According to the IPM Crop Survey scouts, sunflowers are in the R2-R4 crop stages. However, I expect flowering to start this week according to Janet Knodel, Extension Entomologist.
Scouting for red sunflower seed weevils (RSSW) is recommended during the early flowering stages when the yellow ray petals are just beginning to show.
RSSW is attracted to the early blooming sunflowers, as females must consume pollen before laying eggs. Continue scouting until the economic threshold is reached or most plants have reached 70% pollen shed (R5.7). At 70% pollen shed, plants are no longer susceptible for egg laying or significant damage.
On older flowering plants (after R5.7), larvae of RSSW (and banded sunflower moth larvae) will be feeding inside the seeds and protected from the insecticide.
By then, much of the feeding damage has already occurred.
Please send me your field reports including locality and numbers of red sunflower seed weevils when you start finding them.
RSSW are small (⅛ inch long), reddish-orange weevils with a snout.
When sampling, use the X pattern and begin counting at least 75 to 100 feet into the field to avoid field margin effects. Count the number of RSSW adults on 5 plants at 5 sites for a total of 25 plants.
Consult the NDSU Extension YouTube video on Scouting for Red Sunflower Seed Weevil in Sunflowers for more details.
Hettinger County Extension/ANR