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Get Ready to Scout for Red Sunflower Seed Weevils (07/23/20)

Red sunflower seed weevils (RSSW) will be emerging soon as sunflower starts to flower.

Red sunflower seed weevils (RSSW) will be emerging soon as sunflower starts to flower. Please send me your reports including locality and numbers when you start finding RSSW.

Identification:  RSSW are small (⅛ inch long) weevils with a snout and reddish-orange.

Scouting:  When sampling, use the X pattern and begin counting at least 75 to 100 feet into the field to avoid field margin effects. Rub your hand rigorously across the sunflower face. Count the number of RSSW adults on 5 plants at 5 sites for a total of 25 plants per field. Scout for adults in the early blooming sunflower fields when the yellow ray petals are just beginning to show. RSSW is attracted to early blooming sunflowers, as females must imbibe pollen before laying eggs. A NDSU YouTube video is available on Scouting for Red Sunflower Seed Weevil in Sunflowers.

Scouting should continue until the economic threshold (Table 1 & 2) is reached or most plants have reached 70% pollen shed. 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.

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Janet J. Knodel

Extension Entomologist

 

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