Growers seeing information on the internet about sulfur burners and evaporators have been asking about their utility for managing diseases, powdery mildew especially, in high tunnels and greenhouses. This was the topic of a webinar presentation. This article covers what was presented. Slides in the presentation pdf illustrating information presented below are noted. In addition to covering the topic, this article and the presentation provides some general information about using pesticides with specialized equipment rather than a standard boom sprayer.
Powdery mildew is an important disease of tomato, kale, and lettuce, grown under protected culture, which includes greenhouse, high tunnel, and winter tunnel. Powdery mildew fungi develop better under the drier conditions, in particular, and also lower light levels, that are typical for these protected environments compared to outdoor production (slide 2).
Sulfur fungicides are very effective for powdery mildew. In my evaluations of fungicides for powdery mildew in field-grown pumpkin, sulfur was at least as effective as chlorothalonil, another contact fungicide. Sulfur was more effective for powdery mildew on the underside of leaves reflecting sulfur’s volatility which enables some re-distribution (slide 3).
Searching the internet for burners and evaporators turns up websites where this equipment can be purchased as well as information about how to use them for controlling diseases, in particular powdery mildew. There are several potential advantages of making applications with a burner or evaporator, rather than a boom sprayer, to plants in an enclosed environment. In particular, the user does not need to be present during the application plus expected ability to obtain coverage on leaf surfaces that cannot easily be reached with a standard boom sprayer (slides 4 and 5).
Microthiol Disperss is one of many sulfur fungicides. It is the product I’ve used in my research. Like other sulfur fungicides it is labeled primarily for powdery mildew diseases on several crops, a few other diseases in particular rusts, and also mites (slide 6).
If a fungicide can be applied using specialized equipment, like a sulfur burner, in addition to a standard boom sprayer, there will be directions for this use on the label. The easiest way to determine if a fungicide can be applied in a specialized way is to download an electronic version of the label. The CDMS Label Database website has federal labels that can be downloaded (www.cdms.net/Label-Database) (slide 7). NY growers should use the state label database.
Next, open the label file and use the search command for the use. Searching a sulfur fungicide label for ‘burner’ or ‘evaporator’ turns up no results (slides 8 and 9). On the other hand, searching for ‘chemigation’ brings up the section with directions for applying the fungicide through chemigation systems (slides 10 and 11). Not only is it essential for the use to be on the label since it is a legal document, information about the use is critical for a specialized application method to know the pesticide can be applied in that way. I was not able to find an EPA registered fungicide with label directions on how to apply it with a burner or evaporator.
A company selling specialized equipment for applying a pesticide likely also has information about pesticides that can be applied using the pesticide. The company website selling burners and evaporators that I checked also sells a sulfur product to use with their equipment and it has directions on how to apply (slides 12 and 13). Is the information at the company website sufficient for making the application? No. The label for the product needs to be checked to confirm the directions. The product name but not its label was at the company website.
Searching for ‘Soil Sulfur’ at the CDMS Label Database website turned up 3 soil amendment products (slide 14).
The label downloaded from the CDMS Database is missing something essential to allow its use to control a disease or insect pest (slide 15).
It does not have either an EPA registration number, which can be found on the first page of a label for a registered pesticide below the list of ingredients. or a statement that the product qualifies for exemption from registration under FIFRA (slide 16).
FIFRA is the United States Federal Insecticide, Fungicide, and Rodenticide Act. FIFRA provides for federal regulation of pesticide distribution, sale, and use. All pesticides distributed or sold in the United States must be registered by EPA or determined by EPA to be a minimum risk pesticide that can be exempted. The registration process is not just a legal requirement. It is valuable for the user and consumers because EPA requires the company applying for a registration to show, among other things, that using the pesticide according to specifications ‘will not generally cause unreasonable adverse effects on the environment’ which is defined to include people (slide 17).
The ‘Directions for Use’ section of the Soil Sulfur label states that it is to be used as part of a nutrition system. There is no description of how to use it for disease management. Labels are legal documents which includes how they are used. This is a second reason that Soil Sulfur cannot legally be used in the United States to manage disease in a commercial crop, regardless of the application method (slides 18 and 19).
Internet search results often include a section entitled ‘People also ask’. One question that came up is ‘How do you burn sulfur for powdery mildew?’ The answer obtained by clicking on it includes description of how sulfur burners work and how long to run them. Another question is ‘Are sulfur burners dangerous?’ The answer is ‘There are no EPA-approved sulfur products for use in plant fumigation. When sulfur is burned, it turns into a gas called sulfur dioxide. The gas can mix with moisture on plants to form an acid that can damage plant leaves. Breathing the gas can be harmful to human health.’ (slides 20 and 21).
The answer includes a link to a National Pesticide Information Center webpage with more information about this topic (slide 22).
In summary, sulfur burners and evaporators cannot be legally used for managing diseases in commercial crops in greenhouses and high tunnels. However, sulfur can be used when applied using a standard boom sprayer. Labels for sulfur fungicides that can legally be applied in a greenhouse contain pertinent use instructions (slides 23 and 24).
There is a sulfur fungicide registered in Canada for application in a vaporizer. It is not registered in the U.S. and so it is not permitted to be used here.
Prepared by Margaret T McGrath. 11/30/20.