurs, affecting flower bud differentiation and fruit set. The two words "spot" and "defoliation" in the name of this disease clearly capture its two characteristics.
The control windows for both diseases are associated with new shoot growth and rainfall—the leaf expansion stage is the susceptible period, and rainfall is the trigger for spore release.
Registration technical requirements:Once every 10 days.请提供需要翻译的中文段落内容。
This interval is shorter than the 10–15 days for carbendazim alone. The reasons are as follows:
The residual efficacy of protectants is limited.Mancozeb forms a protective film on the leaf surface, which is washed off by rain, degraded by ultraviolet light, and "diluted" by newly emerging leaves. After approximately 10 days, the effectiveness of the film declines markedly.
The new shoots of fruit trees continue to grow.Once new leaves have unfolded, they are in an unprotected state. A 10-day interval can cover the unfolding rhythm of most new leaves.
High disease pressure during the rainy season.When rainfall is frequent, the pesticide film dissipates quickly; a 10-day interval is conservative yet reliable.
If the rainy season is particularly intense, in practice the spray interval is often shortened or the number of applications increased—but this must remain within the number of applications permitted under the registration, and the pre-harvest interval must be observed.
The optimal timing is before disease onset or at the early stage of infection.— For mixtures dominated by protective ingredients, this point is central. Mancozeb is only meaningful if it covers the leaf surface before spore germination, and application before rain is standard practice.
Apply the pesticide as evenly as possible, ensuring that both the upper and lower surfaces of the fruit tree leaves are covered.Spore germination does not occur only on the upper leaf surface. The lower leaf surface, with its abundant stomata and higher humidity, is in fact the entry point for many pathogens. Spraying only the upper leaf surface is tantamount to leaving half the target unprotected.
Do not apply pesticide on windy days or when rain is expected within 1 hour.Strong winds cause spray drift, while rainfall washes off the pesticide film.
Do not mix with alkaline pesticides or copper-containing formulations.This holds true for both components—carbendazim degrades under alkaline conditions, and mancozeb becomes ineffective or causes phytotoxicity when mixed with copper-based formulations or strong alkalis.
Mancozeb is sensitive to certain varieties.Some pear and persimmon cultivars are relatively sensitive to mancozeb during the young fruit stage, and fruit surface spotting may occur. For first-time use, a small-scale trial spray is recommended.
The resistance value of this combination derives from mancozeb. However, it should be noted that carbendazim belongs to the benzimidazole class and exhibits cross-resistance with thiophanate-methyl and benomyl.
It is recommended to schedule this mixture inConservation node(Before the rainy season and before disease onset), the key disease incidence period still relies primarily on fungicides with different mechanisms of action, such as triazoles and strobilurins.
