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Managing the Red Sunflower Seed Weevil

   
   
   
                 (Click on thumbnail for a bigger picture)

Oilseed and confection sunflowers that are starting to show yellow
petals must be inspected for insects that may affect seed yield and
quality.

Insects showing up at this time are the red sunflower seed weevils
and head moths.  Larvae of these insects may feed on developing
seeds and reduce seed yield and quality

The economic threshold of the red sunflower seed weevil on oilseed
sunflower is dependent on the cost of control, sunflower market value,
and plant population per acre.

For example, at $12 per acre cost chemical-plus-application, $9 per
hundred pounds oilseed market value, and 20,000 plants per acre
population, spraying with an insecticide must be considered if an
average of 8 weevils per flower are present on the field.

For confection sunflower, just one seed weevil per flower is enough
to trigger spraying of the field.

Scouting for the small (about 1/8 inch long) and orange-colored seed
weevils can be enhanced using an insect repellent containing DEET
to flush the weevils hiding between the florets in a sunflower head.

To effectively control the red sunflower seed weevil, insecticides must
be applied on or before 40% of the florets (within a sunflower head)
have shed pollen in 3 out of 10 sunflowers.  This is to prevent the
female seed weevils from laying eggs on the developing seeds.

Kindly refer to the images above to determine the pollination stages
of sunflowers.

Insecticides labeled for adult sunflower seed weevils include Asana XL
(5.8 to 9.6 fluid ounces per acre), Baythroid (1.6 to 2.8 fluid ounces per
acre), Furadan 4F (1 pint per acre), Lorsban 4E (1 to 1.5 pints per acre),
Scout X-tra (2 to 2.33 fluid ounces per acre), and Warrior (2.56 to 3.84
fluid ounces per acre).  Always read and follow label directions.

Two kinds of moths are also attracted to blooming sunflowers – the
sunflower moth (gray in color, three-quarter-inch long) and the banded
sunflower moth (yellow in color with dark band, half-inch long).  Scouting
must be done at dusk or early morning when the moths are most active.

The economic thresholds on oilseed sunflower are 2 moths per 5 plants
for the sunflower moth, and 1 moth per 2 plants for the banded sunflower
moth.

The insecticides, rates, and timing of insecticide application mentioned
above for the sunflower seed weevil also apply for the sunflower moth
and banded sunflower moth.

Web posted on August 7, 2001 by Mike Catangui

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