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Pyrimethanil for Gray Mold Control: Uses, Applications and Crop Safety
Sep 11,2026
Pyrimethanil is a fungicide commonly used for the control of gray mold and other fungal diseases. It has systemic activity and can move into plant tissues after application, helping the active ingredient reach areas that may be difficult to cover with spray, including flowers and young fruit.
Pyrimethanil is also relatively less affected by low temperatures than some other fungicides, making it useful in disease management during cool periods in late autumn, winter, and early spring.
In crop production, pyrimethanil is commonly used on vegetables such as cucumber and tomato, as well as on grapes for gray mold control. However, repeated use should be managed carefully because inappropriate application can increase the risk of fungicide resistance or crop injury.
How Does Pyrimethanil Work?
Pyrimethanil mainly acts by interfering with the secretion of enzymes and other substances produced by fungal pathogens that are involved in infection. This helps prevent the pathogen from successfully infecting plant tissues.
It has both protective and curative activity. After application, pyrimethanil can penetrate plant tissues and provide activity in areas that are difficult to reach directly with a spray, such as flowers and young fruit.
Main Uses of Pyrimethanil
Pyrimethanil is mainly used to manage gray mold (Botrytis cinerea) and certain other fungal diseases on a range of crops.
Its systemic activity and relatively good performance under cool conditions make it a useful option for disease management. However, application should always follow the product label and local registration requirements, as approved crops, target diseases, application rates, and pre-harvest intervals can vary by country.
Pyrimethanil Application
1. Gray Mold on Cucumber and Tomato
For the control of gray mold on cucumber, tomato, and similar vegetable crops, pyrimethanil is generally applied before disease becomes severe or during the early stage of infection.
For example, the source recommendation for a 40% pyrimethanil formulation is 25–95 g per mu, diluted with approximately 800–1,200 times water, with a spray volume of about 30–75 kg per mu. The actual rate should be adjusted according to crop size and label instructions.
Applications may be repeated at 7–10 day intervals, with 2–3 applications when necessary.
For grape gray mold, a 40% pyrimethanil suspension concentrate or wettable powder may be applied at approximately 1,000–1,500 times dilution, subject to the registered product label. For a broader approach to grape growth and crop management, see our [Grape Growth Solution].
To reduce the risk of resistance, pyrimethanil should not be relied on repeatedly throughout the same growing season. Where multiple fungicide applications are required, rotate pyrimethanil with fungicides from different modes of action.
For outdoor vegetable crops, spraying during periods with relatively low wind and cooler temperatures can help improve application conditions and reduce unnecessary spray drift.
2. Crop Injury on Eggplant
Eggplant can be sensitive to pyrimethanil under certain application conditions.
Possible symptoms of crop injury include irregular dark brown or black spots on leaves, leaf yellowing, and, in more severe cases, leaf drop. These symptoms may sometimes be mistaken for a fungal leaf spot disease.
Applying additional fungicide without identifying the cause can make the injury worse. Therefore, when symptoms appear after pyrimethanil application, it is important to distinguish possible phytotoxicity from an actual disease infection before making another application.
3. Crop Injury on Beans and Other Sensitive Legumes
Beans and some other leguminous crops may also be sensitive to pyrimethanil.
Possible symptoms include yellowing or yellow-white leaves, while severe injury may result in drying and dropping of leaves, flowers, or young fruit.
For sensitive crops such as beans and eggplant, avoid unnecessary applications and use only concentrations permitted by the registered product label.
For example, the source material gives a 600-fold dilution as a reference for the safe application of a 20% pyrimethanil powder formulation on eggplant and beans during the growing period. However, this should not be treated as a universal recommendation because formulation, crop variety, application method, climate, and local registration requirements can affect crop safety.
Resistance Management and Safe Use
Pyrimethanil should be used as part of an integrated fungicide rotation program rather than being applied repeatedly as the only gray mold treatment.
When disease control requires several fungicide applications during one growing season, rotate pyrimethanil with products having different modes of action. Always follow the registered label for the specific formulation being used, including application rate, spray interval, number of applications, target crops, and pre-harvest interval.
For more information about Pyrimethanil fungicide, please contact us on WhatsApp: +86 138 3717 2293.
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