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Malathion: Emergency crisis exemption for red sunflower seed weevil in South Dakota from Aug. 16-31

Written collaboratively by Adam Varenhorst, Philip Rozeboom, Amanda Bachmann, Patrick Wagner, Brad McManus, and Janet Knodel.

Originally Submitted: August 28, 2023

The emergency crisis exemption for Malathion has been approved for red sunflower seed weevil control in sunflowers in South Dakota from August 16-31, 2023. After August 31, 2023, this product cannot be applied to sunflower for red sunflower seed weevil management.

Red sunflower seed weevil adult.
Red sunflower seed weevil (Smicronyx fulvus). Courtesy: Frank Peairs, Colorado State University,

This request was submitted due to the pyrethroid-resistance and large populations of red sunflower seed weevils present in South Dakota’s sunflower production areas. For the last few years, South Dakota sunflower farmers have been dealing with populations of red sunflower seed weevils that do not respond to pyrethroid insecticide applications (lambda-cyhalothrin, esfenvalerate, zeta-cypermethrin have been tested). The Environmental Protection Agency decision to revoke the food tolerances of chlorpyrifos caused increased use of pyrethroids for red sunflower seed weevil and, as a result, an increase in the observances of field failures.

Pyrethroid-resistance in red sunflower seed weevils has not been detected in North Dakota’s sunflower production areas to date based on insecticide bioassay research over the last several years. However, populations have been detected throughout the sunflower production areas in South Dakota.

Thanks to support from the National Sunflower Association for the red sunflower seed weevil research.

Before Application

Before application, please consult and follow the emergency crisis exemption label for Malathion, and see the following resources from the South Dakota Department of Agriculture and Natural Resources:

Reminder: Malathion is highly toxic to bees, and, for this reason, per the emergency label, emergency applications should occur on sunflowers between 6:00 p.m. and 12:00 a.m.

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