EPA Chlorothalonil Review – Vegetable Crops Hotline

EPA Chlorothalonil Review

The Environmental Protection Agency (EPA) has published a “proposed Interim Review Decision” regarding the fungicide chlorothalonil. I only recently became aware of this review. Unfortunately, the deadline to comment is January 10, 2024. A link to comment is provided at the bottom of this article. Read on for more details.

Chlorothalonil is the common name of the active ingredient (a.i.) in many common trade names such as Agronil®, Bravo®, Echo®, Equus®, Daconil®, etc. Chlorothalonil is also included as an ingredient with many other fungicides. Chlorothalonil has the FRAC group M5, which means it has multi-sites of action. In over 60 years of use, there has never been any recorded instance of fungicide resistance because it has multi-sites of action. For this reason, chlorothalonil is an important tank mix partner and is important is alternations in the field to limit the fungicide resistance of systemic products which have single sites of action. In addition, chlorothalonil has a broad range of diseases it is effective against in contrast with many systemic fungicides.

However, chlorothalonil has some disadvantages. In general, chlorothalonil has more potential for mammalian toxicity than many of our systemic fungicides. In addition, aquatic animals may be affected by certain doses of chlorothalonil. Finally, chlorothalonil may harm bees, although fungicides, in general, are not nearly as toxic to bees as some insecticides. Much more information about the effects of chlorothalonil can be found here.

Much more information about how the EPA proposes to limit the amount of chlorothalonil applied is given in the link above. In general, however, the yearly amount of chlorothalonil that can be applied is proposed to be halved. For example, with cucurbits, Bravo Weather Stik® is now labeled for up to 15.75 lb a.i. per acre per year. The EPA proposes to reduce the amount of chlorothalonil that can be applied per year to 9 lb. a.i. per acre. If one applies Bravo Weather Stik® at the maximum rate of 2.25 lb ai/acre, then the number of applications per year would be reduced from 7 applications per year to 4. Tomatoes are now limited to 15 lb ai per acre per year. At the maximum rate, 2.1 lb ai can be applied per acre per year to tomatoes. The EPA proposes to reduce the amount of chlorothalonil a.i that can be applied per acre per year to 6.5 lb ai. Therefore, the number of applications per year would be reduced from 7 to 3 under the EPA proposal. Much more information can be found at the link above.

To comment on the proposal, use the link below. If you have questions, contact me.


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