Written collaboratively by Stephen Robertson, Philip Rozeboom, Patrick Wagner, Clarence Winter, Adam Varenhorst, and Brad McManus.
The 24c SLN label for red sunflower seed weevil management in South Dakota will be effective during the growing season from July 15 through August 31. The 24c label for red sunflower seed weevil management in sunflowers will be in effect until 2030, unless revoked prior to that date. Before or after these dates, products containing the active ingredient, malathion can’t legally be applied to sunflower for red sunflower seed weevil management.
This request was submitted and approved by the Environmental Protection Agency (EPA) due to the large populations of red sunflower seed weevil present in South Dakota that are resistant to pyrethroid insecticides. As a reminder, testing has determined that red sunflower seed weevil in South Dakota have resistance to the active ingredients lambda-cyhalothrin, esfenvalerate, zeta-cypermethrin, deltamethrin, and beta-cyfluthrin. In addition, the EPA recently removed sunflower from the labels of products containing chlorpyrifos.
Approved Products
There are currently only five products containing malathion that have been approved for use in South Dakota:
- Fyfanon 57% EC (FMC Corporation)
- Fyfanon Malathion Insecticide (Helena Agri-Enterprises, LLC)
- Malathion 5 Insecticide (Winfield United)
- Drexel Malathion 5 EC (Drexel Chemical Company)
- Malathion 57 EC (Loveland Products)
A list of products and links to labels for malathion and other 24c labeled products can be found on the South Dakota Department of Agriculture and Natural Resources website.
Pyrethroid-resistance red sunflower seed weevils have not been detected in North Dakota’s sunflower production areas to date based on insecticide bioassay research over the last several years. In addition, the malathion 24c label only applies to South Dakota.
Thanks to support from the National Sunflower Association for the red sunflower seed weevil research and the South Dakota Department of Agriculture and Natural Resources for working to obtain the section 24c label for red sunflower
As a reminder, Malathion is an organophosphate insecticide that inhibits acetylcholinesterase (AChE). This active ingredient has had approval for other uses in South Dakota for several years. The South Dakota Department of Agriculture and Natural Resources recently received approval from the Environmental Protection Agency to temporarily register the use of malathion products for the management of red sunflower seed weevils in sunflowers.
Application Checklist
If you intend to use malathion products to manage red sunflower seed weevils, use the following checklist to ensure adherence to the 24c restrictions.
- Read the label: The product label must include red sunflower seed weevils in sunflower in the “Directions for Use” section to be used.
- Have a label copy: Have a copy of the 24c label readily available while making applications.
- Apply within the dates provided: The 24c label only permits use for red sunflower seed weevil management between July 15 and August 31.
- Determine bloom percentage: Sunflowers must be at 10% bloom before the first application. Use the red sunflower seed weevil economic threshold to determine enough adults are present to warrant a treatment.
- Check for beehives: Malathion is highly toxic to bees. Applications of malathion per the 24c label must occur on sunflowers between the hours of 12 a.m. and 9 a.m. or 6 p.m. and 12 a.m. Applicators must visit FieldWatch to determine the locations of the nearest beehives and communicate with the beekeepers.
- Adhere to buffer zone restrictions: Applications made Brookings, Day Deuel, Grant, Marshall, or Moody counties that are made downwind of critical habitat (rangeland, pasture, and native grasslands) for the endangered Dakota skipper or Poweshiek skipperling must have a buffer of 50 feet for aerial applications and 25 feet for ground applications.
